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301 | usaf | USAF (disambiguation) (wikipedia) | USAF usually refers to the United States Air Force, the aerial warfare branch of the U.S. Armed Forces.
USAF may also refer to:
United States Armed Forces itself, the military of the United States of America
United Student Aid Funds, a nonprofit corporation that works to enhance postsecondary-education preparedness, access and success
Upper Saint Anthony Falls, part of the Saint Anthony Falls
Jane's USAF, a 1999 video game
A common typo for UASF or "User Activated Soft Fork", a technique for updating Bitcoin and other blockchains
== See also ==
USSF (disambiguation)
U.S.A.A.F. - United States Army Air Force | USAF usually refers to the United States Air Force, the aerial warfare branch of the U.S. Armed Forces.
USAF may also refer to:
United States Armed Forces itself, the military of the United States of America
United Student Aid Funds, a nonprofit corporation that works to enhance postsecondary-education preparedness, access and success
Upper Saint Anthony Falls, part of the Saint Anthony Falls
Jane's USAF, a 1999 video game
A common typo for UASF or "User Activated Soft Fork", a technique for updating Bitcoin and other blockchains | 6 |
302 | usaf | United States Air Force (wikipedia) | The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal Corps, the USAF was established as a separate branch of the United States Armed Forces in 1947 with the enactment of the National Security Act of 1947. It is the second youngest branch of the United States Armed Forces and the fourth in order of precedence. The United States Air Force articulates its core missions as air supremacy, global integrated intelligence, surveillance and reconnaissance, rapid global mobility, global strike, and command and control.
The United States Air Force is a military service branch organized within the Department of the Air Force, one of the three military departments of the Department of Defense. The Air Force through the Department of the Air Force is headed by the civilian Secretary of the Air Force, who reports to the Secretary of Defense and is appointed by the President with Senate confirmation. The highest-ranking military officer in the Air Force is the Chief of Staff of the Air Force, who exercises supervision over Air Force units and serves as one of the Joint Chiefs of Staff. As directed by the Secretary of Defense and Secretary of the Air Force, certain Air Force components are assigned to unified combatant commands. Combatant commanders are delegated operational authority of the forces assigned to them, while the Secretary of the Air Force and the Chief of Staff of the Air Force retain administrative authority over their members.
Along with conducting independent air operations, the United States Air Force provides air support for land and naval forces and aids in the recovery of troops in the field. As of 2020, the service operates approximately 5,500 military aircraft and approximately 400 ICBMs. The world's largest air force, it has a $179.7 billion budget and is the second largest service branch of the U.S. Armed Forces, with 321,848 active duty airmen, 147,879 civilian personnel, 68,927 reserve airmen, 105,104 Air National Guard airmen, and approximately 65,000 Civil Air Patrol auxiliarists.
== Mission, vision, and functions ==
=== Missions ===
According to the National Security Act of 1947 (61 Stat. 502), which created the USAF:
In general, the United States Air Force shall include aviation forces both combat and service not otherwise assigned. It shall be organized, trained, and equipped primarily for prompt and sustained offensive and defensive air operations. The Air Force shall be responsible for the preparation of the air forces necessary for the effective prosecution of war except as otherwise assigned and, in accordance with integrated joint mobilization plans, for the expansion of the peacetime components of the Air Force to meet the needs of war.
Section 9062 of Title 10 US Code defines the purpose of the USAF as:
to preserve the peace and security, and provide for the defense, of the United States, the Territories, Commonwealths, and possessions, and any areas occupied by the United States;
to support national policy;
to implement national objectives;
to overcome any nations responsible for aggressive acts that imperil the peace and security of the United States.
=== Core missions ===
The five core missions of the Air Force have not changed dramatically since the Air Force became independent in 1947, but they have evolved and are now articulated as air superiority, global integrated ISR (intelligence, surveillance and reconnaissance), rapid global mobility, global strike, and command and control. The purpose of all of these core missions is to provide what the Air Force states as global vigilance, global reach, and global power.
==== Air superiority ====
Air superiority is "that degree of dominance in the air battle of one force over another which permits the conduct of operations by the former and its related land, sea, air, and special operations forces at a given time and place without prohibitive interference by the opposing force" (JP 1-02).
Offensive Counter-Air (OCA) is defined as "offensive operations to destroy, disrupt, or neutralize enemy aircraft, missiles, launch platforms, and their supporting structures and systems both before and after launch, but as close to their source as possible" (JP 1-02). OCA is the preferred method of countering air and missile threats since it attempts to defeat the enemy closer to its source and typically enjoys the initiative. OCA comprises attack operations, sweep, escort, and suppression/destruction of enemy air defense.
Defensive Counter-Air (DCA) is defined as "all the defensive measures designed to detect, identify, intercept, and destroy or negate enemy forces attempting to penetrate or attack through friendly airspace" (JP 1-02). In concert with OCA operations, a major goal of DCA operations is to provide an area from which forces can operate, secure from air and missile threats. The DCA mission comprises both active and passive defense measures. Active defense is "the employment of limited offensive action and counterattacks to deny a contested area or position to the enemy" (JP 1-02). It includes both ballistic missile defense and airborne threat defense and encompasses point defense, area defense, and high-value airborne asset defense. Passive defense is "measures taken to reduce the probability of and to minimize the effects of damage caused by hostile action without the intention of taking the initiative" (JP 1-02). It includes detection and warning; chemical, biological, radiological, and nuclear defense; camouflage, concealment, and deception; hardening; reconstitution; dispersion; redundancy; and mobility, counter-measures, and stealth.
Airspace control is "a process used to increase operational effectiveness by promoting the safe, efficient, and flexible use of airspace" (JP 1-02). It promotes the safe, efficient, and flexible use of airspace, mitigates the risk of fratricide, enhances both offensive and defensive operations, and permits greater agility of air operations as a whole. It both deconflicts and facilitates the integration of joint air operations.
==== Global integrated ISR ====
Global integrated intelligence, surveillance, and reconnaissance (ISR) is the synchronization and integration of the planning and operation of sensors, assets, and processing, exploitation, dissemination systems across the globe to conduct current and future operations.
Planning and directing is "the determination of intelligence requirements, development of appropriate intelligence architecture, preparation of a collection plan, and issuance of orders and requests to information collection agencies" (JP 2-01, Joint and National Intelligence Support to Military Operations). These activities enable the synchronization and integration of collection, processing, exploitation, analysis, and dissemination activities/resources to meet information requirements of national and military decision-makers.
Collection is "the acquisition of information and the provision of this information to processing elements" (JP 2-01). It provides the ability to obtain required information to satisfy intelligence needs (via use of sources and methods in all domains). Collection activities span the Range of Military Operations (ROMO).
Processing and exploitation is "the conversion of collected information into forms suitable to the production of intelligence" (JP 2-01). It provides the ability to transform, extract, and make available collected information suitable for further analysis or action across the ROMO.
Analysis and production is "the conversion of processed information into intelligence through the integration, evaluation, analysis, and interpretation of all source data and the preparation of intelligence products in support of known or anticipated user requirements" (JP 2-01). It provides the ability to integrate, evaluate, and interpret information from available sources to create a finished intelligence product for presentation or dissemination to enable increased situational awareness.
Dissemination and integration is "the delivery of intelligence to users in a suitable form and the application of the intelligence to appropriate missions, tasks, and functions" (JP 2-01). It provides the ability to present information and intelligence products across the ROMO enabling understanding of the operational environment to military and national decision-makers.
==== Rapid global mobility ====
Rapid global mobility is the timely deployment, employment, sustainment, augmentation, and redeployment of military forces and capabilities across the ROMO. It provides joint military forces the capability to move from place to place while retaining the ability to fulfill their primary mission. Rapid Global Mobility is essential to virtually every military operation, allowing forces to reach foreign or domestic destinations quickly, thus seizing the initiative through speed and surprise.
Airlift is "operations to transport and deliver forces and materiel through the air in support of strategic, operational, or tactical objectives" (Annex 3–17, Air Mobility Operations). The rapid and flexible options afforded by airlift allow military forces and national leaders the ability to respond and operate in a variety of situations and time frames. The global reach capability of airlift provides the ability to apply US power worldwide by delivering forces to crisis locations. It serves as a US presence that demonstrates resolve and compassion in humanitarian crisis.
Air refueling is "the refueling of an aircraft in flight by another aircraft" (JP 1-02). Air refueling extends presence, increases range, and serves as a force multiplier. It allows air assets to more rapidly reach any trouble spot around the world with less dependence on forward staging bases or overflight/landing clearances. Air refueling significantly expands the options available to a commander by increasing the range, payload, persistence, and flexibility of receiver aircraft.
Aeromedical evacuation is "the movement of patients under medical supervision to and between medical treatment facilities by air transportation" (JP 1-02). JP 4-02, Health Service Support, further defines it as "the fixed wing movement of regulated casualties to and between medical treatment facilities, using organic and/or contracted mobility airframes, with aircrew trained explicitly for this mission." Aeromedical evacuation forces can operate as far forward as fixed-wing aircraft are able to conduct airland operations.
==== Global strike ====
Global precision attack is the ability to hold at risk or strike rapidly and persistently, with a wide range of munitions, any target and to create swift, decisive, and precise effects across multiple domains.
Strategic attack is defined as "offensive action specifically selected to achieve national strategic objectives. These attacks seek to weaken the adversary's ability or will to engage in conflict, and may achieve strategic objectives without necessarily having to achieve operational objectives as a precondition" (Annex 3–70, Strategic Attack).
Air Interdiction is defined as "air operations conducted to divert, disrupt, delay, or destroy the enemy's military potential before it can be brought to bear effectively against friendly forces, or to otherwise achieve JFC objectives. Air Interdiction is conducted at such distance from friendly forces that detailed integration of each air mission with the fire and movement of friendly forces is not required" (Annex 3-03, Counterland Operations).
Close Air Support is defined as "air action by fixed- and rotary-winged aircraft against hostile targets that are in close proximity to friendly forces and which require detailed integration of each air mission with the fire and movement of those forces" (JP 1-02). This can be as a pre-planned event or on demand from an alert posture (ground or airborne). It can be conducted across the ROMO.
The purpose of nuclear deterrence operations (NDO) is to operate, maintain, and secure nuclear forces to achieve an assured capability to deter an adversary from taking action against vital US interests. In the event deterrence fails, the US should be able to appropriately respond with nuclear options. The sub-elements of this function are:
Assure/Dissuade/Deter is a mission set derived from the Air Force's readiness to carry out the nuclear strike operations mission as well as from specific actions taken to assure allies as a part of extended deterrence. Dissuading others from acquiring or proliferating WMD and delivering them contributes to promoting security and is also an integral part of this mission. Moreover, different deterrence strategies are required to deter various adversaries, whether they are a nation state, or non-state/transnational actor. The Air Force maintains and presents credible deterrent capabilities through successful visible demonstrations and exercises that assure allies, dissuade proliferation, deter potential adversaries from actions that threaten US national security or the populations, and deploy military forces of the US, its allies, and friends.
Nuclear strike is the ability of nuclear forces to rapidly and accurately strike targets which the enemy holds dear in a devastating manner. If a crisis occurs, rapid generation and, if necessary, deployment of nuclear strike capabilities will demonstrate US resolve and may prompt an adversary to alter the course of action deemed threatening to our national interest. Should deterrence fail, the President may authorize a precise, tailored response to terminate the conflict at the lowest possible level and lead to a rapid cessation of hostilities. Post-conflict, regeneration of a credible nuclear deterrent capability will deter further aggression. The Air Force may present a credible force posture in either the Continental United States, within a theater of operations, or both to effectively deter the range of potential adversaries envisioned in the 21st century. This requires the ability to engage targets globally using a variety of methods; therefore, the Air Force should possess the ability to induct, train, assign, educate and exercise individuals and units to rapidly and effectively execute missions that support US NDO objectives. Finally, the Air Force regularly exercises and evaluates all aspects of nuclear operations to ensure high levels of performance.
Nuclear surety ensures the safety, security and effectiveness of nuclear operations. Because of their political and military importance, destructive power, and the potential consequences of an accident or unauthorized act, nuclear weapons and nuclear weapon systems require special consideration and protection against risks and threats inherent in their peacetime and wartime environments. In conjunction with other entities within the Departments of Defense or Energy, the Air Force achieves a high standard of protection through a stringent nuclear surety program. This program applies to materiel, personnel, and procedures that contribute to the safety, security, and control of nuclear weapons, thus assuring no nuclear accidents, incidents, loss, or unauthorized or accidental use (a Broken Arrow incident). The Air Force continues to pursue safe, secure and effective nuclear weapons consistent with operational requirements. Adversaries, allies, and the American people must be highly confident of the Air Force's ability to secure nuclear weapons from accidents, theft, loss, and accidental or unauthorized use. This day-to-day commitment to precise and reliable nuclear operations is the cornerstone of the credibility of the NDO mission. Positive nuclear command, control, communications; effective nuclear weapons security; and robust combat support are essential to the overall NDO function.
==== Command and control ====
Command and control is "the exercise of authority and direction by a properly designated commander over assigned and attached forces in the accomplishment of the mission. Command and control functions are performed through an arrangement of personnel, equipment, communications, facilities, and procedures employed by a commander in planning, directing, coordinating, and controlling forces and operations in the accomplishment of the mission" (JP 1-02). This core function includes all of the C2-related capabilities and activities associated with air, cyberspace, nuclear, and agile combat support operations to achieve strategic, operational, and tactical objectives.
At the strategic level command and control, the US determines national or multinational security objectives and guidance, and develops and uses national resources to accomplish these objectives. These national objectives in turn provide the direction for developing overall military objectives, which are used to develop the objectives and strategy for each theater.
At the operational level command and control, campaigns and major operations are planned, conducted, sustained, and assessed to accomplish strategic goals within theaters or areas of operations. These activities imply a broader dimension of time or space than do tactics; they provide the means by which tactical successes are exploited to achieve strategic and operational objectives.
Tactical Level Command and Control is where individual battles and engagements are fought. The tactical level of war deals with how forces are employed, and the specifics of how engagements are conducted and targets attacked. The goal of tactical level C2 is to achieve commander's intent and desired effects by gaining and keeping offensive initiative.
== History ==
The U.S. War Department created the first antecedent of the U.S. Air Force, as a part of the U.S. Army, on 1 August 1907, which through a succession of changes of organization, titles, and missions advanced toward eventual independence 40 years later. In World War II, almost 68,000 U.S. airmen died helping to win the war, with only the infantry suffering more casualties. In practice, the U.S. Army Air Forces (USAAF) was virtually independent of the Army during World War II, and in virtually every way functioned as an independent service branch, but airmen still pressed for formal independence. The National Security Act of 1947 was signed on 26 July 1947, which established the Department of the Air Force, but it was not until 18 September 1947, when the first secretary of the Air Force, W. Stuart Symington, was sworn into office that the Air Force was officially formed as an independent service branch.
The act created the National Military Establishment (renamed Department of Defense in 1949), which was composed of three subordinate Military Departments, namely the Department of the Army, the Department of the Navy, and the newly created Department of the Air Force. Prior to 1947, the responsibility for military aviation was shared between the Army Air Forces and its predecessor organizations (for land-based operations), the Navy (for sea-based operations from aircraft carriers and amphibious aircraft), and the Marine Corps (for close air support of Marine Corps operations). The 1940s proved to be important for military aviation in other ways as well. In 1947, Air Force Captain Chuck Yeager broke the sound barrier in his X-1 rocket-powered aircraft, beginning a new era of aeronautics in America.
=== Antecedents ===
The predecessor organizations in the Army of today's Air Force are:
Aeronautical Division, Signal Corps (1 August 1907 – 18 July 1914)
Aviation Section, Signal Corps (18 July 1914 – 20 May 1918)
Division of Military Aeronautics (20 May 1918 to 24 May 1918)
U.S. Army Air Service (24 May 1918 to 2 July 1926)
U.S. Army Air Corps (2 July 1926 to 20 June 1941) and
U.S. Army Air Forces (20 June 1941 to 18 September 1947)
=== 21st century ===
During the early 2000s, two USAF aircraft procurement projects took longer than expected, the KC-X and F-35 programs. As a result, the USAF was setting new records for average aircraft age.
Since 2005, the USAF has placed a strong focus on the improvement of Basic Military Training (BMT) for enlisted personnel. While the intense training has become longer, it also has shifted to include a deployment phase. This deployment phase, now called the BEAST, places the trainees in a simulated combat environment that they may experience once they deploy. While the trainees do tackle the massive obstacle courses along with the BEAST, the other portions include defending and protecting their base of operations, forming a structure of leadership, directing search and recovery, and basic self aid buddy care. During this event, the Military Training Instructors (MTI) act as mentors and opposing forces in a deployment exercise. In November 2022, the USAF announced that it will discontinue BEAST and replace it with another deployment training program called PACER FORGE.
In 2007, the USAF undertook a Reduction-in-Force (RIF). Because of budget constraints, the USAF planned to reduce the service's size from 360,000 active duty personnel to 316,000. The size of the active duty force in 2007 was roughly 64% of that of what the USAF was at the end of the first Gulf War in 1991. However, the reduction was ended at approximately 330,000 personnel in 2008 in order to meet the demand signal of combatant commanders and associated mission requirements. These same constraints have seen a sharp reduction in flight hours for crew training since 2005 and the Deputy Chief of Staff for Manpower and Personnel directing Airmen's Time Assessments.
On 5 June 2008, Secretary of Defense Robert Gates accepted the resignations of both the Secretary of the Air Force, Michael Wynne, and the Chief of Staff of the Air Force, General T. Michael Moseley. In his decision to fire both men Gates cited "systemic issues associated with... declining Air Force nuclear mission focus and performance". Left unmentioned by Gates was that he had repeatedly clashed with Wynne and Moseley over other important non-nuclear related issues to the service. This followed an investigation into two incidents involving mishandling of nuclear weapons: specifically a nuclear weapons incident aboard a B-52 flight between Minot AFB and Barksdale AFB, and an accidental shipment of nuclear weapons components to Taiwan. To put more emphasis on nuclear assets, the USAF established the nuclear-focused Air Force Global Strike Command on 24 October 2008, which later assumed control of all USAF bomber aircraft.
On 26 June 2009, the USAF released a force structure plan that cut fighter aircraft and shifted resources to better support nuclear, irregular and information warfare. On 23 July 2009, The USAF released their Unmanned Aerial System (UAS) Flight Plan, detailing Air Force UAS plans through 2047. One third of the planes that the USAF planned to buy in the future were to be unmanned. According to Air Force Chief Scientist, Greg Zacharias, the USAF anticipates having hypersonic weapons by the 2020s, hypersonic unmanned aerial vehicles (also known as remotely-piloted vehicles, or RPAs) by the 2030s and recoverable hypersonic RPAs aircraft by the 2040s. The USAF intends to deploy a Sixth-generation jet fighter by the mid-2030s.
On 22 October 2023, the USAF conducted its first-ever trilateral exercise with the South Korean and Japanese air forces near the Korean Peninsula. On 29 November 2023, a USAF Bell Boeing V-22 Osprey crashed in the Japan island of Yakushima killing 1 airman.
=== Conflicts ===
The United States Air Force has been involved in many wars, conflicts and operations using military air operations. The USAF possesses the lineage and heritage of its predecessor organizations, which played a pivotal role in U.S. military operations since 1907:
Mexican Expedition as Aviation Section, U.S. Signal Corps
World War I as Aviation Section, U.S. Signal Corps and United States Army Air Service
World War II as United States Army Air Forces
Cold War
Korean War
Vietnam War
Contemporary Historical Examination of Current Operations (CHECO)
Operation Eagle Claw (1980 Iranian hostage rescue)
Operation Urgent Fury (1983 US invasion of Grenada)
Operation El Dorado Canyon (1986 US Bombing of Libya)
Operation Just Cause (1989–1990 US invasion of Panama)
Gulf War (1990–1991)
Operation Desert Shield (1990–1991)
Operation Desert Storm (1991)
Operation Southern Watch (1992–2003 Iraq no-fly zone)
Operation Deliberate Force (1995 NATO bombing in Bosnia and Herzegovina)
Operation Northern Watch (1997–2003 Iraq no-fly zone)
Operation Desert Fox (1998 bombing of Iraq)
Operation Allied Force (1999 NATO bombing of Yugoslavia)
Afghanistan War (2001–2021)
Operation Enduring Freedom (2001–2014)
Operation Freedom's Sentinel (2015–2021)
Iraq War (2003–2011)
Operation Iraqi Freedom (2003–2010)
Operation New Dawn (2010–2011)
Operation Odyssey Dawn (2011 Libyan no-fly zone)
Operation Inherent Resolve (2014–present: intervention against the Islamic State of Iraq and the Levant)
In addition since the USAF dwarfs all other U.S. and allied air components, it often provides support for allied forces in conflicts to which the United States is otherwise not involved, such as the 2013 French campaign in Mali.
=== Humanitarian operations ===
The USAF has also taken part in numerous humanitarian operations. Some of the more major ones include the following:
Berlin Airlift (Operation Vittles), 1948–1949
Operation Safe Haven, 1956–1957
Operations Babylift, New Life, Frequent Wind, and New Arrivals, 1975
Operation Provide Comfort, 1991
Operation Sea Angel, 1991
Operation Provide Hope, 1992–1993
Operation Provide Promise, 1992–1996
Operation Unified Assistance, December 2004 – April 2005
Operation Unified Response, 14 January 2010 – 22 March 2010
Operation Tomodachi, 12 March 2011 – 1 May 2011
== Culture ==
The culture of the United States Air Force is primarily driven by pilots, at first those piloting bombers (driven originally by the Bomber Mafia), followed by fighters (Fighter Mafia).
In response to a 2007 United States Air Force nuclear weapons incident, Secretary of Defense Robert Gates accepted in June 2009 the resignations of Secretary of the Air Force Michael Wynne and the Chief of Staff of the Air Force General T. Michael Moseley. Moseley's successor, General Norton A. Schwartz, a former airlift and special operations pilot, was the first officer appointed to that position who did not have a background as a fighter or bomber pilot. The Washington Post reported in 2010 that General Schwartz began to dismantle the rigid class system of the USAF, particularly in the officer corps.
In 2014, following morale and testing/cheating scandals in the Air Force's missile launch officer community, Secretary of the Air Force Deborah Lee James admitted that there remained a "systemic problem" in the USAF's management of the nuclear mission.
Daniel L. Magruder Jr. defines USAF culture as a combination of the rigorous application of advanced technology, individualism and progressive airpower theory. Major General Charles J. Dunlap Jr. adds that the U.S. Air Force's culture also includes an egalitarianism bred from officers perceiving themselves as their service's principal "warriors" working with small groups of enlisted airmen either as the service crew or the onboard crew of their aircraft. Air Force officers have never felt they needed the formal social "distance" from their enlisted force that is common in the other U.S. armed services. Although the paradigm is changing, for most of its history, the Air Force, completely unlike its sister services, has been an organization in which mostly its officers fought, not its enlisted force, the latter being primarily a rear echelon support force. When the enlisted force did go into harm's way, such as crew members of multi-crewed aircraft, the close comradeship of shared risk in tight quarters created traditions that shaped a somewhat different kind of officer/enlisted relationship than exists elsewhere in the military.
Cultural and career issues in the U.S. Air Force have been cited as one of the reasons for the shortfall in needed UAV operators. In spite of demand for UAVs or drones to provide round the clock coverage for American troops during the Iraq War, the USAF did not establish a new career field for piloting them until the last year of that war and in 2014 changed its RPA training syllabus again, in the face of large aircraft losses in training, and in response to a GAO report critical of handling of drone programs. Paul Scharre has reported that the cultural divide between the USAF and US Army has kept both services from adopting each other's drone handling innovations.
Many of the U.S. Air Force's formal and informal traditions are an amalgamation of those taken from the Royal Air Force (e.g., dining-ins/mess nights) or the experiences of its predecessor organizations such as the U.S. Army Air Service, U.S. Army Air Corps and the U.S. Army Air Forces. Some of these traditions range from "Friday Name Tags" in flying units to an annual "Mustache Month". The use of "challenge coins" dates back to World War I when a member of one of the aero squadrons bought his entire unit medallions with their emblem, while another cultural tradition unique to the Air Force is the "roof stomp", practiced by Airmen to welcome a new commander or to commemorate another event, such as a retirement.
== Organization ==
=== Administrative organization ===
The Department of the Air Force is one of three military departments within the Department of Defense, and is managed by the civilian Secretary of the Air Force, under the authority, direction, and control of the Secretary of Defense. The senior officials in the Office of the Secretary are the Under Secretary of the Air Force, four Assistant Secretaries of the Air Force and the General Counsel, all of whom are appointed by the President with the advice and consent of the Senate. The senior uniformed leadership in the Air Staff is made up of the Chief of Staff of the Air Force and the Vice Chief of Staff of the Air Force.
The directly subordinate commands and units are named Field Operating Agency (FOA), Direct Reporting Unit (DRU), and the currently unused Separate Operating Agency.
The Major Command (MAJCOM) is the superior hierarchical level of command. Including the Air Force Reserve Command, as of 30 September 2006, USAF has ten major commands. The Numbered Air Force (NAF) is a level of command directly under the MAJCOM, followed by Operational Command (now unused), Air Division (also now unused), Wing, Group, Squadron, and Flight.
=== Air Force structure and organization ===
Headquarters, United States Air Force (HQ USAF):
The major components of the U.S. Air Force, as of 28 August 2015, are the following:
Active duty forces
57 flying wings and 55 non-flying wings
nine flying groups, eight non-flying groups
134 flying squadrons
Air Force Reserve Command
35 flying wings
four flying groups
67 flying squadrons
Air National Guard
89 flying wings
101 flying squadrons
The USAF, including its Air Reserve Component (e.g., Air Force Reserve + Air National Guard), possesses a total of 302 flying squadrons.
=== Operational organization ===
The organizational structure as shown above is responsible for the peacetime organization, equipping, and training of air units for operational missions. When required to support operational missions, the Secretary of Defense (SECDEF) directs the Secretary of the Air Force (SECAF) to execute a Change in Operational Control (CHOP) of these units from their administrative alignment to the operational command of a Regional Combatant commander (CCDR). In the case of AFSPC, AFSOC, PACAF, and USAFE units, forces are normally employed in-place under their existing CCDR. Likewise, AMC forces operating in support roles retain their componency to USTRANSCOM unless chopped to a Regional CCDR.
==== Air Expeditionary Task Force ====
"Chopped" units are referred to as forces. The top-level structure of these forces is the Air Expeditionary Task Force (AETF). The AETF is the Air Force presentation of forces to a CCDR for the employment of Air Power. Each CCDR is supported by a standing Component Numbered Air Force (C-NAF) to provide planning and execution of air forces in support of CCDR requirements. Each C-NAF consists of a Commander, Air Force Forces (COMAFFOR) and AFFOR/A-staff, and an Air Operations Center (AOC). As needed to support multiple Joint Force Commanders (JFC) in the CCMD's Area of Responsibility (AOR), the C-NAF may deploy Air Component Coordinate Elements (ACCE) to liaise with the JFC. If the Air Force possesses the preponderance of air forces in a JFC's area of operations, the COMAFFOR will also serve as the Joint Forces Air Component Commander (JFACC).
==== Commander, Air Force Forces ====
The Commander, Air Force Forces (COMAFFOR) is the senior USAF officer responsible for the employment of air power in support of JFC objectives. The COMAFFOR has a special staff and an A-Staff to ensure assigned or attached forces are properly organized, equipped, and trained to support the operational mission.
==== Air Operations Center ====
The Air Operations Center (AOC) is the JFACC's Command and Control (C2) center. Several AOCs have been established throughout the Air Force worldwide. These centers are responsible for planning and executing air power missions in support of JFC objectives.
==== Air Expeditionary Wings/Groups/Squadrons ====
The AETF generates air power to support CCMD objectives from Air Expeditionary Wings (AEW) or Air Expeditionary Groups (AEG). These units are responsible for receiving combat forces from Air Force MAJCOMs, preparing these forces for operational missions, launching and recovering these forces, and eventually returning forces to the MAJCOMs. Theater Air Control Systems control employment of forces during these missions.
== Personnel ==
The classification of any USAF job for officers or enlisted airmen is the Air Force Specialty Code (AFSC).
AFSCs range from officer specialties such as pilot, combat systems officer, special tactics, nuclear and missile operations, intelligence, cyberspace operations, judge advocate general (JAG), medical doctor, nurse or other fields, to various enlisted specialties. The latter range from flight combat operations such as loadmaster, to working in a dining facility to ensure that Airmen are properly fed. There are additional occupational fields such as computer specialties, mechanic specialties, enlisted aircrew, communication systems, cyberspace operations, avionics technicians, medical specialties, civil engineering, public affairs, hospitality, law, drug counseling, mail operations, security forces, and search and rescue specialties.
Beyond combat flight crew personnel, other combat USAF AFSCs are Special Tactics Officer, Explosive Ordnance Disposal (EOD), Combat Rescue Officer, Pararescue, Security Forces, Combat Control, Tactical Air Control Party, Special Operations Weather Technician.
Nearly all enlisted career fields are "entry level", meaning that the USAF provides all training. Some enlistees are able to choose a particular field, or at least a field before actually joining, while others are assigned an AFSC at Basic Military Training (BMT). After BMT, new enlisted airmen attend a technical training school where they learn their particular AFSC. Second Air Force, a part of Air Education and Training Command, is responsible for nearly all enlisted technical training.
Training programs vary in length; for example, 3M0X1 (Services) has 29 days of tech school training, while 3E8X1 (Explosive Ordnance Disposal) is one year of training with a preliminary school and a main school consisting of over ten separate divisions, sometimes taking students close to two years to complete. Officer technical training conducted by Second Air Force can also vary by AFSC, while flight training for aeronautically rated officers conducted by AETC's Nineteenth Air Force can last well in excess of one year.
USAF rank is divided between enlisted airmen, non-commissioned officers, and commissioned officers, and ranges from the enlisted Airman Basic (E-1) to the commissioned officer rank of General (O-10), however in times of war officers may be appointed to the higher grade of General of the Air Force. Enlisted promotions are granted based on a combination of test scores, years of experience, and selection board approval while officer promotions are based on time-in-grade and a promotion selection board. Promotions among enlisted personnel and non-commissioned officers are generally designated by increasing numbers of insignia chevrons. Commissioned officer rank is designated by bars, oak leaves, a silver eagle, and anywhere from one to five stars. General of the Air Force Henry "Hap" Arnold is the only individual in the history of the US Air Force to attain the rank of five-star general.
As of 30 June 2017, 70% of the Air Force is White, 15% Black and 4.8% Asian. The average age is 35 and 21% of its members are female.
=== Commissioned officers ===
The commissioned officer ranks of the USAF are divided into three categories: company grade officers, field grade officers, and general officers. Company grade officers are those officers in pay grades O-1 to O-3, while field grade officers are those in pay grades O-4 to O-6, and general officers are those in pay grades of O-7 and above.
Air Force officer promotions are governed by the Defense Officer Personnel Management Act of 1980 and its companion Reserve Officer Personnel Management Act (ROPMA) for officers in the Air Force Reserve and the Air National Guard. DOPMA also establishes limits on the number of officers that can serve at any given time in the Air Force. Currently, promotion from second lieutenant to first lieutenant is virtually guaranteed after two years of satisfactory service. The promotion from first lieutenant to captain is competitive after successfully completing another two years of service, with a selection rate varying between 99% and 100%. Promotion to major through major general is through a formal selection board process, while promotions to lieutenant general and general are contingent upon nomination to specific general officer positions and subject to U.S. Senate approval.
During the board process, an officer's record is reviewed by a selection board at the Air Force Personnel Center at Randolph Air Force Base in San Antonio, Texas. At the 10 to 11-year mark, captains will take part in a selection board to major. If not selected, they will meet a follow-on board to determine if they will be allowed to remain in the Air Force. Promotion from major to lieutenant colonel is similar and occurs approximately between the fourteen year and the fifteen year mark, where a certain percentage of majors will be in zone (i.e., "on time") or above zone (i.e., "late") for promotion to lieutenant colonel. This process will repeat at the 18-year mark to the 21-year mark for promotion to full colonel.
The Air Force has the largest ratio of general officers to total strength of all of the U.S. Armed Forces and this ratio has continued to increase even as the force has shrunk from its Cold War highs.
=== Warrant officers ===
Although provisions were made in Title 10 of the United States Code for the Secretary of the Air Force to appoint warrant officers, the Air Force had not used warrant officer grades for many years, and, along with the Space Force, were the only U.S. Armed Services not to do so until 2024. The Air Force inherited warrant officer ranks from the Army at its inception in 1947. The Air Force stopped appointing warrant officers in 1959, the same year the first promotions were made to the new top enlisted grade, Chief Master Sergeant. Most of the existing Air Force warrant officers entered the commissioned officer ranks during the 1960s, but small numbers continued to exist in the warrant officer grades for the next 21 years.
The last active duty Air Force warrant officer, CWO4 James H. Long, retired in 1980, and the last Air Force Reserve warrant officer, CWO4 Bob Barrow, retired in 1992. Upon his retirement, he was honorarily promoted to CWO5, the only person in the Air Force ever to hold this grade. Since Barrow's retirement, the Air Force warrant officer ranks, while still authorized by law, were not used.
It was announced at the AFA Warfare Symposium on February 12, 2024, that warrant officer ranks in the cyber and information technology fields would be reintroduced, beginning in FY25. It was stated that this effort was to retain talent in these technical fields for airmen who did not wish to pursue a leadership path. An initial class of 30 warrant officers 1s to begin training in the summer 2024.
=== Enlisted airmen ===
Enlisted airmen have pay grades from E-1 (entry level) to E-9 (senior enlisted). While all USAF personnel, enlisted and officer, are referred to as airmen, in the same manner that all Army personnel, enlisted and officer, are referred to as soldiers, the term also refers to the pay grades of E-1 through E-4, which are below the level of non-commissioned officers (NCOs). Above the pay grade of E-4 (i.e., pay grades E-5 through E-9) all ranks fall into the category of NCO and are further subdivided into "NCOs" (pay grades E-5 and E-6) and "senior NCOs" (pay grades E-7 through E-9); the term "junior NCO" is sometimes used to refer to staff sergeants and technical sergeants (pay grades E-5 and E-6).
The USAF is the only branch of the U.S. military where NCO status is achieved when an enlisted person reaches the pay grade of E-5. In all other branches, NCO status is generally achieved at the pay grade of E-4 (e.g., a corporal in the Army and Marine Corps, Petty Officer Third Class in the Navy and Coast Guard). The Air Force mirrored the Army from 1976 to 1991 with an E-4 being either a senior airman wearing three stripes without a star or a sergeant (referred to as "buck sergeant"), which was noted by the presence of the central star and considered an NCO. Despite not being an NCO, a senior airman who has completed Airman Leadership School can be a supervisor according to the AFI 36–2618.
=== Uniforms ===
The first USAF dress uniform, in 1947, was dubbed and patented "Uxbridge blue" after "Uxbridge 1683 blue", developed at the former Bachman-Uxbridge Worsted Company. The current service dress uniform, which was adopted in 1994, consists of a three-button coat with decorative pockets, matching trousers, and either a service cap or flight cap, all in Shade 1620, "Air Force blue" (a darker purplish-blue). This is worn with a light blue shirt (shade 1550) and shade 1620 herringbone patterned necktie. Silver "U.S." pins are worn on the collar of the coat, with a surrounding silver ring for enlisted airmen. Enlisted airmen wear sleeve rank on both the jacket and shirt, while officers wear metal rank insignia pinned onto the epaulet loops on the coat, and Air Force blue slide-on epaulet loops on the shirt. USAF personnel assigned to base honor guard duties wear, for certain occasions, a modified version of the standard service dress uniform that includes silver trim on the sleeves and trousers, with the addition of a ceremonial belt (if necessary), service cap with silver trim and Hap Arnold Device (instead of the seal of the United States worn on the regular cap), and a silver aiguillette placed on the left shoulder seam and all devices and accoutrements.
The Airman Combat Uniform (ACU) in the Operational Camouflage Pattern (OCP) replaced the previous Airman Battle Uniform (ABU) on 1 October 2018.
=== Awards and badges ===
In addition to basic uniform clothing, various badges are used by the USAF to indicate a billet assignment or qualification-level for a given assignment. Badges can also be used as merit-based or service-based awards. Over time, various badges have been discontinued and are no longer distributed.
=== Training ===
All enlisted Airmen attend Basic Military Training (BMT) at Lackland Air Force Base in San Antonio, Texas for 7+1⁄2 weeks. Individuals who have prior service of over 24 months of active duty in the other service branches who seek to enlist in the Air Force must go through a 10-day Air Force familiarization course rather than enlisted BMT, however prior service opportunities are severely limited.
Officers may be commissioned upon graduation from the United States Air Force Academy, upon graduation from another college or university through the Air Force Reserve Officer Training Corps (AFROTC) program, or through the Air Force Officer Training School (OTS). OTS, located at Maxwell Air Force Base in Montgomery, Alabama since 1993, in turn encompasses two separate commissioning programs: Basic Officer Training (BOT), which is for officer candidates for the Regular Air Force and the Air Force Reserve; and the Academy of Military Science (AMS), which is for officer candidates of the Air National Guard.
The Air Force also provides Commissioned Officer Training (COT) for officers of all three components who are direct-commissioned into medicine, law, religion, biological sciences, or healthcare administration. COT is fully integrated into the OTS program and today encompasses extensive coursework as well as field exercises in leadership, confidence, fitness, and deployed-environment operations.
==== Air Force Fitness Test ====
The US Air Force Fitness Test (AFFT) is designed to test the abdominal circumference, muscular strength/endurance and cardiovascular respiratory fitness of airmen in the USAF. As part of the Fit to Fight program, the USAF adopted a more stringent physical fitness assessment; the new fitness program was put into effect on 1 June 2010. The annual ergo-cycle test which the USAF had used for several years had been replaced in 2004. In the AFFT, Airmen are given a score based on performance consisting of four components: waist circumference, the sit-up, the push-up, and a 1.5-mile (2.4 km) run. Airmen can potentially earn a score of 100, with the run counting as 60%, waist circumference as 20%, and both strength tests counting as 10% each. A passing score is 75 points. Effective 1 July 2010, the AFFT is administered by the base Fitness Assessment Cell (FAC), and is required twice a year. Personnel earning a score over 90% may test once a year. Additionally, only meeting the minimum standards on each one of these tests will not get you a passing score of 75%, and failing any one component will result in a failure for the entire test.
== Aircraft inventory ==
The U.S. Air Force has a total force of approximately 5,500 aircraft. Of these, an estimated 4,131 are in active service. Until 1962, the Army and Air Force maintained one system of aircraft naming, while the U.S. Navy maintained a separate system. In 1962, these were unified into a single system heavily reflecting the Army and Air Force method. For more complete information on the workings of this system, refer to United States military aircraft designation systems. The various aircraft of the Air Force include:
=== A – Attack ===
The attack aircraft of the USAF are designed to attack targets on the ground and are often deployed as close air support for, and in proximity to, U.S. ground forces. The proximity to friendly forces require precision strikes from these aircraft that are not always possible with bomber aircraft. Their role is tactical rather than strategic, operating at the front of the battle rather than against targets deeper in the enemy's rear. Current USAF attack aircraft are operated by Air Combat Command, Pacific Air Forces, and Air Force Special Operations Command. On 1 August 2022, USSOCOM selected the Air Tractor-L3Harris AT-802U Sky Warden as a result of the Armed Overwatch program, awarding an indefinite quantity contract (IDIQ) to deliver as many as 75 aircraft.
A-10C Thunderbolt II
A-29 Super Tucano
AC-130J Ghostrider
OA-1K Sky Warden
=== B – Bomber ===
US Air Force bombers are strategic weapons, primarily used for long range strike missions with either conventional or nuclear ordnance. Traditionally used for attacking strategic targets, today many bombers are also used in the tactical mission, such as providing close air support for ground forces and tactical interdiction missions. All Air Force bombers are under Global Strike Command.
The service's B-2A aircraft entered service in the 1990s, its B-1B aircraft in the 1980s and its current B-52H aircraft in the early 1960s. The B-52 Stratofortress airframe design is over 60 years old and the B-52H aircraft currently in the active inventory were all built between 1960 and 1962. The B-52H is scheduled to remain in service for another 30 years, which would keep the airframe in service for nearly 90 years, an unprecedented length of service for any aircraft. The B-21 is projected to replace the B-52 and parts of the B-1B force by the mid-2020s.
B-1B Lancer
B-2A Spirit
B-52H Stratofortress
=== C – Transport ===
Transport aircraft are typically used to deliver troops, weapons and other military equipment by a variety of methods to any area of military operations around the world, usually outside of the commercial flight routes in uncontrolled airspace. The workhorses of the USAF airlift forces are the C-130 Hercules, C-17 Globemaster III, and C-5 Galaxy. The CV-22 is used by the Air Force for special operations. It conducts long-range, special operations missions, and is equipped with extra fuel tanks and terrain-following radar. Some aircraft serve specialized transportation roles such as executive or embassy support (C-12), Antarctic support (LC-130H), and AFSOC support (C-27J and C-146A). Although most of the US Air Force's cargo aircraft were specially designed with the Air Force in mind, some aircraft such as the C-12 Huron (Beechcraft Super King Air) and C-146 (Dornier 328) are militarized conversions of existing civilian aircraft. Transport aircraft are operated by Air Mobility Command, Air Force Special Operations Command, and United States Air Forces in Europe – Air Forces Africa.
C-5M Galaxy
C-12C, C-12D, C-12F and C-12J Huron
C-17A Globemaster III
C-130H, LC-130H, and WC-130H Hercules
C-130J and C-130J-30 Super Hercules
C-146A Wolfhound
CV-22B Osprey
=== E – Special Electronic ===
The purpose of electronic warfare is to deny the opponent an advantage in the EMS and ensure friendly, unimpeded access to the EM spectrum portion of the information environment. Electronic warfare aircraft are used to keep airspaces friendly, and send critical information to anyone who needs it. They are often called "the eye in the sky". The roles of the aircraft vary greatly among the different variants to include electronic warfare and jamming (EC-130H), psychological operations and communications (EC-130J), airborne early warning and control (E-3), airborne command post (E-4B), range control (E-9A), and communications relay (E-11A, EQ-4B).
E-3B, E-3C and E-3G Sentry
E-4B "Nightwatch"
E-9A Widget
E-11A
EC-130H Compass Call
EC-130J Commando Solo
=== F – Fighter ===
The fighter aircraft of the USAF are small, fast, and maneuverable military aircraft primarily used for air-to-air combat. Many of these fighters have secondary ground-attack capabilities, and some are dual-roled as fighter-bombers (e.g., the F-16 Fighting Falcon); the term "fighter" is also sometimes used colloquially for dedicated ground-attack aircraft, such as the F-117 Nighthawk. Other missions include interception of bombers and other fighters, reconnaissance, and patrol. The F-16 is currently used by the USAF Air Demonstration squadron, the Thunderbirds, while a small number of both man-rated and non-man-rated F-4 Phantom II are retained as QF-4 aircraft for use as full-scale aerial targets (FSATs) or as part of the USAF Heritage Flight program. These extant QF-4 aircraft are being replaced in the FSAT role by early model F-16 aircraft converted to QF-16 configuration. The USAF had 2,025 fighters in service as of September 2012.
F-15C and F-15D Eagle
F-15E Strike Eagle
F-15EX Eagle II
F-16C, F-16D Fighting Falcon
F-22A Raptor
F-35A Lightning II
=== H – Search and rescue ===
These aircraft are used for search and rescue and combat search and rescue on land or sea. The HC-130N/P aircraft are being replaced by newer HC-130J models. HH-60W are replacement aircraft for "G" models that have been lost in combat operations or accidents. New HH-60W helicopters are under development to replace both the "G" and "W" model Pave Hawks. The Air Force also has four HH-60U "Ghost Hawks", which are converted "M" variants. They are based out of Area 51.
HC-130N and HC-130P Combat King
HC-130J Combat King II
HH-60G, HH-60U and HH-60W Pave Hawk
=== K – Tanker ===
The USAF's KC-135 and KC-10 aerial refueling aircraft are based on civilian jets. The USAF aircraft are equipped primarily for providing the fuel via a tail-mounted refueling boom, and can be equipped with "probe and drogue" refueling systems. Air-to-air refueling is extensively used in large-scale operations and also used in normal operations; fighters, bombers, and cargo aircraft rely heavily on the lesser-known "tanker" aircraft. This makes these aircraft an essential part of the Air Force's global mobility and the U.S. force projection. The KC-46A Pegasus began to be delivered to USAF units starting in 2019.
KC-10A Extender
KC-46A Pegasus
KC-135R and KC-135T Stratotanker
=== M – Multi-mission ===
Specialized multi-mission aircraft provide support for global special operations missions. These aircraft conduct infiltration, exfiltration, resupply, and refueling for SOF teams from improvised or otherwise short runways. The MC-130J is currently being fielded to replace "H" and "P" models used by U.S. Special Operations Command. The MC-12W is used in the "intelligence, surveillance, and reconnaissance" (ISR) role.
Initial generations of RPAs were primarily surveillance aircraft, but some were fitted with weaponry (such as the MQ-1 Predator, which used AGM-114 Hellfire air-to-ground missiles). An armed RPA is known as an "unmanned combat aerial vehicle" (UCAV).
MC-12W Liberty
MC-130H Combat Talon II
MC-130J Commando II
MQ-9B Reaper
=== R – Reconnaissance ===
The reconnaissance aircraft of the USAF are used for monitoring enemy activity, originally carrying no armament. Although the U-2 is designated as a "utility" aircraft, it is a reconnaissance platform. The roles of the aircraft vary greatly among the different variants to include general monitoring, ballistic missile monitoring (RC-135S), electronic intelligence gathering (RC-135U), signal intelligence gathering (RC-135V/W), and high altitude surveillance (U-2)
Several unmanned remotely controlled reconnaissance aircraft (RPAs), have been developed and deployed. Recently, the RPAs have been seen to offer the possibility of cheaper, more capable fighting machines that can be used without risk to aircrews.
RC-135S Cobra Ball
RC-135U Combat Sent
RC-135V and RC-135W Rivet Joint
RQ-4B Global Hawk
RQ-11 Raven
RQ-170 Sentinel
U-2S "Dragon Lady"
=== T – Trainer ===
The Air Force's trainer aircraft are used to train pilots, combat systems officers, and other aircrew in their duties.
T-1A Jayhawk
T-6A Texan II
T-38A, (A)T-38B and T-38C Talon
T-41D Mescalero
T-51A
T-53A Kadet II
TC-135W
TH-1H Iroquois
TU-2S Dragon Lady
=== TG – Trainer gliders ===
Several gliders are used by the USAF, primarily used for cadet flying training at the U.S. Air Force Academy.
TG-15A
TG-15B
TG-16
=== U – Utility ===
Utility aircraft are used basically for what they are needed for at the time. For example, a Huey may be used to transport personnel around a large base or launch site, while it can also be used for evacuation. These aircraft are all around use aircraft.
U-28A Draco
UH-1N Iroquois
UV-18B Twin Otter
=== V – VIP staff transport ===
These aircraft are used for the transportation of Very Important Persons (VIPs). Notable people include the president, vice president, cabinet secretaries, government officials (e.g., senators and representatives), the Joint Chiefs of Staff, and other key personnel.
VC-25A (two used as Air Force One)
C-21A Learjet
C-32A and C-32B (used as Air Force Two)
C-37A Gulfstream V and C-37B Gulfstream G550
C-40B and C-40C
=== W – Weather reconnaissance ===
These aircraft are used to study meteorological events such as hurricanes and typhoons.
WC-130J Hurricane Hunter
WC-135C and WC-135W Constant Phoenix
=== Undesignated foreign aircraft ===
CN-235-100 (427th Special Operations Squadron)
Grob G 120TP
Mil Mi-17 (OPFOR training)
== See also ==
== Notes ==
== References ==
== External links ==
=== Official ===
Official USAF site
Air Force Blue Tube page on youtube.com
=== Other ===
Searchable database of Air Force historical reports
USAF emblems
USAF Communications Troops
Members of the US Air Force on RallyPoint
Aircraft Investment Plan, Fiscal Years (FY) 2011–2040, Submitted with the FY 2011 Budget
National Commission on the Structure of the Air Force: Report to the President and the Congress of the United States
Works by or about United States Air Force at Internet Archive | The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal Corps, the USAF was established as a separate branch of the United States Armed Forces in 1947 with the enactment of the National Security Act of 1947. It is the second youngest branch of the United States Armed Forces and the fourth in order of precedence. The United States Air Force articulates its core missions as air supremacy, global integrated intelligence, surveillance and reconnaissance, rapid global mobility, global strike, and command and control.
The United States Air Force is a military service branch organized within the Department of the Air Force, one of the three military departments of the Department of Defense. The Air Force through the Department of the Air Force is headed by the civilian Secretary of the Air Force, who reports to the Secretary of Defense and is appointed by the President with Senate confirmation. The highest-ranking military officer in the Air Force is the Chief of Staff of the Air Force, who exercises supervision over Air Force units and serves as one of the Joint Chiefs of Staff. As directed by the Secretary of Defense and Secretary of the Air Force, certain Air Force components are assigned to unified combatant commands. Combatant commanders are delegated operational authority of the forces assigned to them, while the Secretary of the Air Force and the Chief of Staff of the Air Force retain administrative authority over their members.
Along with conducting independent air operations, the United States Air Force provides air support for land and naval forces and aids in the recovery of troops in the field. As of 2020, the service operates approximately 5,500 military aircraft and approximately 400 ICBMs. The world's largest air force, it has a $179.7 billion budget and is the second largest service branch of the U.S. Armed Forces, with 321,848 active duty airmen, 147,879 civilian personnel, 68,927 reserve airmen, 105,104 Air National Guard airmen, and approximately 65,000 Civil Air Patrol auxiliarists. | 11 |
303 | usaf | United States Armed Forces (wikipedia) | The United States Armed Forces are the military forces of the United States. The armed forces consist of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. All six armed services are among the eight uniformed services of the United States, along with the U.S. Public Health Service Commissioned Corps and the NOAA Commissioned Officer Corps.
Each of the different military services is assigned a role and domain. The Army conducts land operations. The Navy and Marine Corps conduct maritime operations, the Marine Corps specializing in amphibious and maritime littoral operations primarily for supporting the Navy. The Air Force conducts air operations. The Space Force conducts space operations. The Coast Guard is unique in that it specializes in maritime operations and is also a law enforcement agency.
From their inception during the American Revolutionary War, the U.S. Armed Forces have played a decisive role in the country's history. They helped forge a sense of national unity and identity through victories in the early-19th-century First and Second Barbary Wars. They played a critical role in the territorial evolution of the U.S., including the American Civil War. The National Security Act of 1947 created the modern U.S. military framework, establishing the National Military Establishment (later the Department of Defense or DoD) headed by the secretary of defense and creating both the U.S. Air Force and National Security Council; in 1949, an amendment to the act merged the cabinet-level departments of the Army, Navy, and Air Force into the DoD.
The president of the U.S. is the commander-in-chief of the armed forces and forms military policy with the DoD and Department of Homeland Security (DHS), both federal executive departments, acting as the principal organs by which military policy is carried out.
The U.S. Armed Forces are one of the world's largest military forces in terms of personnel. They draw their personnel from a large pool of professional volunteers. The U.S. has used military conscription, but not since 1973. The Selective Service System retains the power to conscript males, requiring the registration of all male citizens and residents living in the U.S. between the ages of 18 and 25.
The U.S. Armed Forces are considered the world's most powerful military, especially since the end of the Cold War. The military expenditure of the U.S. was US$916 billion in 2023, the highest in the world, accounting for 37% of the world's defense expenditures. The U.S. Armed Forces has significant capabilities in both defense and power projection due to its large budget, resulting in advanced and powerful technologies which enable widespread deployment of the force around the world, including around 800 military bases outside the U.S. The U.S. Air Force is the world's largest air force, followed by the U.S. Army Aviation Branch. The U.S. Naval Air Forces is the fourth-largest air arm in the world and is the largest naval aviation service, while U.S. Marine Corps Aviation is the world's seventh-largest air arm. The U.S. Navy is the world's largest navy by tonnage. The U.S. Coast Guard is the world's 12th-largest maritime force. The U.S. Space Force is the world's only active independent space force.
== History ==
The history of the U.S. Armed Forces dates back to 14 June 1775, with the creation of the Continental Army, even before the Declaration of Independence marked the establishment of the United States. The Continental Navy, established on 13 October 1775, and Continental Marines, established on 10 November 1775, were created in close succession by the Second Continental Congress in order to defend the new nation against the British Empire in the American Revolutionary War.
These forces demobilized in 1784 after the Treaty of Paris ended the Revolutionary War. The Congress of the Confederation created the current United States Army on 3 June 1784. The United States Congress created the current United States Navy on 27 March 1794 and the current United States Marine Corps on 11 July 1798. All three services trace their origins to their respective Continental predecessors. The 1787 adoption of the Constitution gave Congress the power to "raise and support armies," to "provide and maintain a navy," and to "make rules for the government and regulation of the land and naval forces," as well as the power to declare war. The President of the United States is the U.S. Armed Forces' commander-in-chief.
The United States Coast Guard traces its origin to the formation of the Revenue Cutter Service on 4 August 1790, which merged with the United States Life-Saving Service on 28 January 1915 to establish the Coast Guard. The United States Air Force was established as an independent service on 18 September 1947; it traces its origin to the formation of the Aeronautical Division, U.S. Signal Corps, which was formed 1 August 1907 and was part of the Army Air Forces before being recognized as an independent service in the National Security Act of 1947. The United States Public Health Service Commissioned Corps was formerly considered to be a branch of the United States Armed Forces from 29 July 1945 until 3 July 1952, and is now one of the eight uniformed services of the United States. Should it be called into active duty again, it would constitute a seventh branch of the Armed Forces.
The United States Space Force was established as an independent service on 20 December 2019. It is the sixth branch of the U.S. military and the first new branch in 72 years. The origin of the Space Force can be traced back to the Air Force Space Command, which was formed 1 September 1982 and was a major command of the United States Air Force.
The U.S. Congressional Research Office annually publishes a List of Notable Deployments of U.S. Military Forces Overseas since 1798.
== Structure ==
Presidential command over the U.S. Armed Forces is established in Article II in the Constitution whereby the president is named as the "Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States." The United States Armed Forces are split between two cabinet departments, with the Department of Defense serving as the primary cabinet department for military affairs and the Department of Homeland Security responsible for administering the United States Coast Guard.
The military chain of command flows from the President of the United States to the secretary of defense (for services under the Defense Department) or secretary of homeland security (for services under the Department of Homeland Security), ensuring civilian control of the military. Within the Department of Defense, the military departments (Department of the Army, United States Department of the Navy, and Department of the Air Force) are civilian led entities that oversee the coequal military service branches organized within each department. The military departments and services are responsible for organizing, training, and equipping forces, with the actual chain of command flowing through the unified combatant commands.
The Joint Chiefs of Staff, although outside the operational chain of command, is the senior-most military body in the United States Armed Forces. It is led by the chairman of the Joint Chiefs of Staff, who is the military head of the armed forces and principal advisor to the president and secretary of defense on military matters. Their deputy is the vice chairman of the Joint Chiefs of Staff. Other members include the chief of staff of the Army, commandant of the Marine Corps, chief of naval operations, chief of staff of the Air Force, chief of space operations, and the chief of the National Guard Bureau. The commandant of the Coast Guard is not an official member of the Joint Chiefs, but sometimes attends meetings as one of the military service chiefs. The senior enlisted advisor to the chairman is the most senior enlisted member in the United States Armed Forces.
Leadership of the Armed Forces, to include the president of the United States, the secretary of defense, the secretary of Homeland Security and chairman of the Joint Chiefs of Staff are members of the United States National Security Council, which advises the president on national security, military, and foreign policy matters. The national security advisor, the homeland security advisor, and the deputy national security advisor may also be members of the United States Armed Forces. The National Security Council Deputies Committee also includes the deputy secretary of defense, deputy secretary of homeland security, and vice chairman of the Joint Chiefs of Staff. Military leadership, including the secretary of defense, the secretary of Homeland Security, and chairman of the Joint Chiefs of Staff also sit on the National Space Council.
=== Unified combatant commands ===
Unified combatant commands are joint military commands consisting of forces from multiple military departments, with their chain of command flowing from the president, to the secretary of defense, to the commanders of the combatant commands. Each service organizes, trains, and equips forces that are then presented to the unified combatant commands through service component commands. Special Operations Command and Cyber Command also present theater special operations commands or joint force headquarters – cyber to other combatant commanders. Army components are typically dual-hatted as the joint force land component, Navy components are typically dual-hatted as the joint force maritime component, and Air Force components are typically dual-hatted as the joint force air component, with the theater special operations command dual-hatted as the joint force special operations component, and Space Force component typically dual-hatted as the joint force space component.
=== Combat support agencies ===
Combat support agencies are Department of Defense agencies with combat support missions that service operating forces planning or conducting military operations. This includes support during conflict or in the conduct of other military activities related to countering threats to U.S. national security. This mission is focused on providing support to echelons at the CCMD level and below and may not encompass the full scope of the CSA's mission.
== Service branches ==
The United States Armed Forces is composed of six coequal military service branches. Five of the branches, the United States Army, United States Marine Corps, United States Navy, United States Air Force, and United States Space Force, are organized under the Department of Defense's military departments. The United States Coast Guard is nominally under the Department of Homeland Security, but may be transferred to the Department of Defense's Department of the Navy (which is the civilian entity that oversees the coequal U.S. Marine Corps and U.S. Navy) at the direction of the President or Congress. With the exception of the Coast Guard, the military services only organize, train, and equip forces. The unified combatant commands are responsible for operational control of non-service retained forces.
Each of the different military services is assigned a role and domain. The U.S. Army conducts land operations, while the U.S. Navy and U.S. Marine Corps conduct maritime operations, with the Marine Corps specializing in amphibious and maritime littoral operations in support of the Navy. The U.S. Air Force conducts air operations, while the U.S. Space Force conducts space operations. The U.S. Coast Guard is unique in that it is a military branch specializing in maritime operations and also a law enforcement agency.
=== U.S. Army ===
The United States Army (USA) is the United States Armed Forces' land force and is the largest and oldest service. Originally established in 1775 as the Continental Army, it consists of one million soldiers across the Regular Army, Army Reserve, and Army National Guard. The Army serves as the Armed Forces principal land service, responsible for conducting land warfare operations.
The U.S. Army is organized under the Department of the Army, which is a military department under the leadership of the secretary of the Army and under secretary of the Army. The U.S. Army itself is led by the chief of staff of the Army and vice chief of staff of the Army, both generals who are advised by the sergeant major of the Army.
The Army's primary responsibility is to conduct prompt and sustained land combat as part of the joint force. Army landpower focuses on destroying an enemy's armed forces, occupying its territory, and breaking the will of an adversary.
The five core competencies of the Army are:
Prompt and sustained land combat
Combined arms operations:
Combined arms maneuver and wide area security
Armored and mechanized operations
Airborne and air assault operations
Special operations
Set and sustain the theater for the joint force
Integrate national, multinational, and joint power on land
The thirteen specified functions of the Army are:
Conduct prompt and sustained combined arms combat operations on land in all environments and types of terrain, to include complex urban environments, in order to defeat enemy ground forces, and seize, occupy, and defend land areas.
Conduct air and missile defense to support joint campaigns and assist in achieving air superiority. This is conducted by the Army's Air Defense Artillery Branch, specifically by the 10th Army Air and Missile Defense Command, 32nd Army Air and Missile Defense Command, 94th Army Air and Missile Defense Command, 263rd Army Air and Missile Defense Command, and Army Space and Missile Defense Command.
Conduct airborne and air assault, and amphibious operations. The Army has primary responsibility for the development of airborne doctrine, tactics, techniques, and procedures. Army airborne and air assault operations are conducted by the XVIII Airborne Corps, 11th Airborne Division, 82nd Airborne Division, 101st Airborne Division, and the 173rd Airborne Brigade.
Conduct civil affairs operations. Civil affairs operations are conducted by the United States Army Special Operations Command, predominantly under United States Army Civil Affairs and Psychological Operations Command and the 95th Civil Affairs Brigade.
Conduct riverine operations.
Occupy territories abroad and provide for the initial establishment of a military government pending transfer of this responsibility to other authorities.
Interdict enemy sea power, space power, air power, and communications through operations on and from the land.
Provide logistics to joint operations and campaigns, including joint over-the-shore and intra-theater transport of time-sensitive, mission-critical personnel and materiel. This is primarily conducted through the Army Logistics Branch, including the Quartermaster Corps, Ordnance Corps, Transportation Corps, and through Army Materiel Command's Military Surface Deployment and Distribution Command.
Provide support to space operations to enhance joint campaigns, in coordination with the other military services (primarily the United States Space Force), combatant commands (primarily United States Space Command), and other U.S. government departments and agencies. Army space operations are conducted by Army Space and Missile Defense Command.
Conduct authorized civil works programs, to include projects for the improvement of navigation, flood control, beach erosion control, and other water resource developments in the United States, its territories, and its possessions, and conduct other civil activities prescribed by law. These are conducted by the Army Corps of Engineers.
Provide intra-theater aeromedical evacuation. These missions are flown by the Army Medical Service Corps and Army Aviation Branch.
Conduct reconnaissance, surveillance, and target acquisition.
Operate land lines of communication. This is primarily conducted through the Transportation Corps and Military Surface Deployment and Distribution Command.
==== Infantry ====
The Infantry Branch forms the core of the service's land combat power. U.S. Army infantry are generally equipped with the M4 carbine and M249 light machine gun, which will be replaced by the XM7 rifle and XM250.
Infantry is a core part of the Army's Brigade Combat Teams. The most numerous variant, the Infantry Brigade Combat Team, comprises light infantry battalions who fight on foot. Infantry Brigade Combat Teams of the 82nd Airborne Division are air assault capable, with infantry soldiers being transported by U.S. Army Aviation UH-60 Black Hawk and CH-47 Chinook helicopters. Infantry Brigade Combat Teams of the 11th Airborne Division, 82nd Airborne Division, and 173rd Airborne Brigade are capable of airborne operations, in cooperation with the U.S. Air Force's transport aircraft. Finally, Infantry Brigade Combat Teams assigned to the 10th Mountain Division specialize in mountain warfare. Standard Infantry Brigade Combat Teams are assigned to the 25th Infantry Division, which offers additional training in jungle warfare.
Armored Brigade Combat Teams comprise mechanized infantry battalions mounted in the M2 Bradley infantry fighting vehicle. Divisions with Armored Brigade Combat Teams include the 1st Infantry Division, 3rd Infantry Division, 4th Infantry Division, 1st Armored Division, and 1st Cavalry Division. Stryker Brigade Combat Teams are centered around Stryker infantry battalions operating out of the Stryker. Divisions with Stryker Brigade Combat Teams include the 2nd Infantry Division, 4th Infantry Division, 11th Airborne Division, 2nd Cavalry Regiment, and 3rd Cavalry Regiment.
United States Army Rangers with the 75th Ranger Regiment are an elite special operations infantry force in the United States Army Special Operations Command, specializing in air assault and airborne infiltration methods. The three primary missions of the 75th Ranger Regiment are special operations raids, forcible entry operations, such as an airfield seizure to enable the Air Force to bring in more forces, and special reconnaissance. As a special operations force, Army Rangers are generally better equipped than standard infantry, utilizing the FN SCAR rifle.
==== Army Special Forces ====
Army Special Forces, commonly known as Green Berets after their iconic headgear, are among the most elite soldiers in the Army. Special Forces conduct:
counterinsurgency distinguishing between civilians and enemy combatants while assisting with the stabilization, defense, and training of developing countries facing insurgent threats.
direct action seizing, capturing, recovering, or destroying enemy material; or utilizing quick strikes to recover personnel.
foreign internal defense training and equipping foreign allied military forces to defend against insurgency, subversion, terrorism, and other security threats.
special reconnaissance executing surveillance in hostile, denied, or diplomatically- or politically-sensitive environments to collect or verify information of strategic significance.
unconventional warfare enabling a resistance movement or insurgency to coerce, disrupt, or overthrow a government or occupying power by operating through or with an underground force in a denied area.
Army Special Forces are trained in military free-fall parachuting and combat diver skillsets. They are considered the most versatile special operations force in the entire world, operating as a multi-purpose force since 1952.
==== Armor and Cavalry ====
The Armor Branch traces its history back to the United States Cavalry and are responsible for tank and cavalry reconnaissance operations.
The U.S. Army fields the M1 Abrams main battle tank in Armored Battalions as part of Armored Brigade Combat Teams across the 1st Armored Division, 1st Cavalry Division, 1st Infantry Division, 3rd Infantry Division, and the 4th Infantry Division. Each Armored Brigade Combat Team also possesses a cavalry squadron equipped with M2 Bradleys for scouting and security. Stryker Brigade Combat Teams from the 2nd Infantry Division, 4th Infantry Division, 11th Airborne Division, 2nd Cavalry Regiment, and 3rd Cavalry Regiment have a cavalry squadron equipped with Strykers. Infantry Brigade Combat Teams from the 10th Mountain Division, 11th Airborne Division, 25th Infantry Division, 82nd Airborne Division, 101st Airborne Division, and 173rd Airborne Brigade have a cavalry squadron equipped with the Joint Light Tactical Vehicle.
==== Field Artillery ====
The Field Artillery's mission is to destroy, suppress or neutralize the enemy by cannon, rocket or missile fire. Rocket systems include the M142 HIMARS and M270 Multiple Launch Rocket System, which are corps-level assets found in field artillery brigades. Towed artillery includes the M119 howitzer in Infantry Brigade Combat Teams and the M777 howitzer found in both Infantry and Stryker Brigade Combat Teams. The M109 self-propelled howitzer is utilized in Armored Brigade Combat Teams.
During the Cold War, Army field artillery was responsible for the service's ballistic missile programs, including the PGM-11 Redstone, which was the first large ballistic missile in the U.S. arsenal, the MGM-31 Pershing, and the Pershing II. In 2023, the Army is intending to field the Long-Range Hypersonic Weapon and has reestablished larger artillery formations like the 56th Artillery Command.
==== Air Defense Artillery ====
The Air Defense Artillery is responsible for defending geopolitical assets and providing maneuver forces with the freedom to move on the battlefield by deterring the enemy and destroying aerial threats, missile attacks, and surveillance platforms. Weapons employed by Air Defense Artillery include the FIM-92 Stinger man-portable air-defense system, AN/TWQ-1 Avenger for short range air defense, and the counter rocket, artillery, and mortar 20mm gun system. The Iron Dome provides air defense against rockets, artillery, mortars, missiles, and unmanned aerial vehicles. The MIM-104 Patriot is capable of defeating a wide range of threats including aircraft, helicopters, UAVs, ballistic and cruise missiles, and Weapons of Mass Destruction.
The Terminal High Altitude Area Defense protects strategic critical assets by conducting long-range endo-and-exo-atmospheric engagements of ballistic missiles using the world's largest air-transportable X-band radar. The Ground-Based Midcourse Defense is an anti-ballistic missile system operated by Army Space and Missile Defense Command to defend the United States homeland against an intercontinental ballistic missile attack. Major Air Defense Artillery units include the 32nd Army Air and Missile Defense Command and Army Space and Missile Defense Command's 100th Missile Defense Brigade.
Air Defense Artillery has an extremely close relationship with the Air Force through its Air and Missile Defense Commands and the Space Force through Army Space and Missile Defense Command, given their shared missile defense and space roles. In 1962, Air Defense Artillery achieved the first intercept of a ballistic missile with a nuclear-tipped Nike Zeus and operated the Nike Zeus as an anti-satellite weapon after completing a successful intercept in 1963.
==== Army Aviation ====
Army Aviation, distinct from the U.S. Air Force and its predecessors, began as part of the field artillery in 1942. Small spotter planes were used to spot for artillery and naval bombardment, as well as to perform observation. These few aircraft formed the core of Army Aviation once the U.S. Air Force gained independence. In 1983, the Army created the Aviation Branch, for the first time since the Air Force's independence consolidating aviation under a single organization.
The mission of Army Aviation is to find, fix and destroy any enemy through fire and maneuver and to provide combat support and combat service support in coordinated operations as an integral member of the combined arms team. Major aircraft include the AH-64 Apache, which serves as the Army's attack helicopter, the UH-60 Black Hawk, and the CH-47 Chinook for troop and cargo transport. Army Aviation also flies the MQ-1C Gray Eagle drone.
A specialized unit within Army Aviation, the 160th Special Operations Aviation Regiment (Airborne) serves as a special operations unit and operates modified variants of the MH-60 Black Hawk, MH-47 Chinook, and the MH-6 Little Bird.
==== Army commands ====
The U.S. Army is organized into four major Army Commands, nine Army Service Component Commands which serve as the Army component and joint force land component commanders for the unified combatant commands, and thirteen direct reporting units.
=== U.S. Marine Corps ===
The United States Marine Corps (USMC) serves as the U.S. Armed Forces' naval land force, responsible for executing amphibious warfare and operating in the maritime littorals in support of the U.S. Navy. Originally established in 1775 as the Continental Marines, the Marine Corps consists of the Regular Marine Corps and the Marine Corps Reserve. The Marine Corps maintains a very close relationship with the U.S. Navy, its sister service in the Department of the Navy. Although the Marine Corps has previously operated as an independent land force alongside the Army, its primary purpose is to serve as part of a unified naval service alongside the Navy in the maritime domain.
The U.S. Marine Corps is organized under the Department of the Navy, which is a military department under the leadership of the secretary of the Navy and the under secretary of the Navy. The U.S. Marine Corps itself is led by the commandant of the Marine Corps and the assistant commandant of the Marine Corps, both generals who are advised by the sergeant major of the Marine Corps.
The Marine Corps statutory mission is outlined in 10 U.S.C. § 5063 and as originally introduced under the National Security Act of 1947, with its three primary areas of responsibility including:
Seizure or defense of advanced naval bases and other land operations to support naval campaigns;
Development of tactics, technique, and equipment used by amphibious landing forces in coordination with the Army and Air Force; and
Such other duties as the President or Department of Defense may direct.
The seven specified functions of the Marine Corps are:
Seize and defend advanced naval bases or lodgments to facilitate subsequent joint operations.
Provide close air support for ground forces.
Conduct land and air operations essential to the prosecution of a naval campaign or as directed.
Conduct complex expeditionary operations in the urban littorals and other challenging environments.
Conduct amphibious operations, including engagement, crisis response, and power projection operations to assure access. The Marine Corps has primary responsibility for the development of amphibious doctrine, tactics, techniques, and equipment.
Conduct security and stability operations and assist with the initial establishment of a military government pending transfer of responsibility to other authorities.
Provide security detachments and units for service on armed vessels of the Navy, provide protection of naval property at naval stations and bases, provide security at designated U.S. embassies and consulates, and perform other such duties as the president or secretary of defense may direct. These additional duties may not detract from or interfere with the operations for which the Marine Corps is primarily organized.
Marine Corps Security Force Regiment is responsible for supporting the Navy with Marine security operations, while the Marine Security Guard protects embassies and consulates of the United States Department of State.
==== Fleet Marine Force ====
The combat power of the Marine Corps is centralized in the Fleet Marine Force (FMF), which itself is organized into Fleet Marine Force Atlantic, to support the U.S. Navy's Fleet Forces Command, and Fleet Marine Force Pacific, which supports the U.S. Navy's U.S. Pacific Fleet.
The basic Marine Corps unit for conducting operations is the Marine Air-Ground Task Force (MAGTF), which combines Marine Corps and Navy land, air, sea, and cyberspace capabilities into a single command. There are three size variants of a Marine Air-Ground Task Force, but each consists of a command element, ground combat element, aviation combat element, and logistics combat element.
A Marine ground combat element (GCE) is centered around Marine infantry, typically armed with a M27 Infantry Automatic Rifle. Unlike the Army, the Marine Corps does not train its own combat medics, relying on the Navy to provide hospital corpsmen. These infantry units are supported by Marine Corps combat engineers, who conduct engineer reconnaissance, obstacle system emplacement, and breaching operations; and Marine Corps Force Reconnaissance teams. While the Marine Corps no longer operates its own tanks, opting to request support from the Army if needed, it maintains Light Armored Reconnaissance Battalions which operate the LAV-25 amphibious armored reconnaissance vehicle. Assault Amphibian Battalions operate the Assault Amphibious Vehicle and Amphibious Combat Vehicle, which enable the ground combat element to conduct amphibious landing operations. Marine Corps artillery operates the M777 howitzer and the M142 HIMARS, both supporting the ground combat element and the Navy at sea by striking enemy ships.
The Marine aviation combat element (ACE) is the operational arm of Marine Corps Aviation, working to support the ground combat element. The F-35B Lightning II and AV-8B Harrier II are flown off Navy amphibious assault ships, while the F-35C Lightning II and F/A-18 Hornet are flown off Navy carriers by Marine Corps pilots. The Marine Corps also operates the KC-130J to serve as a tanker and tactical airlift platform. The UH-1Y Venom helicopter provides the Marine Corps with light transport and attack, while the AH-1Z Viper is a dedicated attack helicopter. Medium-lift squadrons fly the MV-22 Osprey, while heavy-lift squadrons use the CH-53K King Stallion. The Marine Corps has also begun flying unmanned aerial vehicles, such as the MQ-9 Reaper and MQ-8 Fire Scout. Notably, the aviation combat element also includes Low-Altitude Air Defense Battalions, which employ the FIM-92 Stinger surface-to-air missile.
The smallest MAGTF is the Marine Expeditionary Unit (MEU), which is typically forward deployed on a Navy ship. Commanded by a colonel, a Marine Expeditionary Unit consist of 2,200 marines split across a battalion landing team (ground combat element), a composite helicopter squadron (aviation combat element), and a combat logistics element (logistics element). Marine Expeditionary Units are supplied for 15 days. Forward deployed Marine Expeditionary Units are often embarked on Navy amphibious assault ships as part of an amphibious ready group.
The mid-sized MAGTF is the Marine Expeditionary Brigade (MEB), which is organized for specific missions. Commanded by a brigadier general, Marine Expeditionary Brigades consist of 4,000 to 16,000 marines across a Regimental-sized ground combat element, a Marine Aircraft Group, and a Combat Logistics Regiment. Marine Expeditionary Brigades are supplied for 30 days and offer increased firepower and airpower over the Marine Expeditionary Unit.
The largest MAGTF is the Marine Expeditionary Force (MEF), which is the primary warfighting force for larger operations. A Marine Expeditionary Force is commanded by a lieutenant general and consists of 46,000 to 90,000 marines. Currently there are only three Marine Expeditionary Forces, each with its own Marine Division, Marine Aircraft Wing, Marine Logistics Group, and Marine Expeditionary Force Information Group. Marine Expeditionary Forces are supplied for 60 days. Certain elements are held at the Marine Expeditionary Force level, such as Force Reconnaissance. The MEF Information Group (MIG) also provides a number of functions such as the intelligence battalion; radio battalion which conducts signals intelligence, electronic warfare, and cyberspace operations; communications battalion; the MEF support battalion; and the Air Naval Gunfire Liaison Company.
While not a MAGTF, the Marine Corps has begun to reorganize some of its regiments into Marine Littoral Regiments (MRL), which are similar in size to a Marine Expeditionary Unit. A Marine Littoral Regiment is a self-deployable force, designed to be naval in nature and operate in the littoral region. A Marine Littoral Regiment consists of a littoral combat team, a littoral anti-air battalion, and a combat logistics battalion. Notably, the Marine Littoral Regiment has no aviation combat element, unlike a Marine Expeditionary Unit.
Another Marine Corps element that does not function as part of the MAGTF is the Marine Raider Regiment, functioning under United States Marine Forces Special Operations Command. Marine Raiders specialize in direct action, unconventional warfare, maritime interdiction, special reconnaissance, foreign internal defense, counterterrorism, and counterinsurgency missions.
==== Marine Corps commands ====
Under Headquarters Marine Corps, the Marine Corps is organized into the Fleet Marine Force, multiple commands, and Marine Corps service components to the unified combatant commands.
=== U.S. Navy ===
The United States Navy (USN) is the United States Armed Forces' maritime force. Originally established in 1775 as the Continental Navy, the U.S. Navy consists of the Regular Navy and the Navy Reserve. The Navy is the United States' principal maritime service, responsible for maritime warfare operations.
The U.S. Navy is organized under the Department of the Navy, which is a military department under the leadership of the secretary of the Navy and the under secretary of the Navy. The U.S. Navy itself is led by the chief of naval operations and the vice chief of naval operations, both admirals who are advised by the master chief petty officer of the Navy.
The five enduring functions of the Navy are:
Sea control
Power projection
Deterrence
Maritime security
Sealift
The nine specified tasks of the Navy are:
Conduct offensive and defensive operations associated with the maritime domain including achieving and maintaining sea control, to include subsurface, surface, land, air, space, and cyberspace.
Provide power projection through sea-based global strike, to include nuclear and conventional capabilities; interdiction and interception capabilities; maritime and littoral fires, to include naval surface fires; and close air support for ground forces.
Conduct ballistic missile defense. This is executed through the Navy's Aegis Ballistic Missile Defense System.
Conduct ocean, hydro, and river survey and reconstruction.
Conduct riverine operations. This is conducted by the Maritime Expeditionary Security Force and Naval Special Warfare Command.
Establish, maintain, and defend sea bases in support of naval, amphibious, land, air, or other joint operations as directed.
Provide naval expeditionary logistics to enhance the deployment, sustainment, and redeployment of naval forces and other forces operating within the maritime domain, to include joint sea bases, and provide sea transport for the Armed Forces other than which is organic to the individual military services, United States Special Operations Command, and United States Cyber Command. This is conducted by the Navy Expeditionary Logistics Support Group and Military Sealift Command.
Provide support for joint space operations to enhance naval operations, in coordination with the other military services (primarily the United States Space Force), combatant commands (primarily United States Space Command), and other U.S. government departments and agencies. U.S. Navy space operations are conducted by Navy Space Command.
Conduct nuclear operations in support of strategic deterrence, to include providing and maintaining nuclear surety and capabilities.
==== Naval Surface Forces ====
The Naval Surface Forces (NAVSURFOR) is the backbone of the U.S. Navy's combat power, conducting surface warfare operations and operating its fleet of combat surface ships.
The Naval Surface Forces operates eleven nuclear-powered aircraft carriers (CVN), split between the Nimitz-class and the newer Gerald R. Ford-class. Aircraft carriers are the centerpiece of the U.S. Navy's combat power, forming the nucleus of its eleven carrier strike groups (CSG). Each aircraft carrier has an embarked carrier air wing from the Naval Air Forces.
The Naval Surface Forces also operate 116 surface combatants. These include the Ticonderoga-class guided-missile cruisers, Arleigh Burke-class guided-missile destroyers (DDG) and Zumwalt-class stealth guided-missile destroyers. Cruisers and destroyers often operate as part of larger formations, where they serve as escorts for anti-aircraft and anti-submarine operations. However, they also are able to conduct sea control and striker operations ashore with their tomahawk cruise missiles. The Navy also operates a complement of smaller Freedom-class and Independence-class littoral combat ships (LCS) that can be modularly reconfigured for specific mission sets. Having lacked a frigate since the Oliver Hazard Perry-class was decommissioned, the Navy is in the process of acquiring the new Constellation-class guided-missile frigates (FFG).
Finally, the Naval Surface Forces operate 31 amphibious warfare ships to support the Fleet Marine Force and its embarked Marine Air-Ground Task Forces as part of an amphibious ready group or expeditionary strike group. This includes the America-class landing helicopter assault (LHA) ships which can carry U.S. Marine Corps F-35B Lightning II fighters and helicopters; and Wasp-class landing helicopter dock (LHD) ships, which can carry both F-35B fighters, helicopters, and landing craft. These are in addition to the San Antonio-class amphibious transport docks (LPD), and the Whidbey Island-class and Harpers Ferry-class dock landing ships.
==== Naval Submarine Forces ====
The Naval Submarine Forces (NAVSUBFOR) is often referred to as the "silent service", consisting of 68 commissioned submarines.
Los Angeles-class, Seawolf-class, and Virginia-class nuclear-powered attack submarines are capable of performing sea control missions by destroying enemy submarines and surface ships, conducting surveillance and reconnaissance, performing irregular warfare, covert troop insertion, mine and anti-mine operations, and land attack missions with tomahawk cruise missiles.
Ohio-class nuclear-powered ballistic missile submarines (SSBN) have the sole mission of being launch platforms for the nuclear submarine-launched ballistic missile (SLBM). Each carries 20 UGM-133 Trident II SLBMs. The Navy is currently in the process of procuring the Columbia-class SSBNs to replace the Ohio-class. Some Ohio-class submarines have been converted to cruise-missile submarines (SSGN), capable of carrying 154 tomahawk cruise missiles and deploying 66 special operations forces personnel, such as Navy SEALs.
==== Naval Air Forces ====
The Naval Air Forces (NAVAIRFOR) is the Navy's naval aviation arm, centered around the carrier air wing. The core of the carrier air wing are the Naval Air Forces strike fighter squadrons (VFA), which fly the F-35C Lightning II stealth fighter and the F/A-18E/F Super Hornet. A variant of the F/A-18, the EA-18G Growler is an electronic-warfare aircraft flown by electronic attack squadrons (VAQ) off of carriers or land bases. The E-2 Hawkeye provides carriers with airborne early warning and command-and-control, while the C-2A Greyhound keeps carriers supplied. The CMV-22B Osprey is currently in the process of replacing the C-2 Greyhound for carrier resupply.
The Naval Air Forces also operate the MH-60 Seahawk for anti-submarine warfare, anti-ship warfare, and search and rescue operations. The MH-53E is primarily used for anti-mine warfare but can also be used for assault support.
Although primarily centered on carriers, the Naval Air Forces do operate a small number of land-based aircraft. These include the P-3C Orion and P-8A Poseidon, which conduct anti-submarine warfare operations and serve as maritime patrol aircraft, alongside the unmanned MQ-4C Triton. The E-6 Mercury is also flown by the Navy to communicate instructions to U.S. strategic forces.
==== Navy commands ====
The U.S. Navy is organized into eight navy component commands, which command operational forces and serve as joint force maritime component commands; fifteen shore commands, which support the fleets' operating forces; five systems commands, which oversee the technical requirements of the Navy; and nine type commands, which administratively manage units of a certain type.
=== U.S. Air Force ===
The United States Air Force (USAF) is the United States Armed Forces' air force. Originally established in 1947 when it gained independence from the U.S. Army, it traces its history back through the United States Army Air Forces, United States Army Air Corps, United States Army Air Service, the Division of Military Aeronautics, Aviation Section, U.S. Signal Corps, to the birth of Aeronautical Division, U.S. Signal Corps on 1 August 1907. The U.S. Air Force serves as the principal air service, responsible for aerial warfare operations. The U.S. Air Force is composed of the Regular Air Force, Air Force Reserve, and Air National Guard.
The U.S. Air Force is organized under the Department of the Air Force, which is a military department under the leadership of the secretary of the Air Force and under secretary of the Air Force. The U.S. Air Force itself is led by the chief of staff of the Air Force and vice chief of staff of the Air Force, both generals who are advised by the chief master sergeant of the Air Force.
The five core missions of the Air Force are:
Air superiority
Global integrated intelligence, surveillance, and reconnaissance
Rapid global mobility
Global strike
Command and control
The eight specified functions of the Air Force are:
Conduct nuclear operations in support of strategic deterrence, to include providing and maintaining nuclear surety and capabilities.
Conduct offensive and defensive operations, to include appropriate air and missile defense, to gain and maintain air superiority and air supremacy as required, to enable the conduct of operations by U.S. and allied land, sea, air, space, and special operations forces.
Conduct global precision attack, to include strategic attack, interdiction, close air support, and prompt global strike.
Provide timely, globally integrated intelligence, surveillance, and reconnaissance capability and capacity from forward deployed locations and globally distributed centers to support world-wide operations.
Provide rapid global mobility to employ and sustain organic air and space forces and other military service and U. S. Special Operations Command forces, as directed, to include airlift forces for airborne operations, air logistical support, tanker forces for in-flight refueling, and assets for aeromedical evacuation.
Provide agile combat support to enhance the air and space campaign and the deployment, employment, sustainment, and redeployment of air and space forces and other forces operating within the air and space domains, to include joint air and space bases, and for the Armed Forces other than which is organic to the individual military services and U.S. Special Operations Command in coordination with the other military services, combatant commands, and U.S. Government departments and agencies.
Conduct global personnel recovery operations including theater-wide combat and civil search and rescue in coordination with the other military services, combatant commands, and DoD components.
Conduct globally integrated command and control for air and space operations.
==== Combat Air Force ====
The Combat Air Force (CAF) comprises the majority of the Air Force's combat power, consisting of its fighter, bomber, intercontinental ballistic missile, and special operations forces.
The Air Force's fighter forces are led by Air Combat Command's Fifteenth Air Force, with other fighter units under Pacific Air Forces and United States Air Forces in Europe. Air Force fighters are predominantly used to achieve air superiority and strike enemy ground and naval forces. The Air Force operates an expanding force of fifth-generation fighters. The F-22A Raptor stealth fighter is designed to replace the F-15C in air superiority operations carrying two AIM-9 Sidewinder and six AIM-120 AMRAAM missiles. It also has a significant air-to-ground mission, carrying two GBU-32 Joint Direct Attack Munition bombs, in addition to two AIM-9 and two AIM-120 missiles. Ultimately, the F-22 is intended to be replaced by the sixth-generation fighter, Next Generation Air Dominance program. The F-22 is complemented by the more numerous F-35A Lightning II multi-role stealth fighters, which are in the process of replacing the F-16C fighters and A-10 attack aircraft in air superiority and ground attack roles, to include the nuclear strike mission.
The Air Force still operates an extremely sizable force of fourth-generation fighters. The F-15C Eagle is a dedicated air superiority fighter, while the F-15E Strike Eagle has been modified to be a dual-role strike fighter, carrying both conventional and nuclear weapons. The F-15C Eagle and F-15E Strike Eagle are both being replaced by the F-15EX Eagle II, which is significantly more advanced. The F-16C Fighting Falcon is a multirole fighter that has served as the primary Air Force fighter for decades, including as a dual-capable tactical nuclear strike fighter. The A-10C Thunderbolt II attack aircraft has been the first Air Force fighter specifically designed for close air support missions, operating against enemy ground forces and light naval ships with its GAU-8 Avenger gatling cannon and array of air-to-ground munitions.
The Air Force's bomber forces are organized under Air Force Global Strike Command's Eighth Air Force, executing long-range strike operations. The B-2A Spirit stealth bomber is capable of conducting both conventional and nuclear strike operations flying through air defenses. The B-1B Lancer, in contrast, is a supersonic bomber that carries only conventional munitions and serves as the backbone of the bomber force. Both the B-2A Spirit and the B-1B Lancer are being replaced by the B-21 Raider stealth bomber, which can be equipped with both conventional and nuclear munitions. The B-52H Stratofortress is a long-range, heavy bomber that the Air Force has flown since the 1950s and operates a variety of conventional and nuclear munitions, including the AGM-86 air-launched cruise missile.
The Air Force's intercontinental ballistic missile forces are organized under Air Force Global Strike Command's Twentieth Air Force, serving as the land component of the nuclear triad. The LGM-30G Minuteman III serves as the only ballistic missile operated by the Air Force, with 400 stationed in hardened silos. The LGM-30G will be replaced by the LGM-35A Sentinel intercontinental ballistic missile.
The Air Force's special operations forces are organized under Air Force Special Operations Command, consisting of both special operations aviation and Air Force special tactics airmen on the ground. The AC-130J Ghostrider gunships have the primary mission of close air support and air interdiction, using cannons and precision guided munitions. The MC-130J Commando II, also a variant of the C-130 Hercules, fly exfiltration and resupply operations for special operations forces, along with conducting air-to-air refueling for helicopters. The CV-22 Osprey is a tiltrotor aircraft used for the infiltration and exfiltration of special operations forces. While not under Air Force Special Operations Command, rescue operations are supported by the HC-130J Combat King II and HH-60W Jolly Green II combat rescue aircraft. The MQ-9 Reaper also serves as a remotely piloted intelligence and strike aircraft, serving under Air Force Special Operations Command and Air Combat Command.
Air Force Special Tactics are the ground special warfare force of the U.S. Air Force, integrating air-ground operations. Special Tactics conduct four core missions. Global access teams assess and open airfields, ranging from international airports to dirt strips, in permissive or hostile locations to facilitate the landing and operation of air forces. Precision strike teams are trained to direct aircraft and other forces to conduct kinetic and non-kinetic strikes, as well as humanitarian aid drops. Special Tactics teams also conduct personnel recovery missions, possessing significant medical and rescue experience. Finally, Special Operations Surgical Teams conduct surgery and medical operations in battlefield operations in support of special operations.
The Air Force also operates a wide array of reconnaissance aircraft under Air Combat Command's Sixteenth Air Force, including the RQ-4 Global Hawk drone, U-2 Dragon Lady, and RC-135 Rivet Joint. Air Force operations are typically supported by command and control aircraft, such as the E-3 Sentry airborne warning and control system. The E-3 Sentry is in the process of being replaced by the E-7A Wedgetail.
==== Mobility Air Force ====
The Mobility Air Force (MAF) is organized under Air Mobility Command and comprises the Air Force's airlift, air refueling, and aeromedical evacuation forces.
The airlift forces operate three different major aircraft. The C-5M Super Galaxy is the largest aircraft in the Air Force, serving as a strategic transport aircraft. The C-17A Globemaster III is the airlift force's most flexible aircraft, conducting both strategic and tactical airlift operations. It is also capable of conducting airborne operations for the Army and aerial resupply through airdropping cargo. Finally, the C-130J Super Hercules is a tactical airlifter, conducting both cargo airlift and supporting Army airborne operations. Other major airlift platforms include the VC-25, which serves as the personal plane of the president of the United States, better known as Air Force One.
The Air Force also operates three major aerial refueling tankers. The KC-46A Pegasus is its most modern tanker, replacing the aging KC-10A Extenders. The remaining tanker is the KC-135 Stratotanker, which has flown since the 1950s. Tankers are also capable of conducting limited airlift operations.
==== Air Force commands ====
The U.S. Air Force is organized into nine major commands, which conduct the majority of the service's organize, train, and equip functions. It commands forces attached to the combatant commands as joint force air component commands.
=== U.S. Space Force ===
The United States Space Force (USSF) is the United States Armed Forces' space force and is the newest military branch. Originally established in 2019, it traces its history through Air Force Space Command and the Western Development Division to 1954. The United States Space Force is the principal space service, responsible for space warfare operations. The U.S. Space Force is composed of the Regular Space Force, not yet having organized a reserve component outside of the Air Force.
The U.S. Space Force is organized under the Department of the Air Force, which is a military department under the leadership of the secretary of the Air Force and under secretary of the Air Force. The U.S. Space Force itself is led by the chief of space operations and vice chief of space operations, both generals who are advised by the chief master sergeant of the Space Force.
The five core competencies of the Space Force are:
Space security
Combat power projection
Space mobility and logistics
Information mobility
Space domain awareness
The five specified functions of the Space Force are:
Provide freedom of operation for the United States in, from, and to space.
Provide prompt and sustained space operations.
Protect the interests of the United States in space.
Deter aggression in, from, and to space.
Conduct space operations.
==== Orbital warfare and space electromagnetic warfare ====
The Space Force's combat power is centered around Space Delta 3, which conducts space electromagnetic warfare and Space Delta 9, which conducts orbital warfare.
Combat power projection operations ensure freedom of action in space for the U.S. and its allies and denies an adversary freedom of action in space. These are divided into offensive and defensive space operations. Defensive operations preserve and protect U.S. and allied space capabilities, which are further sub-divided into active and passive actions. Offensive operations target a U.S. adversary's space and counterspace capabilities, achieving space superiority.
Orbital warfare forces conduct protect-and-defend operations and provide U.S. national decision authorities with response options to deter and, when necessary, defeat orbital threats. The space electromagnetic warfare forces conduct offensive and defensive space control operations. Space Force cyber forces conduct defensive cyber operations to protect space assets.
==== Cyber operations and Satellite Control Network ====
Although the U.S. Space Force is not a cyber force, it does conduct extensive cyber operations under Space Delta 6. The primary focus of Space Force cyber operations is defending U.S. Space Force networks and ensuring the operations of its spacecraft, which are controlled remotely from ground stations. All space operations units have cyber squadrons assigned to defend them and incorporate offensive cyber operations.
Additionally, Space Delta 6 is responsible for managing the Satellite Control Network, a global network of antennas used to communicate with the service's spacecraft. The 22nd Space Operations Squadron is responsible for overall operations, with the 21st Space Operations Squadron and 23rd Space Operations Squadron managing the ground station sites at Vandenberg Space Force Base, New Boston Space Force Station, Kaena Point Space Force Station, Diego Garcia, Guam, Greenland, and the United Kingdom.
==== Space domain awareness ====
The Space Force's Space Delta 2 operates the United States Space Surveillance Network, tracking 47,000 objects in space as of 2022. Space domain awareness encompasses the identification, characterization, and understanding of any factor associated with the space domain that could affect space operations.
Space Delta 2 sensors include the AN/FPS-85 phased array radar at Eglin Air Force Base and the Space Fence radar at Kwajalein Atoll operated by the 20th Space Surveillance Squadron; and a global network of three Ground-based Electro-Optical Deep Space Surveillance telescopes operated by the 15th Space Surveillance Squadron.
The 18th Space Defense Squadron, collocated with the Combined Space Operations Center, executes command and control of the Space Surveillance Network and manages the Space Catalog of all objects in Earth orbit. The 19th Space Defense Squadron focuses on objects further in cislunar space, beyond geosynchronous orbit, with a specific focus on supporting NASA's Artemis program and other human spaceflight operations.
==== Missile warning ====
The Space Force's Space Delta 4 uses orbital spacecraft and ground-based radars to conduct theater and strategic missile warnings for the United States and its international partners. This includes the network of Upgraded Early Warning Radars at Beale Air Force Base, Clear Space Force Station, Cape Cod Space Force Station, Pituffik Space Base, and RAF Fylingdales, along with the AN/FPQ-16 PARCS radar at Cavalier Space Force Station. Currently, the Space Force is working with the Missile Defense Agency to acquire the Long Range Discrimination Radar at Clear Space Force Station in Alaska. These ground-based radars also contribute to the Space Surveillance Network.
Space-based missile warning systems include the Defense Support Program and Space-Based Infrared System (SIBRS) spacecraft, which use infrared sensors to conduct missile defense and missile warning. SIBRS also has a battlespace awareness and technical intelligence mission. The Defense Support Program spacecraft are also capable of detecting nuclear detonations, in addition to space and missile launches.
==== Global Positioning System and military satellite communications ====
The Space Force's Space Delta 8 is the operator of the Global Positioning System and the military's array of communications spacecraft.
The Global Positioning System is operated by the 2nd Space Operations Squadron, providing positioning, navigation, and timing information for civilian and military users across the entire world. The Space Force's GPS system has become an integral element of the global information infrastructure, being used in virtually all sectors of the economy, including agriculture, aviation, marine transportation, surveying and mapping, and transit navigation. Its timing signal is used to synchronize global communication systems, electrical power grids, and financial networks. The Global Positioning System also has a secondary mission of carrying nuclear detonation detection sensors.
Military satellite communication systems include the Fleet Satellite Communications System, UHF Follow-On satellite, and Mobile User Objective System, operated by the 10th Space Operations Squadron and inherited from the U.S. Navy. The payloads on the Wideband Global SATCOM and Defense Satellite Communications System are operated by the 53rd Space Operations Squadron, a role inherited from the U.S. Army. Finally, spacecraft operations for the Wideband Global SATCOM and Defense Satellite Communications System are conducted by the 4th Space Operations Squadron, in addition to the Milstar and Advanced Extremely High Frequency satellites, which both additionally support command and control of strategic nuclear forces.
==== Space launch ====
The Space Force's space launch enterprise is organized under Space Systems Command, with Space Launch Delta 30 managing the Western Range from Vandenberg Space Force Base and Space Launch Delta 45 managing the Eastern Range from Cape Canaveral Space Force Station.
The Space Force does not just manage military space launches, but also supports NASA and commercial space launches. Major space launch vehicles flown or scheduled to fly off of Space Force launch ranges include NASA's Space Launch System, SpaceX's Starship, Falcon Heavy, and Falcon 9, and United Launch Alliance's Vulcan, which will replace the Atlas V and Delta IV Heavy. Currently, vehicles for the National Security Space Launch program include the Vulcan, Atlas V, Falcon Heavy, and Falcon 9 rockets.
An experimental Air Force Research Laboratory vanguard program that the Space Force leads, Rocket Cargo, is exploring using rockets to supplement naval and air transport to rapidly deliver supplies to forces across the Earth. The SpaceX Starship rocket is one such system currently being explored.
==== Space Force commands ====
The Space Force is organized into three field commands and multiple component field commands, which serve as joint force space component commands for the unified combatant commands.
=== U.S. Coast Guard ===
The United States Coast Guard (USCG) is the United States Armed Forces' maritime security, maritime search and rescue, and maritime law enforcement force. It was first established in 1790 as the United States Revenue-Marine and consists of the Regular Coast Guard and the Coast Guard Reserve.
Although it has always been one of the six military branches, the Coast Guard is organized under the Department of Homeland Security under the leadership of the secretary of Homeland Security and the deputy secretary of Homeland Security. During times of war, the U.S. Coast Guard can be transferred to the Department of the Navy The Coast Guard itself is led by the commandant of the Coast Guard and vice commandant of the Coast Guard, both admirals advised by the master chief petty officer of the Coast Guard.
The Coast Guard has six major operational mission programs, through which it executes its 11 statutory missions:
Maritime law enforcement
Maritime response
Maritime prevention
Maritime transport system management
Maritime security operations
Defense operations
Maritime law enforcement operations focus on protecting the United States maritime borders and assuring its maritime sovereignty. The Coast Guard conducts operations to suppress violations of U.S. law at sea, including counter-illegal migration and transnational organized crime operations. Codified missions executed under the maritime law enforcement program include drug interdiction, migrant interdiction, living marine resources, and other law enforcement.
Maritime response operations see the Coast Guard conducting search-and-rescue operations and rescuing mariners responding to maritime disasters. Codified missions include search and rescue and marine environmental protection (response activities).
Maritime prevention operations prevent marine casualties and property losses, minimize security risks, and protect the marine environment. The Coast Guard does so by developing and enforcing federal regulations, conducting safety and security inspections, and analyzing port security risk assessments. Codified missions include ports, waterways, and coastal security, marine safety, and marine environmental protection (protection activities).
Maritime transport system management ensures a safe, secure, and environmentally sound waterways system. Codified missions include maintaining aids to navigation and ice operations.
Maritime security operations include activities to detect, deter, prevent, and disrupt terrorist attacks, and other criminal acts in the U.S. maritime domain. This includes the execution of anti-terrorism, response, and select recovery operations. This mission performs the operational element of the Coast Guard's Ports, Waterways, and Coastal Security mission and complements its Maritime Response and Prevention efforts. Codified missions include ports, waterways, and coastal security (response activities).
Coast Guard Defense Operations deploy the Coast Guard globally under the Department of Defense's unified combatant commands, where it operates under the joint force maritime component commands. Codified missions include defense readiness.
==== Coast Guard commands ====
The U.S. Coast Guard is organized into two area commands that cover the entire globe.
== Modernization and budget ==
=== Budget ===
The United States manages the world's largest military budget, followed by the People's Republic of China, India, United Kingdom, and Russia.
The James M. Inhofe National Defense Authorization Act for Fiscal Year 2023 established the topline defense budget as $857.9 billion, with the Department of Defense receiving $816.7 billion and the Department of Energy's national security programs receiving $30.3 billion, an 8% increase from Fiscal Year 2022.
The Department of the Air Force budget, unlike the Department of the Army or Department of the Navy has a sizable portion of "pass-through." This is money not controlled or used by the Air Force, but is instead passed to other Department of Defense agencies and can be up to 17% of the department's budget. This pass-through allocation gives the impression that the Air Force is the highest funded military department. It is actually the least funded.
=== Army modernization ===
The Army's modernization efforts, led by Army Futures Command, are centralized into six priorities. Each priority is led by a Cross Functional Team.
Long Range Precision Fires is the land service's top modernization priority, focusing on rebuilding its Field Artillery Branch in response to longer range Russian and Chinese artillery systems. The Extended Range Cannon Artillery program is developing a cannon artillery piece that can accurately fire at targets 70 kilometers away, an increase from the 30 kilometer distance of current cannon artillery. The Precision Strike Missile is a surface-to-surface guided missile intended to be fired from the current M270 Multiple Launch Rocket System and M142 HIMARS, replacing their current missiles and doubling the rate of fire. The Army is also working with the Missile Defense Agency, U.S. Navy, and U.S. Air Force to develop a common hypersonic glide body, which the Army will employ as part of the mobile ground launched Long-Range Hypersonic Weapon program. Finally, the Army is working to modify the U.S. Navy's RIM-174 Standard ERAM and UGM-109 Tomahawk land attack cruise missile for ground launch to provide the Army with mid-range artillery capability.
The Next Generation Combat Vehicle program is developing a family of fighting vehicles for the Armor Branch to increase firepower, speed, and survivability. The Optionally Manned Fighting Vehicle is intended to replace the M2 Bradley, while the Armored Multi-Purpose Vehicle will replace the M113 armored personnel carriers, which have been used since the Vietnam War. The three variants of the Armored Multi-Purpose Vehicle are general purpose, mission command, and medical treatment. The Mobile Protected Firepower is designed to be a light tank for Infantry Brigade Combat Teams. Finally, the Robotic Combat Vehicles are intended to come in light, medium, and heavy variants that will serve as scouts and escorts for crewed combat vehicles.
The Future Vertical Lift program is intended to replace the current helicopter fleet flown by the Army Aviation Branch.
The Future Long-Range Assault Aircraft is intended to replace the UH-60 Black Hawk and the Marine Corps UH-1Y Venom, with the Army selecting the Bell V-280 Valor tiltrotor aircraft as the winner. The Future Attack Reconnaissance Aircraft is intended to replace the AH-64 Apache in the attack and reconnaissance roles.
The Army is working to modernize its communication networks for the Army Signal Corps, including developing a Unified Network consisting of an integrated tactical network, an integrated enterprise network, and unified network-enabling capabilities. Other sub-efforts include developing a common operating environment, ensuring the network is interoperable with the other services and allied countries, and increasing the mobility and reducing the signature of its command posts. Efforts also include modernizing Global Positioning System technology to provide assured positioning, navigation, and timing, and working with the United States Intelligence Community and commercial space companies to increase the Army's access to space-based intelligence, surveillance, and reconnaissance capabilities.
Recognizing that that United States is unlikely to have uncontested air superiority, the Army is undergoing a mass revitalization of its air and missile defense enterprise through the Air Defense Artillery Branch.
The first layer of defense is the Ballistic Low-Altitude Drone Engagement, which will be mounted on the Common Remotely Operated Weapon Station and is designed to engage small unmanned aerial vehicles. The second layer is the Multi-Mission High Energy Laser, which will intercept small drones and munitions. The third and fourth layers comprise the Maneuver Air Defense Technology and Next-Generation Fires Radar, which will be integrated into short range air defense systems. The fifth layer puts a High-Energy Laser Tactical Vehicle Demonstrator onto a Medium Tactical Vehicle, while the sixth layer encompasses the Low-Cost Extended-Range Air Defense to supplement the MIM-104 Patriot missiles.
Finally, the Army is looking to improve the equipment of its soldiers in the Infantry Branch with the Next Generation Squad Weapon, the Integrated Visual Augmentation System, and the Synthetic Training Environment. In 2022, the Army selected the SIG Sauer's XM7 rifle and XM250 light machine gun to replace the M4 carbine and the M249 light machine gun through the Next Generation Squad Weapon program.
=== Marine Corps modernization ===
The Marine Corps modernization is being executed under the aegis of Force Design 2030, which is intended to return the service to its naval and amphibious roots serving as a "stand-in" force within contested areas of the maritime littorals. As part of this effort, the Marine Corps has begun establishing naval-focused Marine Littoral Regiments, consisting of a Littoral Combat Team, Littoral Anti-Air Battalion, and a Combat Logistics Battalion. The Littoral Combat Team is organized around an infantry battalion with an anti-ship missile battery, focused on conducting sea denial operations in support of the Navy.
The Marine Corps is in the process of acquiring the Amphibious Combat Vehicle, which is slated to replace the aging Assault Amphibious Vehicle. The Amphibious Combat Vehicle is intended to support the Marines during amphibious assaults and once they have reached shore. The Marine Corps has also adopted the Naval Strike Missile which is fielded from a modified Joint Light Tactical Vehicle as part of the Marines' artillery battalions. The concept is that small mobile units of Marines would move around different islands and shorelines with these weapons to fire on adversary ships.
Marine Corps aviation is also in the process of acquiring the CH-53K King Stallion helicopter for heavy lift, replacing the current CH-53E Super Stallion in the role. The Marine Corps is also looking to replace its UH-1Y Venom helicopters through the Future Vertical Lift program and is in the process of acquiring a significant number of unmanned aerial vehicles, such as the MQ-9 Reaper.
=== Navy modernization ===
Like the Marine Corps, the Navy is in the process of overhauling and modernizing its fleet with a renewed focus. While the Navy is continuing to purchase Arleigh Burke-class destroyers, it is embarking on the DDG(X) program of guided missile destroyers to replace them and the Ticonderoga-class cruisers. The DDG(X) will include directed energy weapons and potentially hypersonic weapons.
The Constellation-class frigates will be the first frigates in the U.S. Navy since the Oliver Hazard Perry-class frigates were retired. The Constellation-class frigates are based on the Italian FREMM multipurpose frigates and will replace the littoral combat ships.
The Navy is starting development on the SSN(X) attack submarines, intended to replace the Virginia-class and Seawolf-class submarines. The Columbia-class submarines will begin replacing the Ohio-class ballistic missile submarines. The acquisition of the Columbia-class submarines is the first priority of the Navy.
With Naval Aviation, the service is continuing to procure additional Gerald R. Ford-class aircraft carriers and F-35C Lightning II stealth fighters. Ultimately, the F/A-XX program is intended to produce a sixth-generation fighter to replace the legacy F/A-18E/F Super Hornets as part of the Carrier Air Wing and is using the Future Vertical Lift program to replace its fleet of SH-60 Seahawk helicopters.
The service is also investing heavily in unmanned platforms, such as unmanned surface vehicles, using the Ghost Fleet Overlord to test the concept. It is also fielding unmanned aerial vehicles, such as the land-based MQ-4C Triton for maritime patrol and the carrier-based MQ-25A Stingray for aerial refueling, replacing the F/A-18F in the role.
=== Air Force modernization ===
The B-21 Raider stealth bomber is the first new Air Force bomber since the B-2A Spirit. The B-21 will replace the B-2 and the B-1B Lancer, flying alongside the B-52 Stratofortress. The development of the B-21 Raider was led by the Department of the Air Force Rapid Capabilities Office. The service is also developing the LGM-35 Sentinel intercontinental ballistic missile to replace the LGM-30G Minuteman IIIs.
The U.S. Air Force is also in the process of developing the Next Generation Air Dominance program, which will produce a sixth generation fighter to replace the F-22 Raptor. The service is also procuring the fourth generation F-15EX Eagle II to replace the aging F-15C Eagle and F-15E Strike Eagle. It is procuring the T-7A Red Hawk trainer jet to replace the 1950s-era T-38 Talon.
While not an aircraft, the Air Force is investing in developing the AIM-260 Joint Advanced Tactical Missile to replace or supplement the AIM-120 AMRAAM for its fighter forces. It is also procuring the AGM-181 Long Range Stand Off Weapon to replace the AGM-86 ALCM as a nuclear air-launched cruise missile for the B-21 Raider and the B-52 Stratofortress. The air service is investing in hypersonic weapons, with the AGM-183 Air-Launched Rapid Response Weapon, the Hypersonic Air-breathing Weapon Concept, and the Hypersonic Attack Cruise Missile in development.
=== Space Force modernization ===
The U.S. Space Force is undergoing intensive modernization efforts. The Deep Space Advanced Radar Capability (DARC) is intended to track objects in geosynchronous orbit with three sites, one in the United States, one in the Indo-Pacific, and one in Europe.
Oracle, a spacecraft developed by the Air Force Research Laboratory for the Space Force, will demonstrate technologies that the space service needs for cislunar domain awareness – tracking objects outside of geosynchronous orbit and between Earth and the Moon. The spacecraft itself will launch to an area of gravitational stability between the Earth and the Moon to conduct operations, using a wide-field sensor and a more sensitive narrow-field sensor to discover and maintain custody of objects operating in this region. Oracle will directly support NASA's Artemis program as it returns to the Moon and track potentially hazardous near-Earth objects in support of planetary defense operations.
Also an Air Force Research Laboratory program for the Space Force, Arachne is the keystone experiment in the Space Solar Power Incremental Demonstrations and Research Project, which aims to prove and mature essential technologies for a prototype space-based solar power transmission system capable of powering a forward operating base. Arachne will specifically demonstrate and mature technologies related to more efficient energy generation, radio frequency forming, and radio frequency beaming. Current forward operation bases rely on significant logistics convoys to transport fuel for power – space-based solar power would move these supply lines to space, where they cannot be easily attacked. Space Force provided space-based solar power may transition to civilian use in the same vein as GPS. Other space-based power beaming demonstrations include the Space Power InfraRed Regulation and Analysis of Lifetime (SPIRRAL) and Space Power INcremental DepLoyable Experiment (SPINDLE) experiments.
The Navigation Technology Satellite-3 (NTS-3), building on the Space Force's Global Positioning System constellation, is an Air Force Research Laboratory spacecraft that will operate in geosynchronous orbit to test advanced techniques and technologies to detect and mitigate interference to positioning, navigation, and timing capabilities and increase system resiliency for military, civil, and commercial users. NTS-3 is a Vanguard program, described as aiming to deliver potentially game changing capabilities.
The Space Force's Rocket Cargo program is another Air Force Research Laboratory Vanguard program, focused on leasing space launch services to quickly transport military materiel to ports across the globe. If proven viable, the Space Force's Space Systems Command will be responsible for transitioning it to a program of record. United States Transportation Command would be the primary user of this capability, rapidly launching up to 100 tons of cargo anywhere in the world.
== Personnel ==
The U.S. Armed Forces is the world's third largest military by active personnel, after the Chinese People's Liberation Army and the Indian Armed Forces, consisting of 1,359,685 servicemembers in the regular armed forces with an additional 799,845 servicemembers in the reserves as of 28 February 2019.
While the United States Armed Forces is an all-volunteer military, conscription through the Selective Service System can be enacted at the president's request and Congress' approval, with all males ages 18 through 25 living in the United States required to register with the Selective Service. Although the constitutionality of registering only males for Selective Service was challenged by federal district court in 2019, its legality was upheld by a federal appeals court in 2020.
As in most militaries, members of the U.S. Armed Forces hold a rank, either that of officer, warrant officer or enlisted, to determine seniority and eligibility for promotion. Those who have served are known as veterans. Rank names may be different between services, but they are matched to each other by their corresponding paygrade. Officers who hold the same rank or paygrade are distinguished by their date of rank to determine seniority. Officers who serve in certain positions of office of importance set by law, outrank all other officers on active duty of the same rank and paygrade, regardless of their date of rank.
=== Personnel by service ===
Total number of authorized personnel in FY23.
=== Rank structure ===
Rank in the United States Armed Forces is split into three distinct categories: officers, warrant officers, and enlisted personnel. Officers are the leadership of the military, holding commissions from the president of the United States and confirmed to their rank by the Senate. Warrant officers hold a warrant from the secretaries of the military departments, serving as specialists in certain military technologies and capabilities. Upon promotion to chief warrant officer 2, they gain a commission from the president of the United States. Enlisted personnel constitute the majority of the armed forces, serving as specialists and tactical-level leaders until they become senior non-commissioned officers or senior petty officers. Military ranks across the services can be compared by U.S. Uniformed Services pay grade or NATO rank code.
==== Officer corps ====
Officers represent the top 18% of the armed forces, serving in leadership and command roles. Officers are divided into three categories:
O-1 to O-3: Company grade officers in the Army, Marine Corps, Air Force, and Space Force or junior officers in the Navy and the Coast Guard.
O-4 to O-6: Field grade officers in the Army, Marine Corps, Air Force, and Space Force or mid-grade officers in the Navy and Coast Guard.
O-7 to O-10: General officers in the Army, Marine Corps, Air Force, and Space Force or flag officers in the Navy and Coast Guard.
Officers are typically commissioned as second lieutenants or ensigns with a bachelor's degree after several years of training and education or directly commissioned from civilian life into a specific specialty, such as a medical professional, lawyer, chaplain, or cyber specialist.
Officers are commissioned through the United States service academies, Reserve Officer Training Corps programs, and the Officer Candidate and Officer Training Schools. During a time of war, officers may be promoted to five-star ranks, with general of the Army, fleet admiral, and general of the Air Force the only five-star ranks currently authorized.
==== Warrant officer corps ====
Warrant officers are specialists, accounting for only 8% of the officer corps. Warrant officers hold warrants from their service secretary and are specialists and experts in certain military technologies or capabilities. The lowest-ranking warrant officers serve under a warrant, but they receive commissions from the president upon promotion to chief warrant officer 2. They derive their authority from the same source as commissioned officers but remain specialists, in contrast to commissioned officers, who are generalists. There are no warrant officers in the Air Force or Space Force.
Warrant officers are typically non-commissioned officers before being selected, with the exception of Army Aviation where any enlisted grade can apply for a warrant. Army Warrant officers attend the Army Warrant Officer Candidate School.
==== Enlisted corps ====
Enlisted personnel comprise 82% of the armed forces, serving as specialists and tactical leaders. Enlisted personnel are divided into three categories:
E-1 to E-3/4: Junior enlisted personnel are usually in initial training or at their first assignment. E-1 to E-3 in the Marine Corps, Navy, and Coast Guard, and E-1 to E-4 in the Army, Air Force, and Space Force. In the Army, specialists (E-4) are considered to be junior enlisted, while corporals (E-4) are non-commissioned officers.
E-4/5 to E-6: Non-commissioned officers in the Army, Marine Corps, Air Force, and Space Force and petty officers in the Navy and Coast Guard. In the Air Force and Space Force, E-5 is the first non-commissioned officer rank. Non-commissioned officers and petty officers are responsible for tactical leadership.
E-7 to E-9: Senior non-commissioned officers in the Army, Marine Corps, Air Force, and Space Force and chief petty officers in the Navy and Coast Guard. Serve as senior enlisted advisors to officers.
The rank of senior enlisted advisor is the highest rank in each service, serving as the primary advisor to its service secretary and service chief on enlisted matters. Prior to entering service, enlisted personnel must complete their service's basic training. In the Army, after completing Basic Combat Training, recruits then go to advanced individual training for their military occupational specialty.
Upon completion of Marine Corps Recruit Training, Infantry Marines attend the School of Infantry. Non-infantry Marines complete Marine Combat Training before advancing to technical schools for their Military Occupational Specialty. In the Navy, after completing Recruit Training, sailors advance to their "A" schools to complete training for their rating. In the Air Force and Space Force, recruits complete combined Basic Military Training before going to technical training for their Air Force Specialty Codes. In the Coast Guard, after completing Recruit Training, sailors advance to their "A" schools to complete training for their rating.
=== Women in the armed forces ===
All branches of the U.S. military enlisted women during World War II. The Woman's Army Auxiliary Corps was established by the Army in 1942. Also formed during this time were the Women's Airforce Service Pilots (WASPs), the Navy's Women Accepted for Volunteer Emergency Services (WAVES), the Marine Corps Women's Reserve, and the Coast Guard Women's Reserve (SPARS). Women saw combat during World War II, first as nurses in the Pearl Harbor attacks on 7 December 1941. In 1944, WACs arrived in the Pacific and in Normandy. During the war, 67 Army nurses and 16 Navy nurses were captured and spent three years as Japanese prisoners of war. There were 350,000 American women who served during World War II, and 16 were killed on duty. In total, they gained over 1,500 medals, citations, and commendations.
After World War II, demobilization led to the vast majority of serving women being returned to civilian life. Law 625, The Women's Armed Services Act of 1948, was signed by President Harry S. Truman, allowing women to serve in the U.S. Armed Forces in fully integrated units during peace time, with only the WAC remaining a separate female unit. During the Korean War of 1950–1953, many women served in the Mobile Army Surgical Hospitals. During the Vietnam War, 600 women served in the country as part of the Air Force, along with 500 members of the WAC and over 6,000 medical personnel and support staff. The Ordnance Corps began accepting female missile technicians in 1974. Female crewmembers and officers were accepted into Field Artillery missile units.
In 1974, the first six female naval aviators earned their wings as Navy pilots. The Congressionally mandated prohibition on women in combat places limitations on the pilots' advancement, but at least two retired as captains. The role of women in the U.S. Armed Forces received global media attention during the 1991 Gulf War, though their perception in media was skewed during this time period as little media attention was given to the situations where women faced combat.
In 1991, women were permitted to fly military aircraft. Since 1994, women have been permitted to serve on U.S. combat ships. In 2010, the ban on women serving on submarines was lifted.
On 3 December 2015, U.S. defense secretary Ashton Carter announced that all military combat positions would become available to women. This gave women access to the roughly 10% of military jobs which were previously closed to them. These restrictions were supported by studies concluding that mixed gender units are less capable in combat. The various military services were given until January 2016 to provide plans on how they would enforce the policy change. Many women believed this would allow them to improve their positions in the military, since most high-ranking officers start in combat positions. Draft registration for females was recommended by the National Commission on Military, National, and Public Service and has been proposed, but never implemented.
No woman has ever become a Navy SEAL. However, in July 2021, the first woman graduated from the Naval Special Warfare (NSW) training program to become a Special Warfare Combatant craft Crewman (SWCC). The SWCC directly supports the SEALs and other special forces units, and are experts in covert insertion and extraction special operation tactics.
Despite concerns of a gender gap, all personnel both men and women, at the same rank and time of service, are compensated the same across all branches. On 1 June 2022, ADM Linda L. Fagan assumed command of the U.S. Coast Guard, becoming not only the first woman to serve as Commandant of the Coast Guard, but also the first woman in American history to serve as a service chief in the U.S. Military.
A study conducted by the RAND Corporation suggests that women who make the military their careers experience improved rates of promotion.
As per the DoD's report on sexual assault within the U.S. Army for fiscal year 2019, 7,825 cases had been reported. This represented a 3% increase relative to the 2018 report.
As of 2022, there are 228,966 women in the military, representing 17.5% of the total active duty force. Since 2021, the percentage of women on active duty service has increased slightly, by 0.3%. Since 2005, the population of active duty women has increased by 2.9%.
== Order of precedence ==
Under Department of Defense regulation, the various components of the U.S. Armed Forces have a set order of seniority. Examples of the use of this system include the display of service flags, and placement of soldiers, marines, sailors, airmen, guardians, and coast guardsmen in formation.
Cadets, U.S. Military Academy
Midshipmen, U.S. Naval Academy
Cadets, U.S. Air Force Academy
Cadets, U.S. Coast Guard Academy
Midshipmen, U.S. Merchant Marine Academy
United States Army
United States Marine Corps
United States Navy
United States Air Force
United States Space Force
United States Coast Guard
Army National Guard
United States Army Reserve
United States Marine Corps Reserve
United States Navy Reserve
Air National Guard
United States Air Force Reserve
United States Coast Guard Reserve
Other training and auxiliary organizations of the Army, Marine Corps, Merchant Marine, Civil Air Patrol, and Coast Guard Auxiliary, as in the preceding order.
While the U.S. Navy is older than the Marine Corps, the Marine Corps takes precedence due to previous inconsistencies in the Navy's birth date. The Marine Corps has recognized its observed birth date on a more consistent basis. The Second Continental Congress is considered to have established the Navy on 13 October 1775 by authorizing the purchase of ships, but did not actually pass the "Rules for the Regulation of the Navy of the United Colonies" until 27 November 1775. The Marine Corps was established by an act of the Second Continental Congress on 10 November 1775. The Navy did not officially recognize 13 October 1775 as its birth date until 1972, when then–chief of naval operations Admiral Elmo Zumwalt authorized it to be observed as such.
The Coast Guard is normally situated after the Space Force, but if it is moved to the Department of the Navy, then its place in the order of precedence changes to being situated after the Navy and before the Air Force.
== See also ==
== Notes ==
== Citations ==
== External links ==
Official U.S. Department of Defense website | The United States Armed Forces are the military forces of the United States. The armed forces consist of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. All six armed services are among the eight uniformed services of the United States, along with the U.S. Public Health Service Commissioned Corps and the NOAA Commissioned Officer Corps.
Each of the different military services is assigned a role and domain. The Army conducts land operations. The Navy and Marine Corps conduct maritime operations, the Marine Corps specializing in amphibious and maritime littoral operations primarily for supporting the Navy. The Air Force conducts air operations. The Space Force conducts space operations. The Coast Guard is unique in that it specializes in maritime operations and is also a law enforcement agency.
From their inception during the American Revolutionary War, the U.S. Armed Forces have played a decisive role in the country's history. They helped forge a sense of national unity and identity through victories in the early-19th-century First and Second Barbary Wars. They played a critical role in the territorial evolution of the U.S., including the American Civil War. The National Security Act of 1947 created the modern U.S. military framework, establishing the National Military Establishment (later the Department of Defense or DoD) headed by the secretary of defense and creating both the U.S. Air Force and National Security Council; in 1949, an amendment to the act merged the cabinet-level departments of the Army, Navy, and Air Force into the DoD.
The president of the U.S. is the commander-in-chief of the armed forces and forms military policy with the DoD and Department of Homeland Security (DHS), both federal executive departments, acting as the principal organs by which military policy is carried out.
The U.S. Armed Forces are one of the world's largest military forces in terms of personnel. They draw their personnel from a large pool of professional volunteers. The U.S. has used military conscription, but not since 1973. The Selective Service System retains the power to conscript males, requiring the registration of all male citizens and residents living in the U.S. between the ages of 18 and 25.
The U.S. Armed Forces are considered the world's most powerful military, especially since the end of the Cold War. The military expenditure of the U.S. was US$916 billion in 2023, the highest in the world, accounting for 37% of the world's defense expenditures. The U.S. Armed Forces has significant capabilities in both defense and power projection due to its large budget, resulting in advanced and powerful technologies which enable widespread deployment of the force around the world, including around 800 military bases outside the U.S. The U.S. Air Force is the world's largest air force, followed by the U.S. Army Aviation Branch. The U.S. Naval Air Forces is the fourth-largest air arm in the world and is the largest naval aviation service, while U.S. Marine Corps Aviation is the world's seventh-largest air arm. The U.S. Navy is the world's largest navy by tonnage. The U.S. Coast Guard is the world's 12th-largest maritime force. The U.S. Space Force is the world's only active independent space force.
| 25 |
304 | lichen | Flechte (wiktionary) | From Middle High German vlehte. Compare Dutch vlecht, Gothic 𐍆𐌻𐌰𐌷𐍄𐌰 (flahta). This etymology is incomplete. You can help Wiktionary by elaborating on the origins of this term.
IPA(key): [ˈflɛçtə]
Rhymes: -ɛçtə
Flechte f (genitive Flechte, plural Flechten)
lichen
plait
“Flechte” in Duden online
“Flechte” in Digitales Wörterbuch der deutschen Sprache | From Middle High German vlehte. Compare Dutch vlecht, Gothic 𐍆𐌻𐌰𐌷𐍄𐌰 (flahta). This etymology is incomplete. You can help Wiktionary by elaborating on the origins of this term.
IPA(key): [ˈflɛçtə]
Rhymes: -ɛçtə
Flechte f (genitive Flechte, plural Flechten)
lichen
plait
“Flechte” in Duden online
“Flechte” in Digitales Wörterbuch der deutschen Sprache | 10 |
305 | lichen | flechte (wiktionary) | flechte
inflection of flechten:
first-person singular present
first/third-person singular subjunctive I | flechte
inflection of flechten:
first-person singular present
first/third-person singular subjunctive I | 2 |
306 | lichen | lichen (wiktionary) | Borrowed from Latin līchēn, from Ancient Greek λειχήν (leikhḗn), from λείχω (leíkhō, “to lick”). Originally used of liverwort; the modern sense first recorded 1715.
enPR: lī'kən, IPA(key): /ˈlaɪ.kən/
enPR: lĭ'chən, (also, especially in the UK) IPA(key): /ˈlɪ.tʃən/
Rhymes: -aɪkən, -ɪtʃən
Homophones: liken, lycan
lichen (countable and uncountable, plural lichens or lichen)
Any of many symbiotic organisms, being associations of algae and fungi, often found as white or yellow-to-blue–green patches on rocks, old walls, etc.
(figurative) Something which gradually spreads across something else, causing damage.
Synonym: cancer
(symbiotic organism): macrolichen, microlichen
lichen on Wikipedia.Wikipedia
algae
fungus
Iceland moss
moss
reindeer moss
Borrowed from Latin lichen, from Ancient Greek λειχήν (leikhḗn).
IPA(key): /li.kɛn/
lichen m (plural lichens)
lichen
lichen plan
lichénique
“lichen”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.
chelin
Borrowed from Ancient Greek λειχήν (leikhḗn).
(Classical Latin) IPA(key): /ˈliː.kʰeːn/, [ˈlʲiːkʰeːn]
(modern Italianate Ecclesiastical) IPA(key): /ˈli.ken/, [ˈliːken]
līchēn m (genitive līchēnos or līchēnis); third declension
(literally) a cryptogamic species of vegetation growing on trees, lichen
(transferred sense, medicine) an eruption on the skin of men and beasts, a tetter, ringworm
(and especially) a callous excrescence upon the leg of a horse, used as a medicine
Third-declension noun (Greek-type, normal variant or non-Greek-type).
līchēnifōrmis
līchēna
līchēnicos
English: lichen
French: lichen
Portuguese: líquen
Spanish: liquen
“līchēn”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
līchēn in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette, page 909/3.
“līchēn” on page 1,029/1 of the Oxford Latin Dictionary (1st ed., 1968–82)
lichen (third-person singular present licht, past participle gelicht, auxiliary verb hunn)
(transitive, slang) to kick out, to throw out, to sack
erausgeheien
lanteren
schassen
(transitive) to lift (a little)
(reflexive, slang) to get up, to leave (as a guest), to get to one's feet
(reflexive) to lift (fog, mist)
sech hiewen
Borrowed from French lichen.
lichen m (plural licheni)
lichen | Borrowed from Latin līchēn, from Ancient Greek λειχήν (leikhḗn), from λείχω (leíkhō, “to lick”). Originally used of liverwort; the modern sense first recorded 1715.
enPR: lī'kən, IPA(key): /ˈlaɪ.kən/
enPR: lĭ'chən, (also, especially in the UK) IPA(key): /ˈlɪ.tʃən/
Rhymes: -aɪkən, -ɪtʃən
Homophones: liken, lycan
lichen (countable and uncountable, plural lichens or lichen)
Any of many symbiotic organisms, being associations of algae and fungi, often found as white or yellow-to-blue–green patches on rocks, old walls, etc.
(figurative) Something which gradually spreads across something else, causing damage.
Synonym: cancer
(symbiotic organism): macrolichen, microlichen
lichen on Wikipedia.Wikipedia
algae
fungus
Iceland moss
moss
reindeer moss
Borrowed from Latin lichen, from Ancient Greek λειχήν (leikhḗn).
IPA(key): /li.kɛn/
lichen m (plural lichens)
lichen
lichen plan
lichénique
“lichen”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.
chelin
Borrowed from Ancient Greek λειχήν (leikhḗn).
(Classical Latin) IPA(key): /ˈliː.kʰeːn/, [ˈlʲiːkʰeːn]
(modern Italianate Ecclesiastical) IPA(key): /ˈli.ken/, [ˈliːken]
līchēn m (genitive līchēnos or līchēnis); third declension
(literally) a cryptogamic species of vegetation growing on trees, lichen
(transferred sense, medicine) an eruption on the skin of men and beasts, a tetter, ringworm
(and especially) a callous excrescence upon the leg of a horse, used as a medicine
Third-declension noun (Greek-type, normal variant or non-Greek-type).
līchēnifōrmis
līchēna
līchēnicos
English: lichen
French: lichen
Portuguese: líquen
Spanish: liquen
“līchēn”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
līchēn in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette, page 909/3.
“līchēn” on page 1,029/1 of the Oxford Latin Dictionary (1st ed., 1968–82)
lichen (third-person singular present licht, past participle gelicht, auxiliary verb hunn)
(transitive, slang) to kick out, to throw out, to sack
erausgeheien
lanteren
schassen
(transitive) to lift (a little)
(reflexive, slang) to get up, to leave (as a guest), to get to one's feet
(reflexive) to lift (fog, mist)
sech hiewen
Borrowed from French lichen.
lichen m (plural licheni)
lichen | 42 |
307 | lichen | Lichen (wikipedia) | A lichen ( LY-kən, UK also LITCH-ən) is a symbiosis of algae or cyanobacteria living among filaments of multiple fungi species, along with a yeast embedded in the cortex or "skin", in a mutualistic relationship. Lichens are important actors in nutrient cycling and act as producers which many higher trophic feeders feed on, such as reindeer, gastropods, nematodes, mites, and springtails. Lichens have properties different from those of their component organisms. They come in many colors, sizes, and forms and are sometimes plant-like, but are not plants. They may have tiny, leafless branches (fruticose); flat leaf-like structures (foliose); grow crust-like, adhering tightly to a surface (substrate) like a thick coat of paint (crustose); have a powder-like appearance (leprose); or other growth forms.
A macrolichen is a lichen that is either bush-like or leafy; all other lichens are termed microlichens. Here, "macro" and "micro" do not refer to size, but to the growth form. Common names for lichens may contain the word moss (e.g., "reindeer moss", "Iceland moss"), and lichens may superficially look like and grow with mosses, but they are not closely related to mosses or any plant.: 3 Lichens do not have roots that absorb water and nutrients as plants do,: 2 but like plants, they produce their own nutrition by photosynthesis. When they grow on plants, they do not live as parasites, but instead use the plant's surface as a substrate.
Lichens occur from sea level to high alpine elevations, in many environmental conditions, and can grow on almost any surface. They are abundant growing on bark, leaves, mosses, or other lichens and hanging from branches "living on thin air" (epiphytes) in rainforests and in temperate woodland. They grow on rock, walls, gravestones, roofs, exposed soil surfaces, rubber, bones, and in the soil as part of biological soil crusts. Various lichens have adapted to survive in some of the most extreme environments on Earth: arctic tundra, hot dry deserts, rocky coasts, and toxic slag heaps. They can even live inside solid rock, growing between the grains (endolithic).
There are about 20,000 known species. Some lichens have lost the ability to reproduce sexually, yet continue to speciate. They can be seen as being relatively self-contained miniature ecosystems, where the fungi, algae, or cyanobacteria have the potential to engage with other microorganisms in a functioning system that may evolve as an even more complex composite organism. Lichens may be long-lived, with some considered to be among the oldest living things. They are among the first living things to grow on fresh rock exposed after an event such as a landslide. The long life-span and slow and regular growth rate of some species can be used to date events (lichenometry). Lichens are a keystone species in many ecosystems and benefit trees and birds.
== Etymology and pronunciation ==
The English word lichen derives from the Greek λειχήν leichēn ("tree moss, lichen, lichen-like eruption on skin") via Latin lichen. The Greek noun, which literally means "licker", derives from the verb λείχειν leichein, "to lick". In American English, "lichen" is pronounced the same as the verb "liken" (). In British English, both this pronunciation and one rhyming with "kitchen" () are used.
== Anatomy and morphology ==
=== Growth forms ===
Lichens grow in a wide range of shapes and forms; this external appearance is known as their morphology. The shape of a lichen is usually determined by the organization of the fungal filaments. The nonreproductive tissues, or vegetative body parts, are called the thallus. Lichens are grouped by thallus type, since the thallus is usually the most visually prominent part of the lichen. Thallus growth forms typically correspond to a few basic internal structure types. Common names for lichens often come from a growth form or color that is typical of a lichen genus.
Common groupings of lichen thallus growth forms are:
fruticose – growing like a tuft or multiple-branched leafless mini-shrub, upright or hanging down, 3-dimensional branches with nearly round cross section (terete) or flattened
foliose – growing in 2-dimensional, flat, leaf-like lobes
crustose – crust-like, adhering tightly to a surface (substrate) like a thick coat of paint
squamulose – formed of small leaf-like scales crustose below but free at the tips
leprose – powdery
gelatinous – jelly-like
filamentous – stringy or like matted hair
byssoid – wispy, like teased wool
structureless
There are variations in growth types in a single lichen species, grey areas between the growth type descriptions, and overlapping between growth types, so some authors might describe lichens using different growth type descriptions.
When a crustose lichen gets old, the center may start to crack up like old-dried paint, old-broken asphalt paving, or like the polygonal "islands" of cracked-up mud in a dried lakebed. This is called being rimose or areolate, and the "island" pieces separated by the cracks are called areolas. The areolas appear separated, but are (or were) connected by an underlying prothallus or hypothallus. When a crustose lichen grows from a center and appears to radiate out, it is called crustose placodioid. When the edges of the areolas lift up from the substrate, it is called squamulose.: 159
These growth form groups are not precisely defined. Foliose lichens may sometimes branch and appear to be fruticose. Fruticose lichens may have flattened branching parts and appear leafy. Squamulose lichens may appear where the edges lift up. Gelatinous lichens may appear leafy when dry.: 159
The thallus is not always the part of the lichen that is most visually noticeable. Some lichens can grow inside solid rock between the grains (endolithic lichens), with only the sexual fruiting part visible growing outside the rock. These may be dramatic in color or appearance. Forms of these sexual parts are not in the above growth form categories. The most visually noticeable reproductive parts are often circular, raised, plate-like or disc-like outgrowths, with crinkly edges, and are described in sections below.
=== Color ===
Lichens come in many colors.: 4 Coloration is usually determined by the photosynthetic component. Special pigments, such as yellow usnic acid, give lichens a variety of colors, including reds, oranges, yellows, and browns, especially in exposed, dry habitats. In the absence of special pigments, lichens are usually bright green to olive gray when wet, gray or grayish-green to brown when dry. This is because moisture causes the surface skin (cortex) to become more transparent, exposing the green photobiont layer. Different colored lichens covering large areas of exposed rock surfaces, or lichens covering or hanging from bark can be a spectacular display when the patches of diverse colors "come to life" or "glow" in brilliant displays following rain.
Different colored lichens may inhabit different adjacent sections of a rock face, depending on the angle of exposure to light. Colonies of lichens may be spectacular in appearance, dominating much of the surface of the visual landscape in forests and natural places, such as the vertical "paint" covering the vast rock faces of Yosemite National Park.
Color is used in identification.: 4 The color of a lichen changes depending on whether the lichen is wet or dry. Color descriptions used for identification are based on the color that shows when the lichen is dry. Dry lichens with a cyanobacterium as the photosynthetic partner tend to be dark grey, brown, or black.
The underside of the leaf-like lobes of foliose lichens is a different color from the top side (dorsiventral), often brown or black, sometimes white. A fruticose lichen may have flattened "branches", appearing similar to a foliose lichen, but the underside of a leaf-like structure on a fruticose lichen is the same color as the top side. The leaf-like lobes of a foliose lichen may branch, giving the appearance of a fruticose lichen, but the underside will be a different color from the top side.
The sheen on some jelly-like gelatinous lichens is created by mucilaginous secretions.
=== Internal structure ===
A lichen consists of a simple photosynthesizing organism, usually a green alga or cyanobacterium, surrounded by filaments of a fungus. Generally, most of a lichen's bulk is made of interwoven fungal filaments, but this is reversed in filamentous and gelatinous lichens. The fungus is called a mycobiont. The photosynthesizing organism is called a photobiont. Algal photobionts are called phycobionts. Cyanobacteria photobionts are called cyanobionts.
The part of a lichen that is not involved in reproduction, the "body" or "vegetative tissue" of a lichen, is called the thallus. The thallus form is very different from any form where the fungus or alga are growing separately. The thallus is made up of filaments of the fungus called hyphae. The filaments grow by branching then rejoining to create a mesh, which is called being "anastomosed". The mesh of fungal filaments may be dense or loose.
Generally, the fungal mesh surrounds the algal or cyanobacterial cells, often enclosing them within complex fungal tissues that are unique to lichen associations. The thallus may or may not have a protective "skin" of densely packed fungal filaments, often containing a second fungal species, which is called a cortex. Fruticose lichens have one cortex layer wrapping around the "branches". Foliose lichens have an upper cortex on the top side of the "leaf", and a separate lower cortex on the bottom side. Crustose and squamulose lichens have only an upper cortex, with the "inside" of the lichen in direct contact with the surface they grow on (the substrate). Even if the edges peel up from the substrate and appear flat and leaf-like, they lack a lower cortex, unlike foliose lichens. Filamentous, byssoid, leprose, gelatinous, and other lichens do not have a cortex; in other words, they are ecorticate.
Fruticose, foliose, crustose, and squamulose lichens generally have up to three different types of tissue, differentiated by having different densities of fungal filaments. The top layer, where the lichen contacts the environment, is called a cortex. The cortex is made of densely tightly woven, packed, and glued together (agglutinated) fungal filaments. The dense packing makes the cortex act like a protective "skin", keeping other organisms out, and reducing the intensity of sunlight on the layers below. The cortex layer can be up to several hundred micrometers (μm) in thickness (less than a millimeter). The cortex may be further topped by an epicortex of secretions, not cells, 0.6–1 μm thick in some lichens. This secretion layer may or may not have pores.
Below the cortex layer is a layer called the photobiontic layer or symbiont layer. The symbiont layer has less densely packed fungal filaments, with the photosynthetic partner embedded in them. The less dense packing allows air circulation during photosynthesis, similar to the anatomy of a leaf. Each cell or group of cells of the photobiont is usually individually wrapped by hyphae, and in some cases penetrated by a haustorium. In crustose and foliose lichens, algae in the photobiontic layer are diffuse among the fungal filaments, decreasing in gradation into the layer below. In fruticose lichens, the photobiontic layer is sharply distinct from the layer below.
The layer beneath the symbiont layer is called the medulla. The medulla is less densely packed with fungal filaments than the layers above. In foliose lichens, as in Peltigera,: 159 there is usually another densely packed layer of fungal filaments called the lower cortex. Root-like fungal structures called rhizines (usually): 159 grow from the lower cortex to attach or anchor the lichen to the substrate. Fruticose lichens have a single cortex wrapping all the way around the "stems" and "branches". The medulla is the lowest layer, and may form a cottony white inner core for the branchlike thallus, or it may be hollow.: 159 Crustose and squamulose lichens lack a lower cortex, and the medulla is in direct contact with the substrate that the lichen grows on.
In crustose areolate lichens, the edges of the areolas peel up from the substrate and appear leafy. In squamulose lichens the part of the lichen thallus that is not attached to the substrate may also appear leafy. But these leafy parts lack a lower cortex, which distinguishes crustose and squamulose lichens from foliose lichens. Conversely, foliose lichens may appear flattened against the substrate like a crustose lichen, but most of the leaf-like lobes can be lifted up from the substrate because it is separated from it by a tightly packed lower cortex.
Gelatinous,: 159 byssoid, and leprose lichens lack a cortex (are ecorticate), and generally have only undifferentiated tissue, similar to only having a symbiont layer.
In lichens that include both green algal and cyanobacterial symbionts, the cyanobacteria may be held on the upper or lower surface in small pustules called cephalodia.
Pruinia is a whitish coating on top of an upper surface. An epinecral layer is "a layer of horny dead fungal hyphae with indistinct lumina in or near the cortex above the algal layer".
In August 2016, it was reported that some macrolichens have more than one species of fungus in their tissues.
== Physiology ==
=== Symbiotic relation ===
Lichens are fungi that have discovered agriculture
A lichen is a composite organism that emerges from algae or cyanobacteria living among the filaments (hyphae) of the fungi in a mutually beneficial symbiotic relationship. The fungi benefit from the carbohydrates produced by the algae or cyanobacteria via photosynthesis. The algae or cyanobacteria benefit by being protected from the environment by the filaments of the fungi, which also gather moisture and nutrients from the environment, and (usually) provide an anchor to it. Although some photosynthetic partners in a lichen can survive outside the lichen, the lichen symbiotic association extends the ecological range of both partners, whereby most descriptions of lichen associations describe them as symbiotic. Both partners gain water and mineral nutrients mainly from the atmosphere, through rain and dust. The fungal partner protects the alga by retaining water, serving as a larger capture area for mineral nutrients and, in some cases, provides minerals obtained from the substrate. If a cyanobacterium is present, as a primary partner or another symbiont in addition to a green alga as in certain tripartite lichens, they can fix atmospheric nitrogen, complementing the activities of the green alga.
In three different lineages the fungal partner has independently lost the mitochondrial gene atp9, which has key functions in mitochondrial energy production. The loss makes the fungi completely dependent on their symbionts.
The algal or cyanobacterial cells are photosynthetic and, as in plants, they reduce atmospheric carbon dioxide into organic carbon sugars to feed both symbionts. Phycobionts (algae) produce sugar alcohols (ribitol, sorbitol, and erythritol), which are absorbed by the mycobiont (fungus). Cyanobionts produce glucose. Lichenized fungal cells can make the photobiont "leak" out the products of photosynthesis, where they can then be absorbed by the fungus.: 5
It appears many, probably the majority, of lichen also live in a symbiotic relationship with an order of basidiomycete yeasts called Cyphobasidiales. The absence of this third partner could explain why growing lichen in the laboratory is difficult. The yeast cells are responsible for the formation of the characteristic cortex of the lichen thallus, and could also be important for its shape.
The lichen combination of alga or cyanobacterium with a fungus has a very different form (morphology), physiology, and biochemistry than the component fungus, alga, or cyanobacterium growing by itself, naturally or in culture. The body (thallus) of most lichens is different from those of either the fungus or alga growing separately. When grown in the laboratory in the absence of its photobiont, a lichen fungus develops as a structureless, undifferentiated mass of fungal filaments (hyphae). If combined with its photobiont under appropriate conditions, its characteristic form associated with the photobiont emerges, in the process called morphogenesis. In a few remarkable cases, a single lichen fungus can develop into two very different lichen forms when associating with either a green algal or a cyanobacterial symbiont. Quite naturally, these alternative forms were at first considered to be different species, until they were found growing in a conjoined manner.
Evidence that lichens are examples of successful symbiosis is the fact that lichens can be found in almost every habitat and geographic area on the planet. Two species in two genera of green algae are found in over 35% of all lichens, but can only rarely be found living on their own outside of a lichen.
In a case where one fungal partner simultaneously had two green algae partners that outperform each other in different climates, this might indicate having more than one photosynthetic partner at the same time might enable the lichen to exist in a wider range of habitats and geographic locations.
At least one form of lichen, the North American beard-like lichens, are constituted of not two but three symbiotic partners: an ascomycetous fungus, a photosynthetic alga, and, unexpectedly, a basidiomycetous yeast.
Phycobionts can have a net output of sugars with only water vapor. The thallus must be saturated with liquid water for cyanobionts to photosynthesize.
Algae produce sugars that are absorbed by the fungus by diffusion into special fungal hyphae called appressoria or haustoria in contact with the wall of the algal cells. The appressoria or haustoria may produce a substance that increases permeability of the algal cell walls, and may penetrate the walls. The algae may contribute up to 80% of their sugar production to the fungus.
=== Ecology ===
Lichen associations may be examples of mutualism or commensalism, but the lichen relationship can be considered parasitic under circumstances where the photosynthetic partner can exist in nature independently of the fungal partner, but not vice versa. Photobiont cells are routinely destroyed in the course of nutrient exchange. The association continues because reproduction of the photobiont cells matches the rate at which they are destroyed. The fungus surrounds the algal cells, often enclosing them within complex fungal tissues unique to lichen associations. In many species the fungus penetrates the algal cell wall, forming penetration pegs (haustoria) similar to those produced by pathogenic fungi that feed on a host. Cyanobacteria in laboratory settings can grow faster when they are alone rather than when they are part of a lichen.
==== Miniature ecosystem and holobiont theory ====
Symbiosis in lichens is so well-balanced that lichens have been considered to be relatively self-contained miniature ecosystems in and of themselves. It is thought that lichens may be even more complex symbiotic systems that include non-photosynthetic bacterial communities performing other functions as partners in a holobiont.
Many lichens are very sensitive to environmental disturbances and can be used to cheaply assess air pollution, ozone depletion, and metal contamination. Lichens have been used in making dyes, perfumes (oakmoss), and in traditional medicines. A few lichen species are eaten by insects or larger animals, such as reindeer. Lichens are widely used as environmental indicators or bio-indicators. When air is very badly polluted with sulphur dioxide, there may be no lichens present; only some green algae can tolerate those conditions. If the air is clean, then shrubby, hairy and leafy lichens become abundant. A few lichen species can tolerate fairly high levels of pollution, and are commonly found in urban areas, on pavements, walls and tree bark. The most sensitive lichens are shrubby and leafy, while the most tolerant lichens are all crusty in appearance. Since industrialisation, many of the shrubby and leafy lichens such as Ramalina, Usnea and Lobaria species have very limited ranges, often being confined to the areas which have the cleanest air.
==== Lichenicolous fungi ====
Some fungi can only be found living on lichens as obligate parasites. These are referred to as lichenicolous fungi, and are a different species from the fungus living inside the lichen; thus they are not considered to be part of the lichen.
=== Reaction to water ===
Moisture makes the cortex become more transparent.: 4 This way, the algae can conduct photosynthesis when moisture is available, and is protected at other times. When the cortex is more transparent, the algae show more clearly and the lichen looks greener.
=== Metabolites, metabolite structures and bioactivity ===
Lichens can show intense antioxidant activity. Secondary metabolites are often deposited as crystals in the apoplast. Secondary metabolites are thought to play a role in preference for some substrates over others.
=== Growth rate ===
Lichens often have a regular but very slow growth rate of less than a millimeter per year.
In crustose lichens, the area along the margin is where the most active growth is taking place.: 159 Most crustose lichens grow only 1–2 mm in diameter per year.
=== Life span ===
Lichens may be long-lived, with some considered to be among the oldest living organisms. Lifespan is difficult to measure because what defines the "same" individual lichen is not precise. Lichens grow by vegetatively breaking off a piece, which may or may not be defined as the "same" lichen, and two lichens can merge, then becoming the "same" lichen. One specimen of Rhizocarpon geographicum on East Baffin Island has an estimated age of 9500 years. Thalli of Rhizocarpon geographicum and Rhizocarpon eupetraeoides/inarense in the central Brooks Range of northern Alaska have been given a maximum possible age of 10,000–11,500 years.
=== Response to environmental stress ===
Unlike simple dehydration in plants and animals, lichens may experience a complete loss of body water in dry periods. Lichens are capable of surviving extremely low levels of water content (poikilohydric).: 5–6 They quickly absorb water when it becomes available again, becoming soft and fleshy.
In tests, lichen survived and showed remarkable results on the adaptation capacity of photosynthetic activity within the simulation time of 34 days under Martian conditions in the Mars Simulation Laboratory (MSL) maintained by the German Aerospace Center (DLR).
The European Space Agency has discovered that lichens can survive unprotected in space. In an experiment led by Leopoldo Sancho from the Complutense University of Madrid, two species of lichen—Rhizocarpon geographicum and Rusavskia elegans—were sealed in a capsule and launched on a Russian Soyuz rocket 31 May 2005. Once in orbit, the capsules were opened and the lichens were directly exposed to the vacuum of space with its widely fluctuating temperatures and cosmic radiation. After 15 days, the lichens were brought back to earth and were found to be unchanged in their ability to photosynthesize.
== Reproduction and dispersal ==
=== Vegetative reproduction ===
Many lichens reproduce asexually, either by a piece breaking off and growing on its own (vegetative reproduction) or through the dispersal of diaspores containing a few algal cells surrounded by fungal cells. Because of the relative lack of differentiation in the thallus, the line between diaspore formation and vegetative reproduction is often blurred. Fruticose lichens can fragment, and new lichens can grow from the fragment (vegetative reproduction). Many lichens break up into fragments when they dry, dispersing themselves by wind action, to resume growth when moisture returns. Soredia (singular: "soredium") are small groups of algal cells surrounded by fungal filaments that form in structures called soralia, from which the soredia can be dispersed by wind. Isidia (singular: "isidium") are branched, spiny, elongated, outgrowths from the thallus that break off for mechanical dispersal. Lichen propagules (diaspores) typically contain cells from both partners, although the fungal components of so-called "fringe species" rely instead on algal cells dispersed by the "core species".
=== Sexual reproduction ===
Structures involved in reproduction often appear as discs, bumps, or squiggly lines on the surface of the thallus.: 4 Though it has been argued that sexual reproduction in photobionts is selected against, there is strong evidence that suggests meiotic activities (sexual reproduction) in Trebouxia. Many lichen fungi reproduce sexually like other fungi, producing spores formed by meiosis and fusion of gametes. Following dispersal, such fungal spores must meet with a compatible algal partner before a functional lichen can form.
Some lichen fungi belong to the phylum Basidiomycota (basidiolichens) and produce mushroom-like reproductive structures resembling those of their nonlichenized relatives.
Most lichen fungi belong to Ascomycetes (ascolichens). Among the ascolichens, spores are produced in spore-producing structures called ascomata. The most common types of ascomata are the apothecium (plural: apothecia) and perithecium (plural: perithecia).: 14 Apothecia are usually cups or plate-like discs located on the top surface of the lichen thallus. When apothecia are shaped like squiggly line segments instead of like discs, they are called lirellae.: 14 Perithecia are shaped like flasks that are immersed in the lichen thallus tissue, which has a small hole for the spores to escape the flask, and appear like black dots on the lichen surface.: 14
The three most common spore body types are raised discs called apothecia (singular: apothecium), bottle-like cups with a small hole at the top called perithecia (singular: perithecium), and pycnidia (singular: pycnidium), shaped like perithecia but without asci (an ascus is the structure that contains and releases the sexual spores in fungi of the Ascomycota).
The apothecium has a layer of exposed spore-producing cells called asci (singular: ascus), and is usually a different color from the thallus tissue.: 14 When the apothecium has an outer margin, the margin is called the exciple.: 14 When the exciple has a color similar to colored thallus tissue the apothecium or lichen is called lecanorine, meaning similar to members of the genus Lecanora.: 14 When the exciple is blackened like carbon it is called lecideine meaning similar to members of the genus Lecidea.: 14 When the margin is pale or colorless it is called biatorine.: 14
A "podetium" (plural: podetia) is a lichenized stalk-like structure of the fruiting body rising from the thallus, associated with some fungi that produce a fungal apothecium. Since it is part of the reproductive tissue, podetia are not considered part of the main body (thallus), but may be visually prominent. The podetium may be branched, and sometimes cup-like. They usually bear the fungal pycnidia or apothecia or both. Many lichens have apothecia that are visible to the naked eye.
Most lichens produce abundant sexual structures. Many species appear to disperse only by sexual spores. For example, the crustose lichens Graphis scripta and Ochrolechia parella produce no symbiotic vegetative propagules. Instead, the lichen-forming fungi of these species reproduce sexually by self-fertilization (i.e. they are homothallic). This breeding system may enable successful reproduction in harsh environments.
Mazaedia (singular: mazaedium) are apothecia shaped like a dressmaker's pin in pin lichens, where the fruiting body is a brown or black mass of loose ascospores enclosed by a cup-shaped exciple, which sits on top of a tiny stalk.: 15
== Taxonomy and classification ==
Lichens are classified by the fungal component. Lichen species are given the same scientific name (binomial name) as the fungus species in the lichen. Lichens are being integrated into the classification schemes for fungi. The alga bears its own scientific name, which bears no relationship to that of the lichen or fungus. There are about 20,000 identified lichen species, and taxonomists have estimated that the total number of lichen species (including those yet undiscovered) might be as high as 28,000. Nearly 20% of known fungal species are associated with lichens.
"Lichenized fungus" may refer to the entire lichen, or to just the fungus. This may cause confusion without context. A particular fungus species may form lichens with different algae species, giving rise to what appear to be different lichen species, but which are still classified (as of 2014) as the same lichen species.
Formerly, some lichen taxonomists placed lichens in their own division, the Mycophycophyta, but this practice is no longer accepted because the components belong to separate lineages. Neither the ascolichens nor the basidiolichens form monophyletic lineages in their respective fungal phyla, but they do form several major solely or primarily lichen-forming groups within each phylum. Even more unusual than basidiolichens is the fungus Geosiphon pyriforme, a member of the Glomeromycota that is unique in that it encloses a cyanobacterial symbiont inside its cells. Geosiphon is not usually considered to be a lichen, and its peculiar symbiosis was not recognized for many years. The genus is more closely allied to endomycorrhizal genera. Fungi from Verrucariales also form marine lichens with the brown algae Petroderma maculiforme, and have a symbiotic relationship with seaweed (such as rockweed) and Blidingia minima, where the algae are the dominant components. The fungi is thought to help the rockweeds to resist desiccation when exposed to air. In addition, lichens can also use yellow-green algae (Heterococcus) as their symbiotic partner.
Lichens independently emerged from fungi associating with algae and cyanobacteria multiple times throughout history.
=== Fungi ===
The fungal component of a lichen is called the mycobiont. The mycobiont may be an Ascomycete or Basidiomycete. The associated lichens are called either ascolichens or basidiolichens, respectively. Living as a symbiont in a lichen appears to be a successful way for a fungus to derive essential nutrients, since about 20% of all fungal species have acquired this mode of life.
Thalli produced by a given fungal symbiont with its differing partners may be similar, and the secondary metabolites identical, indicating that the fungus has the dominant role in determining the morphology of the lichen. But the same mycobiont with different photobionts may also produce very different growth forms. Lichens are known in which there is one fungus associated with two or even three algal species.
Although each lichen thallus generally appears homogeneous, some evidence seems to suggest that the fungal component may consist of more than one genetic individual of that species.
Two or more fungal species can interact to form the same lichen.
The following table lists the orders and families of fungi that include lichen-forming species.
=== Photobionts ===
The photosynthetic partner in a lichen is called a photobiont. The photobionts in lichens come from a variety of simple prokaryotic and eukaryotic organisms. In the majority of lichens the photobiont is a green alga (Chlorophyta) or a cyanobacterium. In some lichens both types are present; in such cases, the alga is typically the primary partner, with the cyanobacteria being located in cryptic pockets. Algal photobionts are called phycobionts, while cyanobacterial photobionts are called cyanobionts. About 90% of all known lichens have phycobionts, and about 10% have cyanobionts. Approximately 100 species of photosynthetic partners from 40 genera and five distinct classes (prokaryotic: Cyanophyceae; eukaryotic: Trebouxiophyceae, Phaeophyceae, Chlorophyceae) have been found to associate with the lichen-forming fungi.
Common algal photobionts are from the genera Trebouxia, Trentepohlia, Pseudotrebouxia, or Myrmecia. Trebouxia is the most common genus of green algae in lichens, occurring in about 40% of all lichens. "Trebouxioid" means either a photobiont that is in the genus Trebouxia, or resembles a member of that genus, and is therefore presumably a member of the class Trebouxiophyceae. The second most commonly represented green alga genus is Trentepohlia. Overall, about 100 species of eukaryotes are known to occur as photobionts in lichens. All the algae are probably able to exist independently in nature as well as in the lichen.
A "cyanolichen" is a lichen with a cyanobacterium as its main photosynthetic component (photobiont). Most cyanolichen are also ascolichens, but a few basidiolichen like Dictyonema and Acantholichen have cyanobacteria as their partner.
The most commonly occurring cyanobacterium genus is Nostoc. Other common cyanobacterium photobionts are from Scytonema. Many cyanolichens are small and black, and have limestone as the substrate. Another cyanolichen group, the jelly lichens of the genera Collema or Leptogium are gelatinous and live on moist soils. Another group of large and foliose species including Peltigera, Lobaria, and Degelia are grey-blue, especially when dampened or wet. Many of these characterize the Lobarion communities of higher rainfall areas in western Britain, e.g., in the Celtic rain forest. Strains of cyanobacteria found in various cyanolichens are often closely related to one another. They differ from the most closely related free-living strains.
The lichen association is a close symbiosis. It extends the ecological range of both partners but is not always obligatory for their growth and reproduction in natural environments, since many of the algal symbionts can live independently. A prominent example is the alga Trentepohlia, which forms orange-coloured populations on tree trunks and suitable rock faces. Lichen propagules (diaspores) typically contain cells from both partners, although the fungal components of so-called "fringe species" rely instead on algal cells dispersed by the "core species".
The same cyanobiont species can occur in association with different fungal species as lichen partners. The same phycobiont species can occur in association with different fungal species as lichen partners. More than one phycobiont may be present in a single thallus.
A single lichen may contain several algal genotypes. These multiple genotypes may better enable response to adaptation to environmental changes, and enable the lichen to inhabit a wider range of environments.
=== Controversy over classification method and species names ===
There are about 20,000 known lichen species. But what is meant by "species" is different from what is meant by biological species in plants, animals, or fungi, where being the same species implies that there is a common ancestral lineage. Because lichens are combinations of members of two or even three different biological kingdoms, these components must have a different ancestral lineage from each other. By convention, lichens are still called "species" anyway, and are classified according to the species of their fungus, not the species of the algae or cyanobacteria. Lichens are given the same scientific name (binomial name) as the fungus in them, which may cause some confusion. The alga bears its own scientific name, which has no relationship to the name of the lichen or fungus.
Depending on context, "lichenized fungus" may refer to the entire lichen, or to the fungus when it is in the lichen, which can be grown in culture in isolation from the algae or cyanobacteria. Some algae and cyanobacteria are found naturally living outside of the lichen. The fungal, algal, or cyanobacterial component of a lichen can be grown by itself in culture. When growing by themselves, the fungus, algae, or cyanobacteria have very different properties than those of the lichen. Lichen properties such as growth form, physiology, and biochemistry, are very different from the combination of the properties of the fungus and the algae or cyanobacteria.
The same fungus growing in combination with different algae or cyanobacteria, can produce lichens that are very different in most properties, meeting non-DNA criteria for being different "species". Historically, these different combinations were classified as different species. When the fungus is identified as being the same using modern DNA methods, these apparently different species get reclassified as the same species under the current (2014) convention for classification by fungal component. This has led to debate about this classification convention. These apparently different "species" have their own independent evolutionary history.
There is also debate as to the appropriateness of giving the same binomial name to the fungus, and to the lichen that combines that fungus with an alga or cyanobacterium (synecdoche). This is especially the case when combining the same fungus with different algae or cyanobacteria produces dramatically different lichen organisms, which would be considered different species by any measure other than the DNA of the fungal component. If the whole lichen produced by the same fungus growing in association with different algae or cyanobacteria, were to be classified as different "species", the number of "lichen species" would be greater.
=== Diversity ===
The largest number of lichenized fungi occur in the Ascomycota, with about 40% of species forming such an association. Some of these lichenized fungi occur in orders with nonlichenized fungi that live as saprotrophs or plant parasites (for example, the Leotiales, Dothideales, and Pezizales). Other lichen fungi occur in only five orders in which all members are engaged in this habit (Orders Graphidales, Gyalectales, Peltigerales, Pertusariales, and Teloschistales). Overall, about 98% of lichens have an ascomycetous mycobiont. Next to the Ascomycota, the largest number of lichenized fungi occur in the unassigned fungi imperfecti, a catch-all category for fungi whose sexual form of reproduction has never been observed. Comparatively few basidiomycetes are lichenized, but these include agarics, such as species of Lichenomphalia, clavarioid fungi, such as species of Multiclavula, and corticioid fungi, such as species of Dictyonema.
=== Identification methods ===
Lichen identification uses growth form, microscopy and reactions to chemical tests.
The outcome of the "Pd test" is called "Pd", which is also used as an abbreviation for the chemical used in the test, para-phenylenediamine. If putting a drop on a lichen turns an area bright yellow to orange, this helps identify it as belonging to either the genus Cladonia or Lecanora.
=== Evolution and paleontology ===
The fossil record for lichens is poor. The extreme habitats that lichens dominate, such as tundra, mountains, and deserts, are not ordinarily conducive to producing fossils. There are fossilized lichens embedded in amber. The fossilized Anzia is found in pieces of amber in northern Europe and dates back approximately 40 million years. Lichen fragments are also found in fossil leaf beds, such as Lobaria from Trinity County in northern California, US, dating back to the early to middle Miocene.
The oldest fossil lichen in which both symbiotic partners have been recovered is Winfrenatia, an early zygomycetous (Glomeromycotan) lichen symbiosis that may have involved controlled parasitism, is permineralized in the Rhynie Chert of Scotland, dating from early Early Devonian, about 400 million years ago. The slightly older fossil Spongiophyton has also been interpreted as a lichen on morphological and isotopic grounds, although the isotopic basis is decidedly shaky. It has been demonstrated that Silurian-Devonian fossils Nematothallus and Prototaxites were lichenized. Thus lichenized Ascomycota and Basidiomycota were a component of Early Silurian-Devonian terrestrial ecosystems. Newer research suggests that lichen evolved after the evolution of land plants.
The ancestral ecological state of both Ascomycota and Basidiomycota was probably saprobism, and independent lichenization events may have occurred multiple times. In 1995, Gargas and colleagues proposed that there were at least five independent origins of lichenization; three in the basidiomycetes and at least two in the Ascomycetes. Lutzoni et al. (2001) suggest lichenization probably evolved earlier and was followed by multiple independent losses. Some non-lichen-forming fungi may have secondarily lost the ability to form a lichen association. As a result, lichenization has been viewed as a highly successful nutritional strategy.
Lichenized Glomeromycota may extend well back into the Precambrian. Lichen-like fossils consisting of coccoid cells (cyanobacteria?) and thin filaments (mucoromycotinan Glomeromycota?) are permineralized in marine phosphorite of the Doushantuo Formation in southern China. These fossils are thought to be 551 to 635 million years old or Ediacaran. Ediacaran acritarchs also have many similarities with Glomeromycotan vesicles and spores. It has also been claimed that Ediacaran fossils including Dickinsonia, were lichens, although this claim is controversial. Endosymbiotic Glomeromycota comparable with living Geosiphon may extend back into the Proterozoic in the form of 1500 million year old Horodyskia and 2200 million year old Diskagma. Discovery of these fossils suggest that fungi developed symbiotic partnerships with photoautotrophs long before the evolution of vascular plants, though the Ediacaran lichen hypothesis is largely rejected due to an inappropriate definition of lichens based on taphonomy and substrate ecology. However, a 2019 study by the same scientist who rejected the Ediacaran lichen hypothesis, Nelsen, used new time-calibrated phylogenies to conclude that there is no evidence of lichen before the existence of vascular plants.
Lecanoromycetes, one of the most common classes of lichen-forming fungi, diverged from its ancestor, which may have also been lichen forming, around 258 million years ago, during the late Paleozoic period. However, the closely related clade Euritiomycetes appears to have become lichen-forming only 52 million years ago, during the early Cenozoic period.
== Ecology and interactions with environment ==
=== Substrates and habitats ===
Lichens grow on and in a wide range of substrates and habitats, including some of the most extreme conditions on earth. They are abundant growing on bark, leaves, and hanging from epiphyte branches in rain forests and in temperate woodland. They grow on bare rock, walls, gravestones, roofs, and exposed soil surfaces. They can survive in some of the most extreme environments on Earth: arctic tundra, hot dry deserts, rocky coasts, and toxic slag heaps. They can live inside solid rock, growing between the grains, and in the soil as part of a biological soil crust in arid habitats such as deserts. Some lichens do not grow on anything, living out their lives blowing about the environment.
When growing on mineral surfaces, some lichens slowly decompose their substrate by chemically degrading and physically disrupting the minerals, contributing to the process of weathering by which rocks are gradually turned into soil. While this contribution to weathering is usually benign, it can cause problems for artificial stone structures. For example, there is an ongoing lichen growth problem on Mount Rushmore National Memorial that requires the employment of mountain-climbing conservators to clean the monument.
Lichens are not parasites on the plants they grow on, but only use them as a substrate. The fungi of some lichen species may "take over" the algae of other lichen species. Lichens make their own food from their photosynthetic parts and by absorbing minerals from the environment. Lichens growing on leaves may have the appearance of being parasites on the leaves, but they are not. Some lichens in Diploschistes parasitise other lichens. Diploschistes muscorum starts its development in the tissue of a host Cladonia species.: 30 : 171
In the arctic tundra, lichens, together with mosses and liverworts, make up the majority of the ground cover, which helps insulate the ground and may provide forage for grazing animals. An example is "reindeer moss", which is a lichen, not a moss.
There are only two species of known permanently submerged lichens; Hydrothyria venosa is found in fresh water environments, and Verrucaria serpuloides is found in marine environments.
A crustose lichen that grows on rock is called a saxicolous lichen.: 159 Crustose lichens that grow on the rock are epilithic, and those that grow immersed inside rock, growing between the crystals with only their fruiting bodies exposed to the air, are called endolithic lichens.: 159 A crustose lichen that grows on bark is called a corticolous lichen.: 159 A lichen that grows on wood from which the bark has been stripped is called a lignicolous lichen. Lichens that grow immersed inside plant tissues are called endophloidic lichens or endophloidal lichens.: 159 Lichens that use leaves as substrates, whether the leaf is still on the tree or on the ground, are called epiphyllous or foliicolous. A terricolous lichen grows on the soil as a substrate. Many squamulose lichens are terricolous.: 159 Umbilicate lichens are foliose lichens that are attached to the substrate at only one point. A vagrant lichen is not attached to a substrate at all, and lives its life being blown around by the wind.
=== Lichens and soils ===
In addition to distinct physical mechanisms by which lichens break down raw stone, studies indicate lichens attack stone chemically, entering newly chelated minerals into the ecology. The substances exuded by lichens, known for their strong ability to bind and sequester metals, along with the common formation of new minerals, especially metal oxalates, and the traits of the substrates they alter, all highlight the important role lichens play in the process of chemical weathering. Over time, this activity creates new fertile soil from stone.
Lichens may be important in contributing nitrogen to soils in some deserts through being eaten, along with their rock substrate, by snails, which then defecate, putting the nitrogen into the soils. Lichens help bind and stabilize soil sand in dunes. In deserts and semi-arid areas, lichens are part of extensive, living biological soil crusts, essential for maintaining the soil structure.
=== Ecological interactions ===
Lichens are pioneer species, among the first living things to grow on bare rock or areas denuded of life by a disaster. Lichens may have to compete with plants for access to sunlight, but because of their small size and slow growth, they thrive in places where higher plants have difficulty growing. Lichens are often the first to settle in places lacking soil, constituting the sole vegetation in some extreme environments such as those found at high mountain elevations and at high latitudes. Some survive in the tough conditions of deserts, and others on frozen soil of the Arctic regions.
A major ecophysiological advantage of lichens is that they are poikilohydric (poikilo- variable, hydric- relating to water), meaning that though they have little control over the status of their hydration, they can tolerate irregular and extended periods of severe desiccation. Like some mosses, liverworts, ferns and a few resurrection plants, upon desiccation, lichens enter a metabolic suspension or stasis (known as cryptobiosis) in which the cells of the lichen symbionts are dehydrated to a degree that halts most biochemical activity. In this cryptobiotic state, lichens can survive wider extremes of temperature, radiation and drought in the harsh environments they often inhabit.
Lichens do not have roots and do not need to tap continuous reservoirs of water like most higher plants, thus they can grow in locations impossible for most plants, such as bare rock, sterile soil or sand, and various artificial structures such as walls, roofs, and monuments. Many lichens also grow as epiphytes (epi- on the surface, phyte- plant) on plants, particularly on the trunks and branches of trees. When growing on plants, lichens are not parasites; they do not consume any part of the plant nor poison it. Lichens produce allelopathic chemicals that inhibit the growth of mosses. Some ground-dwelling lichens, such as members of the subgenus Cladina (reindeer lichens), produce allelopathic chemicals that leach into the soil and inhibit the germination of seeds, spruce and other plants. Stability (that is, longevity) of their substrate is a major factor of lichen habitats. Most lichens grow on stable rock surfaces or the bark of old trees, but many others grow on soil and sand. In these latter cases, lichens are often an important part of soil stabilization; indeed, in some desert ecosystems, vascular (higher) plant seeds cannot become established except in places where lichen crusts stabilize the sand and help retain water.
Lichens may be eaten by some animals, such as reindeer, living in arctic regions. The larvae of a number of Lepidoptera species feed exclusively on lichens. These include common footman and marbled beauty. They are very low in protein and high in carbohydrates, making them unsuitable for some animals. The Northern flying squirrel uses it for nesting, food and winter water.
=== Effects of air pollution ===
If lichens are exposed to air pollutants at all times, without any deciduous parts, they are unable to avoid the accumulation of pollutants. Also lacking stomata and a cuticle, lichens may absorb aerosols and gases over the entire thallus surface from which they may readily diffuse to the photobiont layer. Because lichens do not possess roots, their primary source of most elements is the air, and therefore elemental levels in lichens often reflect the accumulated composition of ambient air. The processes by which atmospheric deposition occurs include fog and dew, gaseous absorption, and dry deposition. Consequently, environmental studies with lichens emphasize their feasibility as effective biomonitors of atmospheric quality.
Not all lichens are equally sensitive to air pollutants, so different lichen species show different levels of sensitivity to specific atmospheric pollutants. The sensitivity of a lichen to air pollution is directly related to the energy needs of the mycobiont, so that the stronger the dependency of the mycobiont on the photobiont, the more sensitive the lichen is to air pollution. Upon exposure to air pollution, the photobiont may use metabolic energy for repair of its cellular structures that would otherwise be used for maintenance of its photosynthetic activity, therefore leaving less metabolic energy available for the mycobiont. The alteration of the balance between the photobiont and mycobiont can lead to the breakdown of the symbiotic association. Therefore, lichen decline may result not only from the accumulation of toxic substances, but also from altered nutrient supplies that favor one symbiont over the other.
This interaction between lichens and air pollution has been used as a means of monitoring air quality since 1859, with more systematic methods developed by William Nylander in 1866.. The use of lichen to produce zonal maps of pollution in cities was further developed by British lichenologist Oliver Gilbert, and then by Francis Rose. This resulted in a scale of lichen indicative of different levels of pollution, which became known as the 'Hawksworth and Rose' scale. Variations of this are still used today, with standardized methodology available.
== Human use ==
=== Food ===
Lichens are eaten by many different cultures across the world. Although some lichens are only eaten in times of famine, others are a staple food or even a delicacy. Two obstacles are often encountered when eating lichens: lichen polysaccharides are generally indigestible to humans, and lichens usually contain mildly toxic secondary compounds that should be removed before eating. Very few lichens are poisonous, but those high in vulpinic acid or usnic acid are toxic. Most poisonous lichens are yellow.
In the past, Iceland moss (Cetraria islandica) was an important source of food for humans in northern Europe, and was cooked as a bread, porridge, pudding, soup, or salad. Bryoria fremontii (edible horsehair lichen) was an important food in parts of North America, where it was usually pitcooked. Northern peoples in North America and Siberia traditionally eat the partially digested reindeer lichen (Cladina spp.) after they remove it from the rumen of caribou or reindeer that have been killed. Rock tripe (Umbilicaria spp. and Lasalia spp.) is a lichen that has frequently been used as an emergency food in North America, and one species, Umbilicaria esculenta, (iwatake in Japanese) is used in a variety of traditional Korean and Japanese foods.
=== Lichenometry ===
Lichenometry is a technique used to determine the age of exposed rock surfaces based on the size of lichen thalli. Introduced by Beschel in the 1950s, the technique has found many applications. it is used in archaeology, palaeontology, and geomorphology. It uses the presumed regular but slow rate of lichen growth to determine the age of exposed rock.: 9 Measuring the diameter (or other size measurement) of the largest lichen of a species on a rock surface indicates the length of time since the rock surface was first exposed. Lichen can be preserved on old rock faces for up to 10,000 years, providing the maximum age limit of the technique, though it is most accurate (within 10% error) when applied to surfaces that have been exposed for less than 1,000 years. Lichenometry is especially useful for dating surfaces less than 500 years old, as radiocarbon dating techniques are less accurate over this period. The lichens most commonly used for lichenometry are those of the genera Rhizocarpon (e.g. the species Rhizocarpon geographicum, map lichen) and Xanthoria.
=== Biodegradation ===
Lichens have been shown to degrade polyester resins, as can be seen in archaeological sites in the Roman city of Baelo Claudia in Spain. Lichens can accumulate several environmental pollutants such as lead, copper, and radionuclides. Some species of lichen, such as Parmelia sulcata (called a hammered shield lichen, among other names) and Lobaria pulmonaria (lung lichen), and many in the Cladonia genus, have been shown to produce serine proteases capable of the degradation of pathogenic forms of prion protein (PrP), which may be useful in treating contaminated environmental reservoirs.
=== Dyes ===
Many lichens produce secondary compounds, including pigments that reduce harmful amounts of sunlight and powerful toxins that deter herbivores or kill bacteria. These compounds are very useful for lichen identification, and have had economic importance as dyes such as cudbear or primitive antibiotics.
A pH indicator (which can indicate acidic or basic substances) called litmus is a dye extracted from the lichen Roccella tinctoria ("dyer's weed") by boiling. It gives its name to the well-known litmus test.
Traditional dyes of the Scottish Highlands for Harris tweed and other traditional cloths were made from lichens, including the orange Xanthoria parietina ("common orange lichen") and the grey foliaceous Parmelia saxatilis common on rocks and known colloquially as "crottle".
There are reports dating almost 2,000 years old of lichens being used to make purple and red dyes. Of great historical and commercial significance are lichens belonging to the family Roccellaceae, commonly called orchella weed or orchil. Orcein and other lichen dyes have largely been replaced by synthetic versions.
=== Traditional medicine and research ===
Historically, in traditional medicine of Europe, Lobaria pulmonaria was collected in large quantities as "lungwort", due to its lung-like appearance (the "doctrine of signatures" suggesting that herbs can treat body parts that they physically resemble).Similarly, Peltigera leucophlebia ("ruffled freckled pelt") was used as a supposed cure for thrush, due to the resemblance of its cephalodia to the appearance of the disease.
Lichens produce metabolites being researched for their potential therapeutic or diagnostic value. Some metabolites produced by lichens are structurally and functionally similar to broad-spectrum antibiotics while few are associated respectively to antiseptic similarities. Usnic acid is the most commonly studied metabolite produced by lichens. It is also under research as a bactericidal agent against Escherichia coli and Staphylococcus aureus.
=== Aesthetic appeal ===
Colonies of lichens may be spectacular in appearance, dominating the surface of the visual landscape as part of the aesthetic appeal to visitors of Yosemite National Park, Sequoia National Park, and the Bay of Fires.: 2 Orange and yellow lichens add to the ambience of desert trees, tundras, and rocky seashores. Intricate webs of lichens hanging from tree branches add a mysterious aspect to forests. Fruticose lichens are used in model railroading and other modeling hobbies as a material for making miniature trees and shrubs.
=== In literature ===
In early Midrashic literature, the Hebrew word "vayilafeth" in Ruth 3:8 is explained as referring to Ruth entwining herself around Boaz like lichen. The 10th century Arab physician Al-Tamimi mentions lichens dissolved in vinegar and rose water being used in his day for the treatment of skin diseases and rashes.
The plot of John Wyndham's science fiction novel Trouble with Lichen revolves around an anti-aging chemical extracted from a lichen.
== History ==
Although lichens had been recognized as organisms for quite some time, it was not until 1867, when Swiss botanist Simon Schwendener proposed his dual theory of lichens, that lichens are a combination of fungi with algae or cyanobacteria, whereby the true nature of the lichen association began to emerge. Schwendener's hypothesis, which at the time lacked experimental evidence, arose from his extensive analysis of the anatomy and development in lichens, algae, and fungi using a light microscope. Many of the leading lichenologists at the time, such as James Crombie and Nylander, rejected Schwendener's hypothesis because the consensus was that all living organisms were autonomous.
Other prominent biologists, such as Heinrich Anton de Bary, Albert Bernhard Frank, Beatrix Potter, Melchior Treub and Hermann Hellriegel, were not so quick to reject Schwendener's ideas and the concept soon spread into other areas of study, such as microbial, plant, animal and human pathogens. When the complex relationships between pathogenic microorganisms and their hosts were finally identified, Schwendener's hypothesis began to gain popularity. Further experimental proof of the dual nature of lichens was obtained when Eugen Thomas published his results in 1939 on the first successful re-synthesis experiment.
In the 2010s, a new facet of the fungi–algae partnership was discovered. Toby Spribille and colleagues found that many types of lichen that were long thought to be ascomycete–algae pairs were actually ascomycete–basidiomycete–algae trios. The third symbiotic partner in many lichens is a basidiomycete yeast.
== See also ==
Lichenology
Lichens and nitrogen cycling
Mycophycobiosis - a symbiosis where a fungus lives in the macroscopic thallus of fresh water and marine algae; technically not a lichen but a similar phenomenon where fungi and algae are in symbiosis
== Notes ==
== References == | A lichen ( LY-kən, UK also LITCH-ən) is a symbiosis of algae or cyanobacteria living among filaments of multiple fungi species, along with a yeast embedded in the cortex or "skin", in a mutualistic relationship. Lichens are important actors in nutrient cycling and act as producers which many higher trophic feeders feed on, such as reindeer, gastropods, nematodes, mites, and springtails. Lichens have properties different from those of their component organisms. They come in many colors, sizes, and forms and are sometimes plant-like, but are not plants. They may have tiny, leafless branches (fruticose); flat leaf-like structures (foliose); grow crust-like, adhering tightly to a surface (substrate) like a thick coat of paint (crustose); have a powder-like appearance (leprose); or other growth forms.
A macrolichen is a lichen that is either bush-like or leafy; all other lichens are termed microlichens. Here, "macro" and "micro" do not refer to size, but to the growth form. Common names for lichens may contain the word moss (e.g., "reindeer moss", "Iceland moss"), and lichens may superficially look like and grow with mosses, but they are not closely related to mosses or any plant.: 3 Lichens do not have roots that absorb water and nutrients as plants do,: 2 but like plants, they produce their own nutrition by photosynthesis. When they grow on plants, they do not live as parasites, but instead use the plant's surface as a substrate.
Lichens occur from sea level to high alpine elevations, in many environmental conditions, and can grow on almost any surface. They are abundant growing on bark, leaves, mosses, or other lichens and hanging from branches "living on thin air" (epiphytes) in rainforests and in temperate woodland. They grow on rock, walls, gravestones, roofs, exposed soil surfaces, rubber, bones, and in the soil as part of biological soil crusts. Various lichens have adapted to survive in some of the most extreme environments on Earth: arctic tundra, hot dry deserts, rocky coasts, and toxic slag heaps. They can even live inside solid rock, growing between the grains (endolithic).
There are about 20,000 known species. Some lichens have lost the ability to reproduce sexually, yet continue to speciate. They can be seen as being relatively self-contained miniature ecosystems, where the fungi, algae, or cyanobacteria have the potential to engage with other microorganisms in a functioning system that may evolve as an even more complex composite organism. Lichens may be long-lived, with some considered to be among the oldest living things. They are among the first living things to grow on fresh rock exposed after an event such as a landslide. The long life-span and slow and regular growth rate of some species can be used to date events (lichenometry). Lichens are a keystone species in many ecosystems and benefit trees and birds. | 22 |
308 | lichen | Lichen (disambiguation) (wikipedia) | Lichen is a type of symbiotic organism.
Lichen may also refer to:
== Arts, entertainment, and media ==
Lichens (musician), Robert Lowe's solo musical project
"Lichen", the nickname for an untitled song by Aphex Twin from the album Selected Ambient Works Volume II
== Biology ==
Asphodelus albus, a herbaceous perennial plant sometimes called white lichen
Lichen planus, an inflammatory disease
Lichen sclerosus, a skin disease
Lichen simplex chronicus, a skin disease
== Places ==
Licheń Stary, a village in central Poland
Sanctuary of Our Lady of Licheń, a large church at Licheń Stary
Licheń, Lubusz Voivodeship, a village in western Poland
== See also ==
All pages with titles containing Lichen
Li Chen (disambiguation)
Lich, an undead creature
Lichen Lake (disambiguation)
Lycan (disambiguation) | Lichen is a type of symbiotic organism.
Lichen may also refer to: | 1 |
309 | apotheosis | Apotheose (wiktionary) | From Ancient Greek ἀποθέωσις (apothéōsis).
IPA(key): /apoteˈoːzə/
Apotheose f (genitive Apotheose, plural Apotheosen)
apotheosis
apotheotisch
Apotheose on the German Wikipedia.Wikipedia de
“Apotheose” in Duden online | From Ancient Greek ἀποθέωσις (apothéōsis).
IPA(key): /apoteˈoːzə/
Apotheose f (genitive Apotheose, plural Apotheosen)
apotheosis
apotheotisch
Apotheose on the German Wikipedia.Wikipedia de
“Apotheose” in Duden online | 6 |
310 | apotheosis | apotheose (wiktionary) | apotheose (third-person singular simple present apotheoses, present participle apotheosing, simple past and past participle apotheosed)
(transitive) Synonym of apotheosize
Ultimately from Ancient Greek ἀποθέωσις (apothéōsis). This etymology is incomplete. You can help Wiktionary by elaborating on the origins of this term.
IPA(key): /ˌaː.poː.teːˈoː.zə/
Hyphenation: apo‧the‧o‧se
Rhymes: -oːzə
apotheose f (plural apotheosen)
apotheosis
apotheōse
ablative singular of apotheōsis | apotheose (third-person singular simple present apotheoses, present participle apotheosing, simple past and past participle apotheosed)
(transitive) Synonym of apotheosize
Ultimately from Ancient Greek ἀποθέωσις (apothéōsis). This etymology is incomplete. You can help Wiktionary by elaborating on the origins of this term.
IPA(key): /ˌaː.poː.teːˈoː.zə/
Hyphenation: apo‧the‧o‧se
Rhymes: -oːzə
apotheose f (plural apotheosen)
apotheosis
apotheōse
ablative singular of apotheōsis | 11 |
311 | apotheosis | apotheosis (wiktionary) | Borrowed from Latin apotheōsis, from Ancient Greek ἀποθέωσις (apothéōsis), from verb ἀποθεόω (apotheóō, “deify”) (factitive verb formed from θεός (theós, “God”) with intensive prefix ἀπο- (apo-)) + -σις (-sis, “forms noun of action”). By surface analysis, apo- + theo- + -sis.
(UK) IPA(key): /əˌpɒθ.iːˈəʊ.sɪs/
(US) IPA(key): /əˌpɑ.θiˈoʊ.sɪs/
Rhymes: -əʊsɪs
apotheosis (countable and uncountable, plural apotheoses)
The fact or action of becoming or making into a god; deification.
Synonyms: deification, (Mormonism) exaltation
Glorification, exaltation; crediting someone or something with extraordinary power or status.
Synonyms: exaltation, glorification
1974, Per Lord Hailsham, Smedleys Ltd v Breed [1974]2 All ER 21(HL) at 24:
A glorified example or ideal; the apex or pinnacle (of a concept or belief).
Synonyms: apex, paragon
The best moment or highest point in the development of something, for example of a life or career; the apex, culmination, or climax (of a development).
Synonyms: apex, climax, culmination, peak, pinnacle
(loosely) Release from earthly life, ascension to heaven; death.
Synonym: death
(psychology) The latent entity that mediates between a person's psyche and their thoughts. The id, ego and superego in Freudian Psychology are examples of this.
apotheosize
apotheotic
apoth. (abbreviation)
Borrowed from Ancient Greek ἀποθέωσις (apothéōsis), from verb ἀποθεόω (apotheóō, “deify”) (factitive verb formed from θεός (theós, “God”) with intensive prefix ἀπο- (apo-)).
(Classical Latin) IPA(key): /a.po.tʰeˈoː.sis/, [äpɔt̪ʰeˈoːs̠ɪs̠]
(modern Italianate Ecclesiastical) IPA(key): /a.po.teˈo.sis/, [äpot̪eˈɔːs̬is]
apotheōsis f (genitive apotheōsis); third declension
apotheosis, deification
Third-declension noun (i-stem).
“apotheosis”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
apotheosis in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.
“apotheosis”, in Harry Thurston Peck, editor (1898), Harper's Dictionary of Classical Antiquities, New York: Harper & Brothers
“apotheosis”, in William Smith et al., editor (1890), A Dictionary of Greek and Roman Antiquities, London: William Wayte. G. E. Marindin | Borrowed from Latin apotheōsis, from Ancient Greek ἀποθέωσις (apothéōsis), from verb ἀποθεόω (apotheóō, “deify”) (factitive verb formed from θεός (theós, “God”) with intensive prefix ἀπο- (apo-)) + -σις (-sis, “forms noun of action”). By surface analysis, apo- + theo- + -sis.
(UK) IPA(key): /əˌpɒθ.iːˈəʊ.sɪs/
(US) IPA(key): /əˌpɑ.θiˈoʊ.sɪs/
Rhymes: -əʊsɪs
apotheosis (countable and uncountable, plural apotheoses)
The fact or action of becoming or making into a god; deification.
Synonyms: deification, (Mormonism) exaltation
Glorification, exaltation; crediting someone or something with extraordinary power or status.
Synonyms: exaltation, glorification
1974, Per Lord Hailsham, Smedleys Ltd v Breed [1974]2 All ER 21(HL) at 24:
A glorified example or ideal; the apex or pinnacle (of a concept or belief).
Synonyms: apex, paragon
The best moment or highest point in the development of something, for example of a life or career; the apex, culmination, or climax (of a development).
Synonyms: apex, climax, culmination, peak, pinnacle
(loosely) Release from earthly life, ascension to heaven; death.
Synonym: death
(psychology) The latent entity that mediates between a person's psyche and their thoughts. The id, ego and superego in Freudian Psychology are examples of this.
apotheosize
apotheotic
apoth. (abbreviation)
Borrowed from Ancient Greek ἀποθέωσις (apothéōsis), from verb ἀποθεόω (apotheóō, “deify”) (factitive verb formed from θεός (theós, “God”) with intensive prefix ἀπο- (apo-)).
(Classical Latin) IPA(key): /a.po.tʰeˈoː.sis/, [äpɔt̪ʰeˈoːs̠ɪs̠]
(modern Italianate Ecclesiastical) IPA(key): /a.po.teˈo.sis/, [äpot̪eˈɔːs̬is]
apotheōsis f (genitive apotheōsis); third declension
apotheosis, deification
Third-declension noun (i-stem).
“apotheosis”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
apotheosis in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.
“apotheosis”, in Harry Thurston Peck, editor (1898), Harper's Dictionary of Classical Antiquities, New York: Harper & Brothers
“apotheosis”, in William Smith et al., editor (1890), A Dictionary of Greek and Roman Antiquities, London: William Wayte. G. E. Marindin | 36 |
312 | apotheosis | Apotheosis (wikipedia) | Apotheosis (from Ancient Greek ἀποθέωσις (apothéōsis), from ἀποθεόω/ἀποθεῶ (apotheóō/apotheô) 'to deify'), also called divinization or deification (from Latin deificatio 'making divine'), is the glorification of a subject to divine levels and, commonly, the treatment of a human being, any other living thing, or an abstract idea in the likeness of a deity.
The original sense of apotheosis relates to religion and is the subject of many works of art. Figuratively "apotheosis" may be used in almost any context for "the deification, glorification, or exaltation of a principle, practice, etc.", so normally attached to an abstraction of some sort.
In religion, apotheosis was a feature of many religions in the ancient world, and some that are active today. It requires a belief that there is a possibility of newly-created gods, so a polytheistic belief system. The major modern religions of Christianity, Islam, and Judaism do not allow for this, though many recognise minor sacred categories such as saints (created by a process called canonization). In Christian theology there is a concept of the faithful becoming god-like, called divinization or in Eastern Christianity theosis. In Hinduism there is some scope for new deities. A human may be deified by becoming regarded as an avatar of an established deity, usually a major one, or by being regarded as a new, independent, deity (usually a minor one), or some mixture of the two.
In art, an apotheosis scene typically shows the subject in the heavens or rising towards them, often accompanied by a number of angels, putti, personifications of virtues, or similar figures. Especially from Baroque art onwards, apotheosis scenes may depict rulers, generals or artists purely as an honorific metaphor; in many cases the "religious" context is classical Greco-Roman pagan religion, as in The Apotheosis of Voltaire, featuring Apollo. The Apotheosis of Washington (1865), high up in the dome of the United States Capitol Building, is another example. Personifications of places or abstractions are also showed receiving an apotheosis. The typical composition was suitable for placement on ceilings or inside domes.
== Ancient Near East ==
Before the Hellenistic period, imperial cults were known in Ancient Egypt (pharaohs) and Mesopotamia (from Naram-Sin through Hammurabi). In the New Kingdom of Egypt, all deceased pharaohs were deified as the god Osiris, having been identified as Horus while on the throne, and sometimes referred to as the "son" of various other deities.
The architect Imhotep was deified after his death, though the process seems to have been gradual, taking well over a thousand years, by which time he had become associated primarily with medicine. About a dozen non-royal ancient Egyptians became regarded as deities.
== Ancient Greece ==
Greek mythology and its Roman equivalent have many figures who were born as humans but became gods, for example Hercules. They are typically made divine by one of the main deities, the Twelve Olympians. In the Roman story Cupid and Psyche, Zeus gives the ambrosia of the gods to the mortal Psyche, transforming her into a goddess herself. In the case of the Hellenistic queen Berenice II of Egypt, herself deified like other rulers of the Ptolemaic dynasty, the court propagated a myth that her hair, cut off to fulfill a vow, had its own apotheosis before becoming the Coma Berenices, a group of stars that still bear her name.
From at least the Geometric period of the ninth century BC, the long-deceased heroes linked with founding myths of Greek sites were accorded chthonic rites in their heroon, or "hero-temple".
In the Greek world, the first leader who accorded himself divine honours was Philip II of Macedon. At his wedding to his sixth wife, Philip's enthroned image was carried in procession among the Olympian gods; "his example at Aigai became a custom, passing to the Macedonian kings who were later worshipped in Greek Asia, from them to Julius Caesar and so to the emperors of Rome". Such Hellenistic state leaders might be raised to a status equal to the gods before death (e.g., Alexander the Great) or afterwards (e.g., members of the Ptolemaic dynasty). A heroic cult status similar to apotheosis was also an honour given to a few revered artists of the distant past, notably Homer.
Archaic and Classical Greek hero-cults became primarily civic, extended from their familial origins, in the sixth century; by the fifth century none of the worshipers based their authority by tracing descent back to the hero, with the exception of some families who inherited particular priestly cults, such as the Eumolpides (descended from Eumolpus) of the Eleusinian mysteries, and some inherited priesthoods at oracle sites.
The Greek hero cults can be distinguished on the other hand from the Roman cult of dead emperors, because the hero was not thought of as having ascended to Olympus or become a god: he was beneath the earth, and his power purely local. For this reason, hero cults were chthonic in nature, and their rituals more closely resembled those for Hecate and Persephone than those for Zeus and Apollo. Two exceptions were Heracles and Asclepius, who might be honoured as either gods or heroes, sometimes by chthonic night-time rites and sacrifice on the following day. One god considered as a hero to mankind is Prometheus, who secretly stole fire from Mount Olympus and introduced it to mankind.
== Ancient Rome ==
Up to the end of the Republic, the god Quirinus was the only one the Romans accepted as having undergone apotheosis, for his identification/syncretism with Romulus (see Euhemerism). Subsequently, apotheosis in ancient Rome was a process whereby a deceased ruler was recognized as divine by his successor, usually also by a decree of the Senate and popular consent. The first of these cases was the posthumous deification of the last Roman dictator Julius Caesar in 42 BC by his adopted son, the triumvir Caesar Octavian. In addition to showing respect, often the present ruler deified a popular predecessor to legitimize himself and gain popularity with the people.
A vote in the Roman Senate, in the later Empire confirming an imperial decree, was the normal official process, but this sometimes followed a period with the unofficial use of deific language or imagery for the individual, often done rather discreetly within the imperial circle. There was then a public ceremony, called a consecratio, including the release of an eagle which flew high, representing the ascent of the deified person's soul to heaven. Imagery featuring the ascent, sometimes using a chariot, was common on coins and in other art.
The largest and most famous example in art is a relief on the base of the Column of Antoninus Pius (d. 161), showing the emperor and his wife Faustina the Elder (d. c. 140) being carried up by a much larger winged figure, described as representing "Eternity", as personifications of "Roma" and the Campus Martius sit below, and eagles fly above. The imperial couple are represented as Jupiter and Juno.
The historian Dio Cassius, who says he was present, gives a detailed description of the large and lavish public consecratio of Pertinax, emperor for three months in 193, ordered by Septimius Severus.
At the height of the imperial cult during the Roman Empire, sometimes the emperor's deceased loved ones—heirs, empresses, or lovers, as Hadrian's Antinous—were deified as well. Deified people were awarded posthumously the title Divus (Diva if women) to their names to signify their divinity. Traditional Roman religion distinguished between a deus (god) and a divus (a mortal who became divine or deified), though not consistently. Temples and columns were erected to provide a space for worship.
The imperial cult was mainly popular in the provinces, especially in the Eastern Empire, where many cultures were well-used to deified rulers, and less popular in Rome itself, and among traditionalists and intellectuals. Some privately (and cautiously) ridiculed the apotheosis of inept and feeble emperors, as in the satire The Pumpkinification of (the Divine) Claudius, usually attributed to Seneca.
== Asia ==
Numerous mortals have been deified into the Taoist pantheon, such as Guan Yu, Iron-crutch Li and Fan Kuai. Song Dynasty General Yue Fei was deified during the Ming Dynasty and is considered by some practitioners to be one of the three highest-ranking heavenly generals. The Ming dynasty epic Investiture of the Gods deals heavily with deification legends.
In the complicated and variable conceptions of deity in Buddhism, the achievement of Buddhahood may be regarded as an achievable goal for the faithful, and many significant deities are considered to have begun as normal humans, from Gautama Buddha himself downwards. Most of these are seen as avatars or re-births of earlier figures.
Some significant Hindu deities, in particular Rama, were also born as humans; he is seen as an avatar of Vishnu. In more modern times, Swaminarayan is an undoubted and well-documented historical figure (1781–1830), who is regarded by some Hindus as an avatar of Krishna, himself another avatar of Vishnu, or as being a still more elevated deity. Bharat Mata ("Mother India") began as a national personification devised by a group of Bengali intellectuals in the late 19th century, but now receives some worship.
Various Hindu and Buddhist rulers in the past have been represented as deities, especially after death, from India to Indonesia. Jayavarman VII, King of the Khmer Empire (r. 1181–1218) the first Buddhist king of Cambodia, had his own features used for the many statues of Buddha/Avalokitesvara he erected.
The extreme personality cult instituted by the founder of North Korea, Kim Il-Sung, has been said to represent a deification, though the state is avowedly atheist.
== Christianity ==
Instead of the word "apotheosis", Christian theology uses in English the words "deification" or "divinization" or the Greek word "theosis". Pre-Reformation and mainstream theology, in both East and West, views Jesus Christ as the preexisting God who undertook mortal existence, not as a mortal being who attained divinity (a view known as adoptionism). It holds that he has made it possible for human beings to be raised to the level of sharing the divine nature as 2 Peter 1:4 states that he became human to make humans "partakers of the divine nature". In John 10:34, Jesus referenced Psalm 82:6 when he stated "Is it not written in your Law, I have said you are gods?" Other authors stated: "For this is why the Word became man, and the Son of God became the Son of man: so that man, by entering into communion with the Word and thus receiving divine sonship, might become a son of God." "For He was made man that we might be made God." "The only-begotten Son of God, wanting to make us sharers in his divinity, assumed our nature, so that he, made man, might make men gods."
Accusations of self deification to some degree may have been placed upon heretical groups such as the Waldensians.
The Westminster Dictionary of Christian Theology, authored by Anglican Priest Alan Richardson, contains the following in an article titled "Deification":
Deification (Greek theosis) is for Orthodoxy the goal of every Christian. Man, according to the Bible, is 'made in the image and likeness of God'. ... It is possible for man to become like God, to become deified, to become god by grace. This doctrine is based on many passages of both OT and NT (e.g. Ps. 82 (81).6; II Peter 1.4), and it is essentially the teaching both of St Paul, though he tends to use the language of filial adoption (cf. Rom. 8.9–17; Gal. 4.5–7), and the Fourth Gospel (cf. 17.21–23).
The language of II Peter is taken up by St Irenaeus, in his famous phrase, 'if the Word has been made man, it is so that men may be made gods' (Adv. Haer V, Pref.), and becomes the standard in Greek theology. In the fourth century, St. Athanasius repeats Irenaeus almost word for word, and in the fifth century, St. Cyril of Alexandria says that we shall become sons 'by participation' (Greek methexis). Deification is the central idea in the spirituality of St. Maximus the Confessor, for whom the doctrine is the corollary of the Incarnation: 'Deification, briefly, is the encompassing and fulfillment of all times and ages', ... and St. Symeon the New Theologian at the end of the tenth century writes, 'He who is God by nature converses with those whom he has made gods by grace, as a friend converses with his friends, face to face.'
=== Roman Catholic Church ===
The Roman Catholic Church does not use the term "apotheosis" in its theology. Corresponding to the Greek word theosis are the Latin-derived words "divinization" and "deification" used in the parts of the Catholic Church that are of Latin tradition. The concept has been given less prominence in Western theology than in that of the Eastern Catholic Churches, but is present in the Latin Church's liturgical prayers, such as that of the deacon or priest when pouring wine and a little water into the chalice: "By the mystery of this water and wine may we come to share in the divinity of Christ who humbled himself to share in our humanity."
Catholic theology stresses the concept of supernatural life, "a new creation and elevation, a rebirth, it is a participation in and partaking of the divine nature" (cf. 2 Peter 1:4). In Catholic teaching there is a vital distinction between natural life and supernatural life, the latter being "the life that God, in an act of love, freely gives to human beings to elevate them above their natural lives" and which they receive through prayer and the sacraments; indeed the Catholic Church sees human existence as having as its whole purpose the acquisition, preservation and intensification of this supernatural life.
Despite the theological differences, in Catholic church art depictions of the Assumption of the Virgin Mary in art and the Ascension of Jesus in Christian art share many similarities in composition to apotheosis subjects, as do many images of saints being raised to heaven. These last may use "apotheosis" in their modern titles. Early examples were often of the founders of religious orders, later canonized, with those of Saint Ignatius Loyola in the Church of the Gesù (Andrea Pozzo, 1691–1694, to the side of the nave cupola) and Saint Dominic in Santi Domenico e Sisto (1674–1675) two examples in Rome.
The Allegory of Divine Providence and Barberini Power by Pietro da Cortona (1630s) celebrated Pope Urban VIII and his family, combining heraldic symbols including the crossed keys of the Papacy and giant bees representing the Barberini family with personifications.
=== Eastern Orthodox Church ===
=== The Church of Jesus Christ of Latter-day Saints ===
The Church of Jesus Christ of Latter-day Saints (Mormons), believes in apotheosis along the lines of the Christian tradition of divinization or deification but refers to it as exaltation, or eternal life, and considers it to be accomplished by "sanctification". They believe that people may live with God throughout eternity in families and eventually become gods themselves but remain subordinate to God the Father, Jesus Christ, and the Holy Spirit. While the primary focus of the LDS Church is on Jesus of Nazareth and his atoning sacrifice for man, Latter-day Saints believe that one purpose for Christ's mission and for his atonement is the exaltation or Christian deification of man. The third Article of Faith of The Church of Jesus Christ of Latter-day Saints states that all men may be saved from sin by the atonement of Jesus Christ, and LDS Gospel Doctrine (as published) states that all men will be saved and will be resurrected from death. However, only those who are sufficiently obedient and accept the atonement and the grace and mercy of Jesus Christ before the resurrection and final judgment will be "exalted" and receive a literal Christian deification.
A quote often attributed to the early Church leader Lorenzo Snow in 1837, is "As man now is, God once was: As God now is, man may be." The teaching was taught first by Joseph Smith while he was pointing to John 5:19 in the New Testament; he said that "God himself, the Father of us all, dwelt on an earth, the same as Jesus Christ himself did." Many scholars also have discussed the correlation between Latter-day Saint belief in exaltation and the ancient Christian theosis, or deification, as set forth by early Church Fathers. Several Latter-day Saint and gentile historians specializing in studies of the early Christian Church also claim that the Latter-day Saint belief in eternal progression is more similar to the ancient Christian deification as set forth in numerous patristic writings of the 1st to 4th centuries AD than the beliefs of any other modern faith group of the Christian tradition.
Members of the Church believe that the original Christian belief in man's divine potential gradually lost its meaning and importance in the centuries after the death of the apostles, as doctrinal changes by post-apostolic theologians caused Christians to lose sight of the true nature of God and his purpose for creating humanity. The concept of God's nature that was eventually accepted as Christian doctrine in the 4th century set divinity apart from humanity by defining the Godhead as three persons sharing a common divine substance. That classification of God in terms of a substance is not found in scripture but, in many aspects, mirrored the Greek metaphysical philosophies that are known to have influenced the thinking of Church Fathers. Latter-day Saints teach that by modern revelation, God restored the knowledge that he is the literal father of our spirits (Hebrews 12:9) and that the Biblical references to God creating mankind in his image and likeness are in no way allegorical. As such, Mormons assert that as the literal offspring of God the Father (Acts 17:28–29), humans have the potential to be heirs of his glory and co-heirs with Christ (Romans 8:16–17). The glory, Mormons believe, lies not in God's substance but in his intelligence: in other words, light and truth (Doctrine and Covenants 93:36). Thus, the purpose of humans is to grow and progress to become like the Father in Heaven. Mortality is seen as a crucial step in the process in which God's spirit children gain a body, which, though formed in the image of the Father's body, is subject to pain, illness, temptation, and death. The purpose of this earth life is to learn to choose the right in the face of that opposition, thereby gaining essential experience and wisdom. The level of intelligence we attain in this life will rise in the Resurrection (Doctrine and Covenants 130:18–19). Bodies will then be immortal like those of the Father and the Son (Philippians 3:21), but the degree of glory to which each person will resurrect is contingent upon the Final Judgment (Revelation 20:13, 1 Corinthians 15:40–41). Those who are worthy to return to God's presence can continue to progress towards a fullness of God's glory, which Mormons refer to as eternal life, or exaltation (Doctrine and Covenants 76).
The Latter-day Saint concept of apotheosis/exaltation is expressed in Latter-day scriptures (Mosiah 3:19, Alma 13:12, D&C 78:7, D&C 78:22, D&C 84:4, D&C 84:23, D&C 88:68, D&C 93:28) and is expressed by a member of the Quorum of the Twelve Apostles: "Though stretched by our challenges, by living righteously and enduring well we can eventually become sufficiently more like Jesus in our traits and attributes, that one day we can dwell in the Father's presence forever and ever" (Neal Maxwell, October 1997).
In early 2014, the Church of Jesus Christ of Latter-day Saints published an essay on the official church website specifically addressing the foundations, history, and official beliefs regarding apotheosis. The essay addresses the scriptural foundations of this belief, teachings of the early Church Fathers on the subject of deification, and the teachings of modern Church leaders, starting with Joseph Smith.
=== Wesleyan Protestantism ===
Distinctively, in Wesleyan Protestantism theosis sometimes implies the doctrine of entire sanctification which teaches, in summary, that it is the Christian's goal, in principle possible to achieve, to live without any (voluntary) sin (Christian perfection). Wesleyan theologians detect the influence on Wesley from the Eastern Fathers, who saw the drama of salvation leading to the deification (apotheosis) of the human, in order that such perfection as originally part of human nature in creation but distorted by the fall might bring fellowship with the divine.
== Druze faith ==
The Druze faith further split from Isma'ilism as it developed its own unique doctrines, and finally separated from both Ismāʿīlīsm and Islam altogether; these include the belief that the Imam Al-Ḥākim bi-Amr Allāh was God incarnate. Hamza ibn Ali ibn Ahmad is considered the founder of the Druze faith and the primary author of the Druze manuscripts, he proclaimed that God became flesh, assumed a human nature, and became a man in the form of al-Hakim bi-Amr Allah.
Historian David R. W. Bryer defines the Druzes as ghulat of Isma'ilism, since they exaggerated the cult of the caliph al-Hakim bi-Amr Allah and considered him divine; he also defines the Druzes as a religion that deviated from Islam. He also added that as a result of this deviation, the Druze faith "seems as different from Islam as Islam is from Christianity or Christianity is from Judaism". The Druze deify al-Hākim bi-Amr Allāh, attributing to him divine qualities similar to those Christians attribute to Jesus.
== Music ==
Apart from the visual arts, several works of classical music use the term in the titles or works or sections.
In French Baroque music it was an alternative title to tombeau ("tomb" or "tombstone") for "memorial pieces" for chamber forces to commemorate individuals who were friends or patrons. François Couperin wrote two pieces titled as apotheoses, one for Arcangelo Corelli (Le Parnasse, ou L'Apothéose de Corelli), and one for Jean Baptiste Lully (L'Apothéose de Lully), whose movements have titles such as Enlévement de Lully au Parnasse ("The raising of Lully to Parnassus").
In Romantic music, apotheosis sections usually contain the appearance of a theme in grand or exalted form, typically as a finale. The term is especially associated with the symphonic works of Franz Liszt, where "the main theme, which may by and large be considered as characterizing the hero, is presented in its constituent elements blown up beyond all proportions and, because it is typically slowed down tremendously, is split up into smaller segments". Such a treatment has often been seen by 20th-century critics as "vacuous bombast".
Richard Wagner famously used the term metaphorically in describing Beethoven's Seventh Symphony as "the apotheosis of the dance".
Hector Berlioz used "Apotheose" as the title of the final movement of his Grande symphonie funèbre et triomphale, a work composed in 1846 for the dedication of a monument to France's war dead. Two of Pyotr Ilyich Tchaikovsky's ballets, The Sleeping Beauty and The Nutcracker, contain apotheoses as finales; the same is true of Ludwig Minkus's La Bayadère. Igor Stravinsky composed two ballets, Apollo and Orpheus, which both contain episodes entitled "Apotheose". The concluding tableau of Maurice Ravel's Ma mère l'Oye is also titled "Apotheose." Czech composer Karel Husa, concerned in 1970 about arms proliferation and environmental deterioration, named his musical response Apotheosis for This Earth. Aram Khachaturian entitled a segment of his ballet Spartacus "Sunrise and Apotheosis."
== Poetry ==
Samuel Menashe (1925–2011) wrote a poem entitled Apotheosis, as did Barbara Kingsolver. Emily Dickinson (1830–1886) wrote Love, Poem 18: Apotheosis. The poet Dejan Stojanović's Dancing of Sounds contains the line, "Art is apotheosis." Paul Laurence Dunbar wrote a poem entitled Love's Apotheosis. Samuel Taylor Coleridge wrote a poem entitled "The Apotheosis, or the Snow-Drop" in 1787.
Parodic Apotheoses include the conclusion of Alexander Pope's mock heroic The Rape of the Lock, where the lock of hair that has caused the dispute rises to the heavens:
== Anthropolatry ==
Anthropolatry is the deification and worship of humans. It was practiced in ancient Japan towards their emperors. Followers of Socinianism were later accused of practicing anthropolatry. Anthropologist Ludwig Feuerbach professed a religion to worship all human beings while Auguste Comte venerated only individuals who made positive contributions and excluded those who did not.
== See also ==
== Notes ==
== References ==
James Hall, A History of Ideas and Images in Italian Art, 1983, John Murray, London, ISBN 0719539714
Garnett, Richard; Mackintosh, Robert (1911). "Apotheosis" . In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 2 (11th ed.). Cambridge University Press. pp. 206–207.
Rehding, Alexander, Music and Monumentality: Commemoration and Wonderment in Nineteenth Century Germany, 2009, Oxford University Press, ISBN 9780199736652, google books
"Smith and Wayte": A Dictionary of Greek and Roman Antiquities, by William Smith, LLD, William Wayte, and G. E. Marindin, 1890, John Murray, Online via www.perseus.tufts.edu
== Further reading ==
Boak, Arthur E.R. "The Theoretical Basis of the Deification of Rulers in Antiquity", in: Classical Journal vol. 11, 1916, pp. 293–297.
Bömer, Franz. "Ahnenkult und Ahnenglaube im alten Rom", Leipzig 1943.
Burkert, Walter. "Caesar und Romulus-Quirinus", in: Historia vol. 11, 1962, pp. 356–376.
Engels, David. "Postea dictus est inter deos receptus. Wetterzauber und Königsmord: Zu den Hintergründen der Vergöttlichung frührömischer Könige", in: Gymnasium vol 114, 2007, pp. 103–130.
Kalakaua, David. "The Apotheosis of Pele: The Adventures of the Goddess with Kamapuaa" in The Legends and Myths of Hawaii
King, Stephen. "The Dark Tower: The Gunslinger
Liou-Gille, Bernadette. "Divinisation des morts dans la Rome ancienne", in: Revue Belge de Philologie vol. 71, 1993, pp. 107–115.
Richard, Jean-Claude. "Énée, Romulus, César et les funérailles impériales", in:Mélanges de l'École française de Rome vol. 78, 1966, pp. 67–78.
Subin, Anna Della. Accidental Gods: On Men Unwittingly Turned Divine, Granta (expected January 2022)
Cook, John Granger. Empty Tomb, Resurrection, Apotheosis. Germany, Mohr Siebeck, 2018.
== External links ==
'Living with Gods': BBC Four Thought talk with Anna Della Subin, author of Accidental Gods, 16 January 2020
Seneca's Apocolocyntosis at Project Gutenberg
François Couperin. "L'Apothéose de Corelli" and "L'Apothéose de Lully" at IMSLP | Apotheosis (from Ancient Greek ἀποθέωσις (apothéōsis), from ἀποθεόω/ἀποθεῶ (apotheóō/apotheô) 'to deify'), also called divinization or deification (from Latin deificatio 'making divine'), is the glorification of a subject to divine levels and, commonly, the treatment of a human being, any other living thing, or an abstract idea in the likeness of a deity.
The original sense of apotheosis relates to religion and is the subject of many works of art. Figuratively "apotheosis" may be used in almost any context for "the deification, glorification, or exaltation of a principle, practice, etc.", so normally attached to an abstraction of some sort.
In religion, apotheosis was a feature of many religions in the ancient world, and some that are active today. It requires a belief that there is a possibility of newly-created gods, so a polytheistic belief system. The major modern religions of Christianity, Islam, and Judaism do not allow for this, though many recognise minor sacred categories such as saints (created by a process called canonization). In Christian theology there is a concept of the faithful becoming god-like, called divinization or in Eastern Christianity theosis. In Hinduism there is some scope for new deities. A human may be deified by becoming regarded as an avatar of an established deity, usually a major one, or by being regarded as a new, independent, deity (usually a minor one), or some mixture of the two.
In art, an apotheosis scene typically shows the subject in the heavens or rising towards them, often accompanied by a number of angels, putti, personifications of virtues, or similar figures. Especially from Baroque art onwards, apotheosis scenes may depict rulers, generals or artists purely as an honorific metaphor; in many cases the "religious" context is classical Greco-Roman pagan religion, as in The Apotheosis of Voltaire, featuring Apollo. The Apotheosis of Washington (1865), high up in the dome of the United States Capitol Building, is another example. Personifications of places or abstractions are also showed receiving an apotheosis. The typical composition was suitable for placement on ceilings or inside domes.
| 14 |
313 | apotheosis | Apotheosis (film) (wikipedia) | Apotheosis is a 1970 film directed by John Lennon and Yoko Ono.
== Plot ==
The film depicts a 17-minute-long journey on a balloon as it ascends and finally rises into the clouds. Lennon and Ono appear at the start of the film dressed in dark cloaks and hoods.
== Production ==
The film was shot in the village of Lavenham in Suffolk in eastern England; the couple had decided to reject footage from an earlier filming attempt in the Hampshire town of Basingstoke. Lennon and Ono arrived at Lavenham's Market Place in their white Rolls-Royce driven by a chauffeur and booked into the nearby Bull Hotel in Long Melford as 'Mr and Mrs Smith'. The couple were accompanied by a film crew who were shooting a documentary for the BBC, The World of John and Yoko, which was broadcast over the Christmas period of 1969.
A local building company, W A Deacon & Sons, erected scaffolding to secure the balloon before release. The workers also helped lift Lennon and Ono into and out of the basket. A photograph of Lennon and Ono in the balloon was on the front cover of the East Anglian Daily Times on the following Monday. The couple left the basket shortly before the launch of the balloon, causing members of the public who had gathered to heckle them.
Nic Kowland, a frequent technical collaborator on films made by Ono, helped with the technical aspects of the film. The idea for the film came from discussions the couple had had while making their album cover for Two Virgins while nude.
The 22,000 cubic metres (780,000 cu ft) of gas that filled the balloon cost £350, and permission for the flight was granted by the Ministry of Defence and Lavenham Parish Council. The parish council had been contacted by the Beatles' company Apple Corps two days prior to the shoot to ask permission to shoot the film. In a 2010 interview Ono said that making the film in Lavenham was "truly lovely" and that she would "love to go back there ... but it's not the same for me without John". The couple had previously directed the films Rape and Fly and subsequently collaborated on Up Your Legs Forever.
== Reception ==
In 1972 the critic Jonas Mekas described the point at which the camera rose above the clouds as: "suddenly the cloud landscape opened up like a huge poem, you could see the tops of the clouds, all beautifully enveloped by sun, stretching into infinity..."
The film was shown at the 1971 Cannes Film Festival. It was also shown at the Tate Britain exhibition A Century of Artists' Film in Britain between 19 May 2003 and 18 April 2004.
== References ==
== Further reading ==
Vogel, Amos. "John & Yoko at Cannes: 'I made a glass hammer'". The Village Voice. June 24, 1971.
== External links ==
Apotheosis at IMDb | Apotheosis is a 1970 film directed by John Lennon and Yoko Ono. | 0 |
314 | apotheosis | Douglas Hill (wikipedia) | Douglas Arthur Hill (6 April 1935 – 21 June 2007) was a Canadian science fiction author, editor and reviewer. He was born in Brandon, Manitoba, the son of a railroad engineer, and was raised in Prince Albert, Saskatchewan. An avid science fiction reader from an early age, he studied English at the University of Saskatchewan (where he earned an Honours B.A. in 1957) and at the University of Toronto. He married fellow writer and U. of S. alumna Gail Robinson in 1958; they moved to Britain in 1959, where he worked as a freelance writer and editor for Aldus Books. In 1967–1968 he served as assistant editor of the controversial New Worlds science fiction magazine under Michael Moorcock.
A lifetime leftist, he served from 1971 to 1984 as the Literary Editor of the socialist weekly Tribune (a position once held by George Orwell), where he regularly reviewed science fiction despite the continued refusal of the literary world to take it seriously. Before starting to write fiction in 1978, he wrote many books on history, science and folklore. Using the pseudonym Martin Hillman, he also worked as an editor of several anthologies, among them Window on the Future (1966), The Shape of Sex to Come (1978), Out of Time (1984), and Hidden Turnings (1988). He is probably best known for his The Last Legionary quintet of novels, supposedly produced as the result of a challenge by a publisher to Hill's complaints about the lack of good science fiction for younger readers.
Hill and his wife had one child, a son. They were divorced in 1978. He lived in Wood Green, London, and died in London after being struck by a bus at a zebra crossing. His death occurred one day after he completed his last trilogy, the Demon Stalkers.
== Writing science-fiction/fantasy for children ==
His most well-known series for younger children appears to have been The Last Legionary quintet. Starting with Galactic Warlord the quartet (the fifth book was a prequel anthology) told the story of Keill Randor, last survivor of a murdered world, seeking revenge for the genocide, aided by a secretive group of advisers known as The Overseers and a winged, telepathic alien named Glr. The series contained the tropes of 'well-intentioned' Science perverted by ego and over-confidence into evil, and the 'good' science being used as the servant not master of humanity. The series also had the trope that elderly people are not irrelevant and worthless, but the smartest, wisest people around and the ones who really know what is going on.
Both The Huntsman and Colsec trilogies continued the tropes and themes of youth alienation caused by being disenfranchised, not lumping all aliens [foreigners] together, mismanagement of natural resources by the industrial military complex, and how disparate individuals can work together and find common ground for the greater good. Hill also explored these ideas in writing fantasy as well as science-fiction series, first in Poisoner and then Demon Stalkers.
His books were popular in schools as their straightforward action and sci-fi or sword-and-sorcery themes appealed to impatient or inattentive readers, particularly boys, who were increasingly difficult to engage in 'reading for pleasure and leisure' and above all they were relatively short-length books without a great deal of background waffle. Whilst still at school and having become a volunteer 'pupil librarian', one writer and tutor was tasked with encouraging her teenage male peers to borrow more books from the school library and take up reading as a recreational activity and recommending books that would facilitate this from potential new stock; she found through peer reviews, questionnaires and a mini-poll that, 'alongside the contemporary, competitive sports-based stories of authors such as Michael Hardcastle and the humorous stories of such as Dick King-Smith, the other of the 'big three' for boys was Douglas Hill. They liked the fast pace, the paring away of extraneous words and the compact length of the books, as well as that although each novel was a complete story, it existed within a 'universe' that enabled them to not have to learn a whole set of new characters each time.'
Another advantage to sustain the increased reading interest of boys was that Hill produced his novels fairly quickly—he had five books published between 1980 and 1982, which meant the engaged interest of young readers was kept as there was another title ready when they finished a previous one.
== Writing science-fiction/fantasy for adults ==
In the early 1990s he decided to develop a fantasy trilogy for adult readers; published in 1994 The Lightless Dome has the main protagonist of Jared 'Red' Cordell, who finds himself transported from contemporary 1990s Earth to a planet where sorcery and Mediaeval style knights and kingdoms exist – he finds that he is apparently descended from or possibly the genetic Doppelganger of a legendary warrior, Red Corodel, who mysteriously disappeared centuries before and who is viewed as the only hope of thwarting a power-crazed sorcerer intent on achieving global tyranny through Apotheosis – becoming a god. Again the series examines the concept of an individual's ideals of personal integrity and community responsibility and at what point does altruism become destructive rather than constructive, and also the issues of spin and media manipulation as initially, he enjoys being in his own 'Conan the Barbarian' movie and plays on the perks of being mistaken for Red Corodel returned to save the day.
A sequel "The Leafless Forest" was published in 1994; however, the last part to the trilogy "The Limitless Bridge" was not released and remains unavailable.
== Bibliography ==
=== Series ===
==== Last Legionary ====
Galactic Warlord (1979)
Deathwing Over Veynaa (1980)
Day of the Starwind (1980)
Planet of the Warlord (1981)
Young Legionary (1982)
Young Legionary is chronologically the first in the series.
==== Demon Stalkers ====
Prey (2008)
Torment (2008)
Vengeance (2009)
Prey is chronologically the first in the series.
==== Huntsman ====
The Huntsman (1982), ISBN 0-434-94284-7
Warriors of the Wasteland (1983), ISBN 0-434-94283-9
Alien Citadel (1984), ISBN 0-434-94282-0
==== Colsec ====
Exiles of Colsec (1984), ISBN 0-575-03348-7
The Caves of Klydor (1984), ISBN 0-575-03413-0
Colsec Rebellion (1985), ISBN 0-575-03610-9
==== Poisoner ====
Blade of the Poisoner (1987), ISBN 0-575-03954-X
Master of Fiends (1987), ISBN 0-575-04095-5
==== Del Curb, Cosmic Courier ====
The Fraxilly Fracas (1989), ISBN 0-575-04403-9
The Colloghi Conspiracy (1990), ISBN 0-575-04579-5
==== Apotheosis ====
The Lightless Dome (1993), ISBN 0-330-32770-4
The Leafless Forest (1994), ISBN 0-330-32960-X
The Limitless Bridge (1996), ISBN 0-330-33842-0 [ISBN allocated, never commercially published]
==== Cade ====
Galaxy's Edge (1996), ISBN 0-553-50334-0
The Moons of Lannamur (1996), ISBN 0-553-50330-8
The Phantom Planet (1997), ISBN 0-553-50331-6
=== Other novels ===
The Exploits of Hercules (1978), ISBN 0-330-25448-0
The Illustrated Faerie Queene (1980), ISBN 0-88225-297-6
Have Your Own Extraterrestrial Adventure (1983), ISBN 0-09-930700-6
The Moon Monsters (1984), ISBN 0-434-93024-5
How Jennifer (and Speckle) Saved the Earth (1986), ISBN 0-434-93036-9
Goblin Party (1988), ISBN 0-575-04338-5
Penelope's Pendant (1990), ISBN 0-333-51318-5
The Tale of Trellie the Troog (1991), ISBN 0-563-34781-3
The Unicorn Dream (1992), ISBN 0-434-97674-1
The Voyage of MudJack (1993), ISBN 0-416-18819-2
Penelope's Protest (1994), ISBN 0-330-32727-5
World of the Stiks (1994), ISBN 0-553-40655-8
Penelope's Peril (1994), ISBN 0-330-33302-X
The Magical Tree-castle (1995), ISBN 0-434-96727-0
Malcolm and the Cloud-Stealer (1995), ISBN 0-590-55917-6
Fireball and the Hero (1995), ISBN 0-416-19123-1
The Dragon Charmer (1997), ISBN 0-340-68741-X
Space Girls Don't Cry (1998), ISBN 0-7497-3244-X
Alien Deeps (2000), ISBN 1-902260-55-4
Melleron's Monsters (2000), ISBN 0-19-919270-7
Melleron's Magic (2001), ISBN 0-19-919271-5
Monster Maze (2001), ISBN 1-84299-006-3
Star Dragon (2002), ISBN 1-84299-046-2
=== Plays ===
Window on the Future (1966)
=== Edited anthologies ===
Window on the Future (1966)
Way of the Werewolf (1966)
The Devil His Due (1967)
Warlocks and Warriors (1971)
The Shape of Sex to Come (1978), ISBN 0-330-25091-4
Alien Worlds (1980), ISBN 0-434-94285-5
Planetfall (1986), ISBN 0-19-278113-8
=== Non-fiction ===
The Supernatural (1965)
The Opening of the Canadian West (1967)
Magic and Superstition (1968)
John Keats (1968), ISBN 0-249-43968-9
Regency London (1969), ISBN 0-356-02568-3
A Hundred Years of Georgian London (1970), ISBN 0-356-03264-7
Return from the Dead (1970), ISBN 0-356-03463-1
Fortune Telling (1972), ISBN 0-600-32835-X
The Scots to Canada (1972), ISBN 0-85614-016-3
The English to New England (1975), ISBN 0-85614-021-X
Tribune 40 (1977)
Bridging a Continent (1981, as "Martin Hillman")
Witch and Wizard (1997), ISBN 0-7513-6106-2
=== Anthologies containing stories by Douglas Hill ===
Hidden Turnings (1989), ISBN 0-416-11272-2, ed. Diana Wynne Jones
Space Stories (1996), ISBN 1-85487-451-9, ed. Mike Ashley
=== Short stories ===
"Hally's Paradise" (1984)
"True Believer" (1989)
=== Plays ===
Roulette
== See also ==
The Last Legionary series
== Notes ==
== External links ==
Obituary in The Independent
Obituary in The Guardian
1995 profile of Hill Archived 5 September 2004 at the Wayback Machine
Douglas Hill at Library of Congress, with 38 library catalogue records
Douglas Hill at the Internet Speculative Fiction Database | Douglas Arthur Hill (6 April 1935 – 21 June 2007) was a Canadian science fiction author, editor and reviewer. He was born in Brandon, Manitoba, the son of a railroad engineer, and was raised in Prince Albert, Saskatchewan. An avid science fiction reader from an early age, he studied English at the University of Saskatchewan (where he earned an Honours B.A. in 1957) and at the University of Toronto. He married fellow writer and U. of S. alumna Gail Robinson in 1958; they moved to Britain in 1959, where he worked as a freelance writer and editor for Aldus Books. In 1967–1968 he served as assistant editor of the controversial New Worlds science fiction magazine under Michael Moorcock.
A lifetime leftist, he served from 1971 to 1984 as the Literary Editor of the socialist weekly Tribune (a position once held by George Orwell), where he regularly reviewed science fiction despite the continued refusal of the literary world to take it seriously. Before starting to write fiction in 1978, he wrote many books on history, science and folklore. Using the pseudonym Martin Hillman, he also worked as an editor of several anthologies, among them Window on the Future (1966), The Shape of Sex to Come (1978), Out of Time (1984), and Hidden Turnings (1988). He is probably best known for his The Last Legionary quintet of novels, supposedly produced as the result of a challenge by a publisher to Hill's complaints about the lack of good science fiction for younger readers.
Hill and his wife had one child, a son. They were divorced in 1978. He lived in Wood Green, London, and died in London after being struck by a bus at a zebra crossing. His death occurred one day after he completed his last trilogy, the Demon Stalkers. | 12 |
315 | immunology | Immunologie (wiktionary) | IPA(key): /ɪmunoloˈɡiː/
Immunologie f (genitive Immunologie, no plural)
immunology
immunologisch
“Immunologie” in Digitales Wörterbuch der deutschen Sprache
“Immunologie” in Uni Leipzig: Wortschatz-Lexikon
“Immunologie” in Duden online | IPA(key): /ɪmunoloˈɡiː/
Immunologie f (genitive Immunologie, no plural)
immunology
immunologisch
“Immunologie” in Digitales Wörterbuch der deutschen Sprache
“Immunologie” in Uni Leipzig: Wortschatz-Lexikon
“Immunologie” in Duden online | 6 |
316 | immunology | immunologie (wiktionary) | From immuno- + -logie.
IPA(key): /i.my.nɔ.lɔ.ʒi/
immunologie f (plural immunologies)
immunology
immunologique
immunologiste
→ Persian: ایمونولوژی (imunoloži)
→ Romanian: imunologie
→ Turkish: immünoloji
“immunologie”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.
immunologie f
plural of immunologia | From immuno- + -logie.
IPA(key): /i.my.nɔ.lɔ.ʒi/
immunologie f (plural immunologies)
immunology
immunologique
immunologiste
→ Persian: ایمونولوژی (imunoloži)
→ Romanian: imunologie
→ Turkish: immünoloji
“immunologie”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.
immunologie f
plural of immunologia | 7 |
317 | immunology | immunology (wiktionary) | immune + -ology
immunology (usually uncountable, plural immunologies)
(medicine) The branch of medicine that concerns the body's immune system. | immune + -ology
immunology (usually uncountable, plural immunologies)
(medicine) The branch of medicine that concerns the body's immune system. | 3 |
318 | immunology | Immunology (wikipedia) | Immunology is a branch of biology and medicine that covers the study of immune systems in all organisms.
Immunology charts, measures, and contextualizes the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders (such as autoimmune diseases, hypersensitivities, immune deficiency, and transplant rejection); and the physical, chemical, and physiological characteristics of the components of the immune system in vitro, in situ, and in vivo. Immunology has applications in numerous disciplines of medicine, particularly in the fields of organ transplantation, oncology, rheumatology, virology, bacteriology, parasitology, psychiatry, and dermatology.
The term was coined by Russian biologist Ilya Ilyich Mechnikov, who advanced studies on immunology and received the Nobel Prize for his work in 1908 with Paul Ehrlich "in recognition of their work on immunity". He pinned small thorns into starfish larvae and noticed unusual cells surrounding the thorns. This was the active response of the body trying to maintain its integrity. It was Mechnikov who first observed the phenomenon of phagocytosis, in which the body defends itself against a foreign body. Ehrlich accustomed mice to the poisons ricin and abrin. After feeding them with small but increasing dosages of ricin he ascertained that they had become "ricin-proof". Ehrlich interpreted this as immunization and observed that it was abruptly initiated after a few days and was still in existence after several months.
Prior to the designation of immunity, from the etymological root immunis, which is Latin for 'exempt', early physicians characterized organs that would later be proven as essential components of the immune system. The important lymphoid organs of the immune system are the thymus, bone marrow, and chief lymphatic tissues such as spleen, tonsils, lymph vessels, lymph nodes, adenoids, and liver. However, many components of the immune system are cellular in nature, and not associated with specific organs, but rather embedded or circulating in various tissues located throughout the body.
== Classical immunology ==
Classical immunology ties in with the fields of epidemiology and medicine. It studies the relationship between the body systems, pathogens, and immunity. The earliest written mention of immunity can be traced back to the plague of Athens in 430 BCE. Thucydides noted that people who had recovered from a previous bout of the disease could nurse the sick without contracting the illness a second time. Many other ancient societies have references to this phenomenon, but it was not until the 19th and 20th centuries before the concept developed into scientific theory.
The study of the molecular and cellular components that comprise the immune system, including their function and interaction, is the central science of immunology. The immune system has been divided into a more primitive innate immune system and, in vertebrates, an acquired or adaptive immune system. The latter is further divided into humoral (or antibody) and cell-mediated components.
The immune system has the capability of self and non-self-recognition. An antigen is a substance that ignites the immune response. The cells involved in recognizing the antigen are Lymphocytes. Once they recognize, they secrete antibodies. Antibodies are proteins that neutralize the disease-causing microorganisms. Antibodies do not directly kill pathogens, but instead, identify antigens as targets for destruction by other immune cells such as phagocytes or NK cells.
The (antibody) response is defined as the interaction between antibodies and antigens. Antibodies are specific proteins released from a certain class of immune cells known as B lymphocytes, while antigens are defined as anything that elicits the generation of antibodies (antibody generators). Immunology rests on an understanding of the properties of these two biological entities and the cellular response to both.
It is now getting clear that the immune responses contribute to the development of many common disorders not traditionally viewed as immunologic, including metabolic, cardiovascular, cancer, and neurodegenerative conditions like Alzheimer's disease. Besides, there are direct implications of the immune system in the infectious diseases (tuberculosis, malaria, hepatitis, pneumonia, dysentery, and helminth infestations) as well. Hence, research in the field of immunology is of prime importance for the advancements in the fields of modern medicine, biomedical research, and biotechnology.
Immunological research continues to become more specialized, pursuing non-classical models of immunity and functions of cells, organs and systems not previously associated with the immune system (Yemeserach 2010).
== Diagnostic immunology ==
The specificity of the bond between antibody and antigen has made the antibody an excellent tool for the detection of substances by a variety of diagnostic techniques. Antibodies specific for a desired antigen can be conjugated with an isotopic (radio) or fluorescent label or with a color-forming enzyme in order to detect it. However, the similarity between some antigens can lead to false positives and other errors in such tests by antibodies cross-reacting with antigens that are not exact matches.
== Immunotherapy ==
The use of immune system components or antigens to treat a disease or disorder is known as immunotherapy. Immunotherapy is most commonly used to treat allergies, autoimmune disorders such as Crohn's disease, Hashimoto's thyroiditis and rheumatoid arthritis, and certain cancers. Immunotherapy is also often used for patients who are immunosuppressed (such as those with HIV) and people with other immune deficiencies.
This includes regulating factors such as IL-2, IL-10, GM-CSF B, IFN-α.
== Clinical immunology ==
Clinical immunology is the study of diseases caused by disorders of the immune system (failure, aberrant action, and malignant growth of the cellular elements of the system). It also involves diseases of other systems, where immune reactions play a part in the pathology and clinical features.
The diseases caused by disorders of the immune system fall into two broad categories:
immunodeficiency, in which parts of the immune system fail to provide an adequate response (examples include chronic granulomatous disease and primary immune diseases);
autoimmunity, in which the immune system attacks its own host's body (examples include systemic lupus erythematosus, rheumatoid arthritis, Hashimoto's disease and myasthenia gravis).
Other immune system disorders include various hypersensitivities (such as in asthma and other allergies) that respond inappropriately to otherwise harmless compounds.
The most well-known disease that affects the immune system itself is AIDS, an immunodeficiency characterized by the suppression of CD4+ ("helper") T cells, dendritic cells and macrophages by the human immunodeficiency virus (HIV).
Clinical immunologists also study ways to prevent the immune system's attempts to destroy allografts (transplant rejection).
Clinical immunology and allergy is usually a subspecialty of internal medicine or pediatrics. Fellows in Clinical Immunology are typically exposed to many of the different aspects of the specialty and treat allergic conditions, primary immunodeficiencies and systemic autoimmune and autoinflammatory conditions. As part of their training fellows may do additional rotations in rheumatology, pulmonology, otorhinolaryngology, dermatology and the immunologic lab.
=== Clinical and pathology immunology ===
When health conditions worsen to emergency status, portions of immune system organs, including the thymus, spleen, bone marrow, lymph nodes, and other lymphatic tissues, can be surgically excised for examination while patients are still alive.
== Theoretical immunology ==
Immunology is strongly experimental in everyday practice but is also characterized by an ongoing theoretical attitude. Many theories have been suggested in immunology from the end of the nineteenth century up to the present time. The end of the 19th century and the beginning of the 20th century saw a battle between "cellular" and "humoral" theories of immunity. According to the cellular theory of immunity, represented in particular by Elie Metchnikoff, it was cells – more precisely, phagocytes – that were responsible for immune responses. In contrast, the humoral theory of immunity, held by Robert Koch and Emil von Behring, among others, stated that the active immune agents were soluble components (molecules) found in the organism's "humors" rather than its cells.
In the mid-1950s, Macfarlane Burnet, inspired by a suggestion made by Niels Jerne, formulated the clonal selection theory (CST) of immunity. On the basis of CST, Burnet developed a theory of how an immune response is triggered according to the self/nonself distinction: "self" constituents (constituents of the body) do not trigger destructive immune responses, while "nonself" entities (e.g., pathogens, an allograft) trigger a destructive immune response. The theory was later modified to reflect new discoveries regarding histocompatibility or the complex "two-signal" activation of T cells. The self/nonself theory of immunity and the self/nonself vocabulary have been criticized, but remain very influential.
More recently, several theoretical frameworks have been suggested in immunology, including "autopoietic" views, "cognitive immune" views, the "danger model" (or "danger theory"), and the "discontinuity" theory. The danger model, suggested by Polly Matzinger and colleagues, has been very influential, arousing many comments and discussions.
== Developmental immunology ==
The body's capability to react to antigens depends on a person's age, antigen type, maternal factors and the area where the antigen is presented. Neonates are said to be in a state of physiological immunodeficiency, because both their innate and adaptive immunological responses are greatly suppressed. Once born, a child's immune system responds favorably to protein antigens while not as well to glycoproteins and polysaccharides. In fact, many of the infections acquired by neonates are caused by low virulence organisms like Staphylococcus and Pseudomonas. In neonates, opsonic activity and the ability to activate the complement cascade is very limited. For example, the mean level of C3 in a newborn is approximately 65% of that found in the adult. Phagocytic activity is also greatly impaired in newborns. This is due to lower opsonic activity, as well as diminished up-regulation of integrin and selectin receptors, which limit the ability of neutrophils to interact with adhesion molecules in the endothelium. Their monocytes are slow and have a reduced ATP production, which also limits the newborn's phagocytic activity. Although, the number of total lymphocytes is significantly higher than in adults, the cellular and humoral immunity is also impaired. Antigen-presenting cells in newborns have a reduced capability to activate T cells. Also, T cells of a newborn proliferate poorly and produce very small amounts of cytokines like IL-2, IL-4, IL-5, IL-12, and IFN-g which limits their capacity to activate the humoral response as well as the phagocitic activity of macrophage. B cells develop early during gestation but are not fully active.
Maternal factors also play a role in the body's immune response. At birth, most of the immunoglobulin present is maternal IgG. These antibodies are transferred from the placenta to the fetus using the FcRn (neonatal Fc receptor). Because IgM, IgD, IgE and IgA do not cross the placenta, they are almost undetectable at birth. Some IgA is provided by breast milk. These passively-acquired antibodies can protect the newborn for up to 18 months, but their response is usually short-lived and of low affinity. These antibodies can also produce a negative response. If a child is exposed to the antibody for a particular antigen before being exposed to the antigen itself then the child will produce a dampened response. Passively acquired maternal antibodies can suppress the antibody response to active immunization. Similarly, the response of T-cells to vaccination differs in children compared to adults, and vaccines that induce Th1 responses in adults do not readily elicit these same responses in neonates. Between six and nine months after birth, a child's immune system begins to respond more strongly to glycoproteins, but there is usually no marked improvement in their response to polysaccharides until they are at least one year old. This can be the reason for distinct time frames found in vaccination schedules.
During adolescence, the human body undergoes various physical, physiological and immunological changes triggered and mediated by hormones, of which the most significant in females is 17-β-estradiol (an estrogen) and, in males, is testosterone. Estradiol usually begins to act around the age of 10 and testosterone some months later. There is evidence that these steroids not only act directly on the primary and secondary sexual characteristics but also have an effect on the development and regulation of the immune system, including an increased risk in developing pubescent and post-pubescent autoimmunity. There is also some evidence that cell surface receptors on B cells and macrophages may detect sex hormones in the system.
The female sex hormone 17-β-estradiol has been shown to regulate the level of immunological response, while some male androgens such as testosterone seem to suppress the stress response to infection. Other androgens, however, such as DHEA, increase immune response. As in females, the male sex hormones seem to have more control of the immune system during puberty and post-puberty than during the rest of a male's adult life.
Physical changes during puberty such as thymic involution also affect immunological response.
== Ecoimmunology and behavioural immunity ==
Ecoimmunology, or ecological immunology, explores the relationship between the immune system of an organism and its social, biotic and abiotic environment.
More recent ecoimmunological research has focused on host pathogen defences traditionally considered "non-immunological", such as pathogen avoidance, self-medication, symbiont-mediated defenses, and fecundity trade-offs. Behavioural immunity, a phrase coined by Mark Schaller, specifically refers to psychological pathogen avoidance drivers, such as disgust aroused by stimuli encountered around pathogen-infected individuals, such as the smell of vomit. More broadly, "behavioural" ecological immunity has been demonstrated in multiple species. For example, the Monarch butterfly often lays its eggs on certain toxic milkweed species when infected with parasites. These toxins reduce parasite growth in the offspring of the infected Monarch. However, when uninfected Monarch butterflies are forced to feed only on these toxic plants, they suffer a fitness cost as reduced lifespan relative to other uninfected Monarch butterflies. This indicates that laying eggs on toxic plants is a costly behaviour in Monarchs which has probably evolved to reduce the severity of parasite infection.
Symbiont-mediated defenses are also heritable across host generations, despite a non-genetic direct basis for the transmission. Aphids, for example, rely on several different symbionts for defense from key parasites, and can vertically transmit their symbionts from parent to offspring. Therefore, a symbiont that successfully confers protection from a parasite is more likely to be passed to the host offspring, allowing coevolution with parasites attacking the host in a way similar to traditional immunity.
The preserved immune tissues of extinct species, such as the thylacine (Thylacine cynocephalus), can also provide insights into their biology.
== Cancer immunology ==
The study of the interaction of the immune system with cancer cells can lead to diagnostic tests and therapies with which to find and fight cancer. The immunology concerned with physiological reaction characteristic of the immune state.
== Reproductive immunology ==
This area of the immunology is devoted to the study of immunological aspects of the reproductive process including fetus acceptance. The term has also been used by fertility clinics to address fertility problems, recurrent miscarriages, premature deliveries and dangerous complications such as pre-eclampsia.
== See also ==
List of immunologists
Immunomics
International Reviews of Immunology
Outline of immunology
History of immunology
Osteoimmunology
== References ==
== External links ==
Media related to Immunology at Wikimedia Commons
American Association of Immunologists
British Society for Immunology
Federation of Clinical Immunology Societies | Immunology is a branch of biology and medicine that covers the study of immune systems in all organisms.
Immunology charts, measures, and contextualizes the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders (such as autoimmune diseases, hypersensitivities, immune deficiency, and transplant rejection); and the physical, chemical, and physiological characteristics of the components of the immune system in vitro, in situ, and in vivo. Immunology has applications in numerous disciplines of medicine, particularly in the fields of organ transplantation, oncology, rheumatology, virology, bacteriology, parasitology, psychiatry, and dermatology.
The term was coined by Russian biologist Ilya Ilyich Mechnikov, who advanced studies on immunology and received the Nobel Prize for his work in 1908 with Paul Ehrlich "in recognition of their work on immunity". He pinned small thorns into starfish larvae and noticed unusual cells surrounding the thorns. This was the active response of the body trying to maintain its integrity. It was Mechnikov who first observed the phenomenon of phagocytosis, in which the body defends itself against a foreign body. Ehrlich accustomed mice to the poisons ricin and abrin. After feeding them with small but increasing dosages of ricin he ascertained that they had become "ricin-proof". Ehrlich interpreted this as immunization and observed that it was abruptly initiated after a few days and was still in existence after several months.
Prior to the designation of immunity, from the etymological root immunis, which is Latin for 'exempt', early physicians characterized organs that would later be proven as essential components of the immune system. The important lymphoid organs of the immune system are the thymus, bone marrow, and chief lymphatic tissues such as spleen, tonsils, lymph vessels, lymph nodes, adenoids, and liver. However, many components of the immune system are cellular in nature, and not associated with specific organs, but rather embedded or circulating in various tissues located throughout the body.
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319 | immunology | Immunology (journal) (wikipedia) | Immunology is a monthly peer-reviewed medical journal covering all aspects of immunology. The editor-in-chief is Greg Delgoffe (University of Pittsburgh). It was established in 1958 and is published by Wiley-Blackwell. Through 2021, Immunology was an official journal of the British Society for Immunology.
== Abstracting and indexing ==
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2020 impact factor of 7.397.
== References ==
== External links ==
Official website | Immunology is a monthly peer-reviewed medical journal covering all aspects of immunology. The editor-in-chief is Greg Delgoffe (University of Pittsburgh). It was established in 1958 and is published by Wiley-Blackwell. Through 2021, Immunology was an official journal of the British Society for Immunology.
| 3 |
320 | energy supply | Energieversorgung (wiktionary) | Energie + Versorgung
Energieversorgung f (genitive Energieversorgung, plural Energieversorgungen)
energy supply
power supply
“Energieversorgung” in Digitales Wörterbuch der deutschen Sprache
“Energieversorgung” in Uni Leipzig: Wortschatz-Lexikon
“Energieversorgung” in Duden online | Energie + Versorgung
Energieversorgung f (genitive Energieversorgung, plural Energieversorgungen)
energy supply
power supply
“Energieversorgung” in Digitales Wörterbuch der deutschen Sprache
“Energieversorgung” in Uni Leipzig: Wortschatz-Lexikon
“Energieversorgung” in Duden online | 5 |
321 | energy supply | Energy supply (wikipedia) | Energy supply is the delivery of fuels or transformed fuels to point of consumption. It potentially encompasses the extraction, transmission, generation, distribution and storage of fuels. It is also sometimes called energy flow.
This supply of energy can be disrupted by several factors, including imposition of higher energy prices due to action by OPEC or other cartel, war, political disputes, economic disputes, or physical damage to the energy infrastructure due to terrorism. The security of the energy supply is a major concern of national security and energy law.
== Other uses ==
New York Consolidated Laws includes a statutory code called "Energy Law". Article 21 of this code is called "Energy Supply and Production", but rather than a comprehensive code, only consists of one section dealing with renewable energy.
== See also ==
=== General energy topics ===
Energy
Energy form
Energy conservation
Energy density
Energy economics
Energy law
Energy markets and energy derivatives
Energy policy
Energy price
Energy security
Energy quality
Entropy (energy dispersal) and Introduction to entropy
List of energy topics
Market transformation
World energy consumption
Worldwide energy supply
=== Renewable and alternative energy sources ===
Clean Tech Nation
Effects of 2000s energy crisis
Efficient energy use
Geothermal power
Global warming
Intermittent power source
Ocean energy
Renewable energy
Renewable energy commercialization
Renewable heat
Vehicle-to-grid
Wind power
=== By country ===
Japan
United Kingdom
United States
== References ==
== Other sources ==
Lisa Yount, Energy supply: Library in a book (Infobase Publishing, 2005) ISBN 978-0-8160-5577-7 Found at Google Books.
Jon Strand, Energy efficiency and renewable energy supply for the G-7 countries, with emphasis on Germany, Issues 2007–2299, Volumes 7-299 of IMF working paper(International Monetary Fund, 2007) Found at Google Books.
Herberg, Mikkal (2014). Energy Security and the Asia-Pacific: Course Reader. United States: The National Bureau of Asian Research.
Ewan McLeish, Challenges to Our Energy Supply: Can the Earth Survive? (The Rosen Publishing Group, 2009) ISBN 978-1-4358-5357-7 Found at Google Books. | Energy supply is the delivery of fuels or transformed fuels to point of consumption. It potentially encompasses the extraction, transmission, generation, distribution and storage of fuels. It is also sometimes called energy flow.
This supply of energy can be disrupted by several factors, including imposition of higher energy prices due to action by OPEC or other cartel, war, political disputes, economic disputes, or physical damage to the energy infrastructure due to terrorism. The security of the energy supply is a major concern of national security and energy law. | 4 |
322 | youtube channel | Vlog (wikipedia) | A vlog (), also known as a video blog or video log, is a form of blog for which the medium is video. Vlog entries often combine embedded video (or a video link) with supporting text, images, and other metadata. Entries can be recorded in one take or cut into multiple parts. Unlike a more general video diary, vlogs are often recorded depicting the maker throughout.
In recent years, "vlogging" has spawned a large community on social media, becoming one of the most popular forms of digital entertainment. It is popularly believed that, alongside being entertaining, vlogs can deliver deep context through imagery as opposed to written blogs.
Video logs (vlogs) also often take advantage of web syndication to allow for distribution of the video over the Internet, using either the RSS or Atom syndication formats, for automatic aggregation and playback on mobile devices and personal computers (see video podcast). The vlog category is popular on the video-sharing platform YouTube.
== History ==
In the 1980s, New York artist Nelson Sullivan documented his experiences travelling around New York City and South Carolina by recording videos in a distinctive vlog-like style.
On January 2, 2000, Adam Kontras posted a video alongside a blog entry aimed at informing his friends and family of his cross-country move to Los Angeles in pursuit of show business, marking the first post on what would later become the longest-running video blog in history. In November of that year, Adrian Miles posted a video of changing text on a still image, coining the term vog to refer to his video blog. Filmmaker and musician Luuk Bouwman started in 2002 the now-defunct Tropisms.org site as a video diary of his post-college travels, one of the first sites to be called a vlog or videolog. In 2004, Steve Garfield launched his own video blog and declared that year "the year of the video blog".
=== YouTube ===
Vlogging saw a strong increase in popularity beginning in 2005. The most popular video sharing site, YouTube, was founded in February 2005. The site's co-founder Jawed Karim uploaded the first YouTube vlog clip Me at the zoo on his channel "jawed" in April 2005. The ordinary "everydayness" and "dry aesthetics" of Me at the zoo set the tone for the type of amateur vlogging content that would become typical of YouTube, especially among YouTubers. By July 2006, YouTube had become the fifth most popular web destination, with 100 million videos viewed daily and 65,000 new uploads per day. The Yahoo! Videoblogging Group also saw its membership increase dramatically by August 2005.
Many open source content management systems have enabled the inclusion of video content, allowing bloggers to host and administer their own video blogging sites. In addition, the convergence of mobile phones with digital cameras allows publishing of video content to the Web almost as it is recorded. Radio and television stations may use video blogging as a way to help interact more with listeners and viewers.
Throughout the lifetime of the YouTube platform, vloggers have developed large social communities by expressing emotions of vulnerability and encouraging their viewers to do the same. The effect of this emotional exchange between strangers has been documented, for example, in the popularity of bereavement vlogs, in which grieving individuals reassure each other through friendly comments.
=== Miscellaneous events ===
2005, January – Vloggercon, the first vlogger conference, is held in New York City.
2006, November – Irina Slutsky created and hosted The Vloggies, the first annual video blog awards.
2007, May and August – The Wall Street Journal places a grandmother on the front page of its Personal Journal section. In August 2007, she was featured on an ABC World News Tonight segment showing the elderly now becoming involved in the online video world.
=== Guinness World Record ===
In May 2019, Charles Trippy was awarded the Guinness World Record for the "Most Consecutive Daily Personal Video Blogs Posted On YouTube", having recorded 3653 consecutive videos to his Charles and Allie YouTube channel over the previous ten years.
== Uses ==
=== Impressions ===
Vlogs have made it possible to learn about a Vlogger's persona, culture, and impressions using non-verbal hints. Researchers have conducted experiments using crowdsourcing for Amazons Mechanical Turk to determine what kind of personality traits the Vlogger might have. Many Vlogs have been personified by five big personality traits such as Extraversion, Conscientiousness, Agreeableness, Neuroticism, and Openness to Experience. Along with Mechanical Turk, researchers also looked at the cues that take place within Vlogs. Vlogs can be broken down to their elements considering that there are a lot of factors that play in the creation of one such as placement of camera, lighting, location, amount of time spent looking at the camera, pitch, delivery and amount of the interactions. Using this information and crowdsourcing, results have revealed that the highest rate in personality research was Agreeableness which makes Vlogging a great place to form Agreeable impressions. However, more non-verbal hints are more noticeable in other form traits such as Extraversion. Regardless, Personality impressions have made a more interesting Vlog viewing experience.
=== Education ===
Vlogging has been experimented with school systems to determine if it is a reliable platform to deliver higher educational practices to students. Researchers have done an experiment that placed 42 college freshmen into a control and experimental group of 21 each. Oral proficiency exams were given to all students to reflect their current speech skills, after a year of teachings based on each of the groups preference. The control group was instructed to work with their standard writing skills and create their own blogs, while the Experimental group tested their skills with online interaction. Scores for both groups had increased after both tests, however the experimental group had outperformed the control group due to the improvement of speech proficiency that came as a result of a more interactive learning environment between teachers and classmates. The control group claimed that not using video blogs "lowered their confidence" in their speaking proficiency.
=== Health ===
Researchers have investigated how vlog-style YouTube videos made by creators who suffer from chronic illnesses can raise health awareness among viewers and create social communities among those suffering. A 2014 study evaluated the contextual relationship between vloggers who shared that they had diabetes, cancer, or human immunodeficiency virus (HIV) and their audiences. Most of the creators of these vlogs chose to focus their videos on how disease diagnosis and treatment had impacted them physically and emotionally. Commenters on the vlogs who shared personal characteristics formed ad hoc small groups; these impromptu support groups expanded over time as more and more people discovered the health vlogs.
== Live broadcasting ==
YouTube announced a live broadcasting feature called YouTube Live in 2008. This feature was also established by other social platforms such as Instagram, Facebook and Twitch.
== YouTube presence ==
YouTube currently ranks among the top three most-visited sites on the web. As a high traffic area for video bloggers, or vloggers, YouTube has created a platform for these participants to present their personal videos, which oftentimes are filmed using hand held point and shoot cameras. The popularity of vlogs in the YouTube community has risen exponentially in the past few years; out of the top 100 most subscribed YouTube channels, 17 provide vlogs as their primary style of footage. Many of these vloggers are a part of the YouTube Partner Program, which professionalizes the industry and allows for monetary gain from video production. This professionalization additionally helps increase exposure to various channels as well as creates a sense of stability within the field. Additionally, this professionalization allows content creators to be deemed a credible source by their viewers. Furthermore, many vloggers have been able to turn their channels into sustainable careers; in 2013, the highest paid vlogger brought in a minimum of $720,000 for the year. Hollywood is taking notice of this rising medium, and has placed its value ranked over other entertainment companies such as Marvel, which is also owned by Disney.
== See also ==
History of blogging
Lifecasting (video stream)
Livestream
Photoblog
Parasocial interaction
Video podcast
vBook
== References ==
== External links ==
A Certain Tendency in Videoblogging and Rethinking the Rebirth of the Author, academic essay on videoblogging
A Post-Cinema of Distractions: On the Genealogical Constitution of Personal Videoblogging, academic essay on videoblogging
ASL Vlog & Video Directory | A vlog (), also known as a video blog or video log, is a form of blog for which the medium is video. Vlog entries often combine embedded video (or a video link) with supporting text, images, and other metadata. Entries can be recorded in one take or cut into multiple parts. Unlike a more general video diary, vlogs are often recorded depicting the maker throughout.
In recent years, "vlogging" has spawned a large community on social media, becoming one of the most popular forms of digital entertainment. It is popularly believed that, alongside being entertaining, vlogs can deliver deep context through imagery as opposed to written blogs.
Video logs (vlogs) also often take advantage of web syndication to allow for distribution of the video over the Internet, using either the RSS or Atom syndication formats, for automatic aggregation and playback on mobile devices and personal computers (see video podcast). The vlog category is popular on the video-sharing platform YouTube. | 7 |
323 | youtube channel | YouTube (wikipedia) | YouTube is an American online video sharing platform owned by Google. Accessible worldwide, YouTube was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim, three former employees of PayPal. Headquartered in San Bruno, California, United States, it is the second most visited website in the world, after Google Search. YouTube has more than 2.5 billion monthly users, who collectively watch more than one billion hours of videos every day. As of May 2019, videos were being uploaded to the platform at a rate of more than 500 hours of content per minute, and as of 2021, there were approximately 14 billion videos in total.
In October 2006, YouTube was purchased by Google for $1.65 billion (equivalent to $2.31 billion in 2023). Google expanded YouTube's business model of generating revenue from advertisements alone, to offering paid content such as movies and exclusive content produced by and for YouTube. It also offers YouTube Premium, a paid subscription option for watching content without ads. YouTube incorporated Google's AdSense program, generating more revenue for both YouTube and approved content creators. In 2022, YouTube's annual advertising revenue increased to $29.2 billion, more than $9 billion higher than in 2020.
Since its purchase by Google, YouTube has expanded beyond the core website into mobile apps, network television, and the ability to link with other platforms. Video categories on YouTube include music videos, video clips, news, short and feature films, songs, documentaries, movie trailers, teasers and TV spots, live streams, vlogs, and more. Most content is generated by individuals, including collaborations between "YouTubers" and corporate sponsors. Established media, news, and entertainment corporations have also created and expanded their visibility to YouTube channels in order to reach greater audiences.
YouTube has had unprecedented social impact, influencing popular culture, internet trends, and creating multimillionaire celebrities. Despite its growth and success, the platform is sometimes criticized for allegedly facilitating the spread of misinformation, the sharing of copyrighted content, routinely violating its users' privacy, enabling censorship, endangering child safety and wellbeing, and for its inconsistent or incorrect implementation of platform guidelines.
== History ==
=== Founding and initial growth (2005–2006) ===
YouTube was founded by Steve Chen, Chad Hurley, and Jawed Karim. The trio were early employees of PayPal, which left them enriched after the company was bought by eBay. Hurley had studied design at the Indiana University of Pennsylvania, and Chen and Karim studied computer science together at the University of Illinois Urbana-Champaign.
According to a story that has often been repeated in the media, Hurley and Chen developed the idea for YouTube during the early months of 2005, after they had experienced difficulty sharing videos that had been shot at a dinner party at Chen's apartment in San Francisco. Karim did not attend the party and denied that it had occurred, but Chen remarked that the idea that YouTube was founded after a dinner party "was probably very strengthened by marketing ideas around creating a story that was very digestible".
Karim said the inspiration for YouTube came from the Super Bowl XXXVIII halftime show controversy, when Janet Jackson's breast was briefly exposed by Justin Timberlake during the halftime show. Karim could not easily find video clips of the incident and the 2004 Indian Ocean Tsunami online, which led to the idea of a video-sharing site. Hurley and Chen said that the original idea for YouTube was a video version of an online dating service and had been influenced by the website Hot or Not. They created posts on Craigslist asking attractive women to upload videos of themselves to YouTube in exchange for a $100 reward. Difficulty in finding enough dating videos led to a change of plans, with the site's founders deciding to accept uploads of any video.
YouTube began as a venture capital–funded technology startup. Between November 2005 and April 2006, the company raised money from various investors, with Sequoia Capital and Artis Capital Management being the largest two. YouTube's early headquarters were situated above a pizzeria and a Japanese restaurant in San Mateo, California. In February 2005, the company activated www.youtube.com. The first video was uploaded on April 23, 2005. Titled "Me at the zoo", it shows co-founder Jawed Karim at the San Diego Zoo and can still be viewed on the site. In May, the company launched a public beta and by November, a Nike ad featuring Ronaldinho became the first video to reach one million total views. The site launched officially on December 15, 2005, by which time the site was receiving 8 million views a day. Clips at the time were limited to 100 megabytes, as little as 30 seconds of footage.
YouTube was not the first video-sharing site on the Internet; Vimeo was launched in November 2004, though that site remained a side project of its developers from CollegeHumor. The week of YouTube's launch, NBC-Universal's Saturday Night Live ran a skit "Lazy Sunday" by The Lonely Island. Besides helping to bolster ratings and long-term viewership for Saturday Night Live, "Lazy Sunday"'s status as an early viral video helped establish YouTube as an important website. Unofficial uploads of the skit to YouTube drew in more than five million collective views by February 2006 before they were removed when NBCUniversal requested it two months later based on copyright concerns. Despite eventually being taken down, these duplicate uploads of the skit helped popularize YouTube's reach and led to the upload of more third-party content. The site grew rapidly; in July 2006, the company announced that more than 65,000 new videos were being uploaded every day and that the site was receiving 100 million video views per day.
The choice of the name www.youtube.com led to problems for a similarly named website, www.utube.com. That site's owner, Universal Tube & Rollform Equipment, filed a lawsuit against YouTube in November 2006, after being regularly overloaded by people looking for YouTube. Universal Tube subsequently changed its website to www.utubeonline.com.
=== "Broadcast Yourself" era (2006–2013) ===
On October 9, 2006, Google announced that they had acquired YouTube for $1.65 billion in Google stock. The deal was finalized on November 13, 2006. Google's acquisition launched newfound interest in video-sharing sites; IAC, which now owned Vimeo, focused on supporting the content creators to distinguish itself from YouTube. It is at this time YouTube issued the slogan "Broadcast Yourself".
The company experienced rapid growth. The Daily Telegraph wrote that in 2007, YouTube consumed as much bandwidth as the entire Internet in 2000. By 2010, the company had reached a market share of around 43% and more than 14 billion views of videos, according to comScore. That year, the company simplified its interface to increase the time users would spend on the site. In 2011, more than three billion videos were being watched each day with 48 hours of new videos uploaded every minute. However, most of these views came from a relatively small number of videos; according to a software engineer at that time, 30% of videos accounted for 99% of views on the site. That year, the company again changed its interface and at the same time, introduced a new logo with a darker shade of red. A subsequent interface change, designed to unify the experience across desktop, TV, and mobile, was rolled out in 2013. By that point, more than 100 hours were being uploaded every minute, increasing to 300 hours by November 2014.
During this time, the company also went through some organizational changes. In October 2006, YouTube moved to a new office in San Bruno, California. Hurley announced that he would be stepping down as chief executive officer of YouTube to take an advisory role and that Salar Kamangar would take over as head of the company in October 2010.
In December 2009, YouTube partnered with Vevo. In April 2010, Lady Gaga's "Bad Romance" became the most viewed video, becoming the first video to reach 200 million views on May 9, 2010.
YouTube faced a major lawsuit by Viacom International in 2011 that nearly resulted in the discontinuation of the website. The lawsuit was filed as a result of alleged copyright infringement of Viacom's material by YouTube. However, the United States Court of Appeals for the Second Circuit ruled that YouTube was not liable, and thus YouTube won the case in 2012.
=== Susan Wojcicki and going mainstream (2014–2018) ===
Susan Wojcicki was appointed CEO of YouTube in February 2014. In January 2016, YouTube expanded its headquarters in San Bruno by purchasing an office park for $215 million. The complex has 51,468 square metres (554,000 square feet) of space and can house up to 2,800 employees. YouTube officially launched the "polymer" redesign of its user interfaces based on Material Design language as its default, as well a redesigned logo that is built around the service's play button emblem in August 2017.
Through this period, YouTube tried several new ways to generate revenue beyond advertisements. In 2013, YouTube launched a pilot program for content providers to offer premium, subscription-based channels. This effort was discontinued in January 2018 and relaunched in June, with US$4.99 channel subscriptions. These channel subscriptions complemented the existing Super Chat ability, launched in 2017, which allows viewers to donate between $1 and $500 to have their comment highlighted. In 2014, YouTube announced a subscription service known as "Music Key", which bundled ad-free streaming of music content on YouTube with the existing Google Play Music service. The service continued to evolve in 2015 when YouTube announced YouTube Red, a new premium service that would offer ad-free access to all content on the platform (succeeding the Music Key service released the previous year), premium original series, and films produced by YouTube personalities, as well as background playback of content on mobile devices. YouTube also released YouTube Music, a third app oriented towards streaming and discovering the music content hosted on the YouTube platform.
The company also attempted to create products appealing to specific viewers. YouTube released a mobile app known as YouTube Kids in 2015, designed to provide an experience optimized for children. It features a simplified user interface, curated selections of channels featuring age-appropriate content, and parental control features. Also in 2015, YouTube launched YouTube Gaming—a video gaming-oriented vertical and app for videos and live streaming, intended to compete with the Amazon.com-owned Twitch.
The company was attacked on April 3, 2018, when a shooting occurred at YouTube's headquarters in San Bruno, California, which wounded four and resulted in the death of the shooter.
=== Recent history (2019–present) ===
By February 2017, one billion hours of YouTube videos were being watched every day, and 400 hours worth of videos were uploaded every minute. Two years later, the uploads had risen to more than 500 hours per minute. During the COVID-19 pandemic, when most of the world was under stay-at-home orders, usage of services like YouTube significantly increased. One data firm estimated that YouTube was accounting for 15% of all internet traffic, twice its pre-pandemic level. In response to EU officials requesting that such services reduce bandwidth as to make sure medical entities had sufficient bandwidth to share information, YouTube and Netflix stated they would reduce streaming quality for at least thirty days as to cut bandwidth use of their services by 25% to comply with the EU's request. YouTube later announced that they would continue with this move worldwide: "We continue to work closely with governments and network operators around the globe to do our part to minimize stress on the system during this unprecedented situation."
Following a 2018 complaint alleging violations of the Children's Online Privacy Protection Act (COPPA), the company was fined $170 million by the FTC for collecting personal information from minors under the age of 13. YouTube was also ordered to create systems to increase children's privacy. Following criticisms of its implementation of those systems, YouTube started treating all videos designated as "made for kids" as liable under COPPA on January 6, 2020. Joining the YouTube Kids app, the company created a supervised mode, designed more for tweens, in 2021. Additionally, to compete with TikTok, YouTube released YouTube Shorts, a short-form video platform.
During this period, YouTube entered disputes with other tech companies. For over a year, in 2018 and 2019, no YouTube app was available for Amazon Fire products. In 2020, Roku removed the YouTube TV app from its streaming store after the two companies were unable to reach an agreement.
After testing earlier in 2021, YouTube removed public display of dislike counts on videos in November 2021, claiming the reason for the removal was, based on its internal research, that users often used the dislike feature as a form of cyberbullying and brigading. While some users praised the move as a way to discourage trolls, others felt that hiding dislikes would make it harder for viewers to recognize clickbait or unhelpful videos and that other features already existed for creators to limit bullying. YouTube co-founder Jawed Karim referred to the update as "a stupid idea", and that the real reason behind the change was "not a good one, and not one that will be publicly disclosed." He felt that users' ability on a social platform to identify harmful content was essential, saying, "The process works, and there's a name for it: the wisdom of the crowds. The process breaks when the platform interferes with it. Then, the platform invariably declines." Shortly after the announcement, software developer Dmitry Selivanov created Return YouTube Dislike, an open-source, third-party browser extension for Chrome and Firefox that allows users to see a video's number of dislikes. In a letter published on January 25, 2022, by then YouTube CEO Susan Wojcicki, acknowledged that removing public dislike counts was a controversial decision, but reiterated that she stands by this decision, claiming that "it reduced dislike attacks."
In 2022, YouTube launched an experiment where the company would show users who watched longer videos on TVs a long chain of short un-skippable adverts, intending to consolidate all ads into the beginning of a video. Following public outrage over the unprecedented amount of un-skippable ads, YouTube "ended" the experiment on September 19 of that year. In October, YouTube announced that they would be rolling out customizable user handles (e.g. @MrBeast6000) in addition to channel names, which would also become channel URLs.
On February 16, 2023, Wojcicki announced that she would step down as CEO, with Neal Mohan named as her successor. Wojcicki will take on an advisory role for Google and parent company Alphabet.
In late October 2023, YouTube began cracking down on the use of ad blockers on the platform. Users of ad blockers may be given a pop-up warning saying "Video player will be blocked after 3 videos". Users of ad blockers are shown a message asking them to allow ads or inviting them to subscribe to the ad-free YouTube Premium subscription plan. YouTube says that the use of ad blockers violates its terms of service.
In April 2024, YouTube announced it would be "strengthening our enforcement on third-party apps that violate YouTube's Terms of Service, specifically ad-blocking apps".
== Senior leadership ==
YouTube has been led by a CEO since its founding in 2005, beginning with Chad Hurley, who led the company until 2010. After Google's acquisition of YouTube, the CEO role was retained. Salar Kamangar took over Hurley's position and held the job until 2014. He was replaced by Susan Wojcicki, who later resigned in 2023. The current CEO is Neal Mohan, who was appointed on February 16, 2023.
== Features ==
=== Video technology ===
YouTube primarily uses the VP9 and H.264/MPEG-4 AVC video codecs, and the Dynamic Adaptive Streaming over HTTP protocol. MPEG-4 Part 2 streams contained within 3GP containers are also provided for low bandwidth connections. By January 2019, YouTube had begun rolling out videos in AV1 format. In 2021 it was reported that the company was considering requiring AV1 in streaming hardware in order to decrease bandwidth and increase quality. Video is usually streamed alongside the Opus and AAC audio codecs.
At launch in 2005, viewing YouTube videos on a personal computer required the Adobe Flash Player plug-in to be installed in the browser. In January 2010, YouTube launched an experimental version of the site that used the built-in multimedia capabilities of Web browsers supporting HTML video. This allowed videos to be viewed without requiring Adobe Flash Player or any other plug-in to be installed. On January 27, 2015, YouTube announced that HTML video would be the default playback method on supported browsers. HTML video streams use Dynamic Adaptive Streaming over HTTP (MPEG-DASH), an HTTP-based adaptive bit-rate streaming solution optimizes the bitrate and quality for the available network.
The platform can serve videos at optionally lower resolution levels starting at 144p for smoother playback in areas and countries with limited Internet speeds, improving compatibility, as well as for the preservation of limited cellular data plans. The resolution can be adjusted automatically based on detected connection speed or set manually.
From 2008 to 2017, users could add "annotations" to their videos, such as pop-up text messages and hyperlinks, which allowed for interactive videos. By 2019, all annotations had been removed from videos, breaking some videos that depended on the feature. YouTube introduced standardized widgets intended to replace annotations in a cross-platform manner, including "end screens" (a customizable array of thumbnails for specified videos displayed near the end of the video).
In 2018, YouTube became an International Standard Name Identifier (ISNI) registry, and announced its intention to begin creating ISNI identifiers to uniquely identify the musicians whose videos it features.
Users can verify their account, normally through a mobile phone, to gain the ability to upload videos up to 12 hours in length, as well as produce live streams. Users who have built sufficient channel history and have a good track record of complying with the site's Community Guidelines will also gain access to these aforementioned features as well. When YouTube was launched in 2005, it was possible to upload longer videos, but a 10-minute limit was introduced in March 2006 after YouTube found that the majority of videos exceeding this length were unauthorized uploads of television shows and films. The 10-minute limit was increased to 15 minutes in July 2010. Videos can be at most 256 GB in size or 12 hours, whichever is less. As of 2021, automatic closed captions using speech recognition technology when a video is uploaded are available in 13 languages, and can be machine-translated during playback.
YouTube also offers manual closed captioning as part of its creator studio. YouTube formerly offered a 'Community Captions' feature, where viewers could write and submit captions for public display upon approval by the video uploader, but this was deprecated in September 2020.
YouTube accepts the most common container formats, including MP4, Matroska, FLV, AVI, WebM, 3GP, MPEG-PS, and the QuickTime File Format. Some intermediate video formats (i.e., primarily used for professional video editing, not for final delivery or storage) are also accepted, such as ProRes. YouTube provides recommended encoding settings.
Each video is identified by an eleven-character case-sensitive alphanumerical Base64 string in the Uniform Resource Locator (URL) which can contain letters, digits, an underscore (_), and a dash (-).
In 2018, YouTube added a feature called Premiere which displays a notification to the user mentioning when the video will be available for the first time, like for a live stream but with a prerecorded video. When the scheduled time arrives, the video is aired as a live broadcast with a two-minute countdown. Optionally, a premiere can be initiated immediately.
==== Quality and formats ====
YouTube originally offered videos at only one quality level, displayed at a resolution of 320×240 pixels using the Sorenson Spark codec (a variant of H.263), with mono MP3 audio. In June 2007, YouTube added an option to watch videos in 3GP format on mobile phones. In March 2008, a high-quality mode was added, which increased the resolution to 480×360 pixels. In December 2008, 720p HD support was added. At the time of the 720p launch, the YouTube player was changed from a 4:3 aspect ratio to a widescreen 16:9. With this new feature, YouTube began a switchover to H.264/MPEG-4 AVC as its default video compression format. In November 2009, 1080p HD support was added. In July 2010, YouTube announced that it had launched a range of videos in 4K format, which allows a resolution of up to 4096×3072 pixels. In July 2010, support for 2160p UHD was added, with the videos playing at 3840 × 2160 pixels. In June 2014, YouTube began to deploy support for high frame rate videos up to 60 frames per second (as opposed to 30 before), becoming available for user uploads in October. YouTube stated that this would enhance "motion-intensive" videos, such as video game footage. In June 2015, support for 8K resolution was added, with the videos playing at 7680×4320 pixels. In November 2016, support for HDR video was added which can be encoded with hybrid log–gamma (HLG) or perceptual quantizer (PQ). HDR video can be encoded with the Rec. 2020 color space.
YouTube videos are available in a range of quality levels. Viewers only indirectly influence the video quality. In the mobile apps, users choose between "Auto", which adjusts resolution based on the internet connection, "High Picture Quality" which will prioritize playing high-quality video, "Data saver" which will sacrifice video quality in favor of low data usage and "Advanced" which lets the user choose a stream resolution. On desktop, users choose between "Auto" and a specific resolution. It is not possible for the viewer to directly choose a higher bitrate (quality) for any selected resolution.
Since 2009, viewers have had the ability to watch 3D videos. In 2015, YouTube began natively supporting 360-degree video. Since April 2016, it allowed live streaming 360° video, and both normal and 360° video at up to 1440p, and since November 2016 both at up to 4K (2160p) resolution. Citing the limited number of users who watched more than 90-degrees, it began supporting an alternative stereoscopic video format known as VR180 which it said was easier to produce, which allows users to watch any video using virtual reality headsets.
In response to increased viewership during the COVID-19 pandemic, YouTube temporarily downgraded the quality of its videos. YouTube developed its own chip, called "Argos", to help with encoding higher resolution videos in 2021.
In April 2023, YouTube began offering some videos in an enhanced bitrate "1080p Premium" option for YouTube Premium subscribers on iOS. In August 2023, the feature became available to subscribers on desktop platforms.
In certain cases, YouTube allows the uploader to upgrade the quality of videos uploaded a long time ago in poor quality. One such partnership with Universal Music Group included remasters of 1,000 music videos.
==== Live streaming ====
YouTube carried out early experiments with live streaming, including its YouTube Live event in 2008, a concert by U2 in 2009, and a question-and-answer session with US President Barack Obama in February 2010. These tests had relied on technology from 3rd-party partners, but in September 2010, YouTube began testing its own live streaming infrastructure. In April 2011, YouTube announced the rollout of YouTube Live. The creation of live streams was initially limited to select partners. It was used for real-time broadcasting of events such as the 2012 Olympics in London. In October 2012, more than 8 million people watched Felix Baumgartner's jump from the edge of space as a live stream on YouTube.
In May 2013, creation of live streams was opened to verified users with at least 1,000 subscribers; in August of the same year the number was reduced to 100 subscribers, and in December the limit was removed. In February 2017, live streaming was introduced to the official YouTube mobile app. Live streaming via mobile was initially restricted to users with at least 10,000 subscribers, but as of mid-2017 it has been reduced to 100 subscribers. Live streams support HDR, can be up to 4K resolution at 60 fps, and also support 360° video.
=== User features ===
==== Comment system ====
Most videos enable users to leave comments, which have attracted attention for the negative aspects of their form and content. In 2006, Time praised Web 2.0 for enabling "community and collaboration on a scale never seen before", and added that YouTube "harnesses the stupidity of crowds as well as its wisdom. Some of the comments on YouTube make you weep for the future of humanity just for the spelling alone, never mind the obscenity and the naked hatred". The Guardian in 2009 described users' comments on YouTube as:
Juvenile, aggressive, misspelt, sexist, homophobic, swinging from raging at the contents of a video to providing a pointlessly detailed description followed by a LOL, YouTube comments are a hotbed of infantile debate and unashamed ignorance—with the occasional burst of wit shining through.
The Daily Telegraph commented in September 2008, that YouTube was "notorious" for "some of the most confrontational and ill-formed comment exchanges on the internet", and reported on YouTube Comment Snob, "a new piece of software that blocks rude and illiterate posts". The Huffington Post noted in April 2012 that finding comments on YouTube that appear "offensive, stupid and crass" to the "vast majority" of the people is hardly difficult.
Google subsequently implemented a comment system oriented on Google+ on November 6, 2013, that required all YouTube users to use a Google+ account to comment on videos. The stated motivation for the change was giving creators more power to moderate and block comments, thereby addressing frequent criticisms of their quality and tone. The new system restored the ability to include URLs in comments, which had previously been removed due to problems with abuse. In response, YouTube co-founder Jawed Karim posted the question "why the fuck do I need a google+ account to comment on a video?" on his YouTube channel to express his negative opinion of the change. The official YouTube announcement received 20,097 "thumbs down" votes and generated more than 32,000 comments in two days. Writing in the Newsday blog Silicon Island, Chase Melvin noted that "Google+ is nowhere near as popular a social media network like Facebook, but it's essentially being forced upon millions of YouTube users who don't want to lose their ability to comment on videos" and added that "Discussion forums across the Internet are already bursting with the outcry against the new comment system". In the same article Melvin goes on to say:
Perhaps user complaints are justified, but the idea of revamping the old system isn't so bad.
Think of the crude, misogynistic and racially-charged mudslinging that has transpired over the last eight years on YouTube without any discernible moderation. Isn't any attempt to curb unidentified libelers worth a shot? The system is far from perfect, but Google should be lauded for trying to alleviate some of the damage caused by irate YouTubers hiding behind animosity and anonymity.
Later, on July 27, 2015, Google announced in a blog post that it would be removing the requirement to sign up to a Google+ account to post comments to YouTube. On November 3, 2016, YouTube announced a trial scheme which allows the creators of videos to decide whether to approve, hide or report the comments posted on videos based on an algorithm that detects potentially offensive comments. Creators may also choose to keep or delete comments with links or hashtags to combat spam. They can also allow other users to moderate their comments.
In December 2020, it was reported that YouTube would launch a new feature that will warn users who post a comment that "may be offensive to others."
==== Community ====
On September 13, 2016, YouTube launched a public beta of Community, a social media-based feature that allows users to post text, images (including GIFs), live videos and others in a separate "Community" tab on their channel. Prior to the release, several creators had been consulted to suggest tools Community could incorporate that they would find useful; these YouTubers included Vlogbrothers, AsapScience, Lilly Singh, The Game Theorists, Karmin, The Key of Awesome, The Kloons, Peter Hollens, Rosianna Halse Rojas, Sam Tsui, Threadbanger and Vsauce3.
After the feature has been officially released, the community post feature gets activated automatically for every channel that passes a specific threshold of subscriber counts or already has more subscribers. This threshold was lowered over time, from 10,000 subscribers to 1500 subscribers, to 1000 subscribers, to 500 subscribers.
Channels that the community tab becomes enabled for, get their channel discussions (previously known as channel comments) permanently erased, instead of co-existing or migrating.
==== TestTube ====
Experimental features of YouTube could be accessed in an area of the site formerly named TestTube.
For example, in October 2009, a comment search feature accessible under /comment_search was implemented as part of this program. The feature was removed later. Later the same year, YouTube Feather was introduced as a "lightweight" alternative website for countries with limited internet speeds. Following the transition to the Polymer layout, TestTube was disabled, and the URL redirects to video playback settings. TestTube was replaced by a new system that requires users to be premium members to enable or disable experiments.
=== Content accessibility ===
YouTube offers users the ability to view its videos on web pages outside their website. Each YouTube video is accompanied by a piece of HTML that can be used to embed it on any page on the Web. This functionality is often used to embed YouTube videos in social networking pages and blogs. Users wishing to post a video discussing, inspired by, or related to another user's video can make a "video response". The eleven character YouTube video identifier (64 possible characters used in each position), allows for a theoretical maximum of 6411 or around 73.8 quintillion (73.8 billion billion) unique ids.
YouTube announced that it would remove video responses for being an underused feature on August 27, 2013. Embedding, rating, commenting and response posting can be disabled by the video owner. YouTube does not usually offer a download link for its videos, and intends for them to be viewed through its website interface. A small number of videos can be downloaded as MP4 files. Numerous third-party web sites, applications and browser plug-ins allow users to download YouTube videos.
In February 2009, YouTube announced a test service, allowing some partners to offer video downloads for free or for a fee paid through Google Checkout. In June 2012, Google sent cease and desist letters threatening legal action against several websites offering online download and conversion of YouTube videos. In response, Zamzar removed the ability to download YouTube videos from its site. Users retain copyright of their own work under the default Standard YouTube License, but have the option to grant certain usage rights under any public copyright license they choose.
Since July 2012, it has been possible to select a Creative Commons attribution license as the default, allowing other users to reuse and remix the material.
==== Platforms ====
Most modern smartphones are capable of accessing YouTube videos, either within an application or through an optimized website. YouTube Mobile was launched in June 2007, using RTSP streaming for the video. Not all of YouTube's videos are available on the mobile version of the site.
Since June 2007, YouTube's videos have been available for viewing on a range of Apple products. This required YouTube's content to be transcoded into Apple's preferred video standard, H.264, a process that took several months. YouTube videos can be viewed on devices including Apple TV, iPod Touch and the iPhone.
The mobile version of the site was relaunched based on HTML video in July 2010, avoiding the need to use Adobe Flash Player and optimized for use with touch screen controls. The mobile version is also available as an app for the Android platform.
In September 2012, YouTube launched its first app for the iPhone, following the decision to drop YouTube as one of the preloaded apps in the iPhone 5 and iOS 6 operating system. According to GlobalWebIndex, YouTube was used by 35% of smartphone users between April and June 2013, making it the third-most used app.
A TiVo service update in July 2008 allowed the system to search and play YouTube videos.
In January 2009, YouTube launched "YouTube for TV", a version of the website tailored for set-top boxes and other TV-based media devices with web browsers, initially allowing its videos to be viewed on the PlayStation 3 and Wii video game consoles.
During the month of June that same year, YouTube XL was introduced, which has a simplified interface designed for viewing on a standard television screen. YouTube is also available as an app on Xbox Live.
On November 15, 2012, Google launched an official app for the Wii, allowing users to watch YouTube videos from the Wii channel. An app was available for Wii U and Nintendo 3DS, but was discontinued in August 2019. Videos can also be viewed on the Wii U Internet Browser using HTML video. Google made YouTube available on the Roku player on December 17, 2013, and, in October 2014, the Sony PlayStation 4.
YouTube launched as a downloadable app for the Nintendo Switch in November 2018.
=== International and localization ===
In early years of operation, Google faced some criticism for 'encouraging the dominance of US values', by prioritising English over other languages. On June 19, 2007, at a conference in Paris, Google CEO Eric Schmidt launched YouTube localization, with stated aims including customizing the YouTube experience by country, including country-specific comments, metrics, and video rankings. From 2007, YouTube's localization was rolled out.
A 2015 report on YouTube's localization showed it to be continuing, and expanding. In February 2023, YouTube made it possible to upload a single video in multiple languages. Prior to 2023, the only option for YouTubers to broaden their content's reach to audiences speaking different languages was to launch an entirely separate secondary channel for each language and upload dubbed versions of their videos across all those channels. MrBeast called multi-language dub tracks a “giant win” for creators. With the introduction of the dubbing localization option, many creators switched from uploading to separate channels to uploading to their main channel with dubbed versions.
==== YouTube localization by country ====
As of 2024, the interface of YouTube is available with localized versions in 104 countries, one territory (Hong Kong) and a worldwide version and continues to extend the availability of its localized version to additional countries and regions.
If YouTube is unable to identify a specific country or region according to the IP address, the default location is the United States. However, YouTube offers language and content preferences for all accessible countries, regions, and languages.
The YouTube interface suggests which local version should be chosen based on the IP address of the user. In some cases, the message "This video is not available in your country" may appear because of copyright restrictions or inappropriate content. The interface of the YouTube website is available in 76 language versions, including Amharic, Albanian, Armenian, Burmese, Haitian Creole, Kyrgyz, Malagasy, Mongolian, Persian, Samoan, Somali and Uzbek, which do not have local channel versions. Access to YouTube was blocked in Turkey between 2008 and 2010, following controversy over the posting of videos deemed insulting to Mustafa Kemal Atatürk and some material offensive to Muslims. In October 2012, a local version of YouTube was launched in Turkey, with the domain youtube.com.tr. The local version is subject to the content regulations found in Turkish law. In March 2009, a dispute between YouTube and the British royalty collection agency PRS for Music led to premium music videos being blocked for YouTube users in the United Kingdom. The removal of videos posted by the major record companies occurred after failure to reach an agreement on a licensing deal. The dispute was resolved in September 2009. In April 2009, a similar dispute led to the removal of premium music videos for users in Germany.
== Videos ==
In January 2012, it was estimated that visitors to YouTube spent an average of 15 minutes a day on the site, in contrast to the four or five hours a day spent by a typical US citizen watching television. In 2017, viewers on average watched YouTube on mobile devices for more than an hour every day.
In December 2012, two billion views were removed from the view counts of Universal and Sony music videos on YouTube, prompting a claim by The Daily Dot that the views had been deleted due to a violation of the site's terms of service, which ban the use of automated processes to inflate view counts. This was disputed by Billboard, which said that the two billion views had been moved to Vevo, since the videos were no longer active on YouTube. On August 5, 2015, YouTube patched the formerly notorious behavior which caused a video's view count to freeze at "301" (later "301+") until the actual count was verified to prevent view count fraud. YouTube view counts once again updated in real time.
Since September 2019, subscriber counts are abbreviated. Only three leading digits of channels' subscriber counts are indicated publicly, compromising the function of third-party real-time indicators such as that of Social Blade. Exact counts remain available to channel operators inside YouTube Studio.
On November 11, 2021, after testing out this change in March of the same year, YouTube announced it would start hiding dislike counts on videos, making them invisible to viewers. The company stated the decision was in response to experiments which confirmed that smaller YouTube creators were more likely to be targeted in dislike brigading and harassment. Creators will still be able to see the number of likes and dislikes in the YouTube Studio dashboard tool, according to YouTube.
=== Copyright issues ===
YouTube has faced numerous challenges and criticisms in its attempts to deal with copyright, including the site's first viral video, Lazy Sunday, which had to be taken down, due to copyright concerns. At the time of uploading a video, YouTube users are shown a message asking them not to violate copyright laws. Despite this advice, many unauthorized clips of copyrighted material remain on YouTube. YouTube does not view videos before they are posted online, and it is left to copyright holders to issue a DMCA takedown notice pursuant to the terms of the Online Copyright Infringement Liability Limitation Act. Any successful complaint about copyright infringement results in a YouTube copyright strike. Three successful complaints for copyright infringement against a user account will result in the account and all of its uploaded videos being deleted. From 2007 to 2009 organizations including Viacom, Mediaset, and the English Premier League have filed lawsuits against YouTube, claiming that it has done too little to prevent the uploading of copyrighted material.
In August 2008, a US court ruled in Lenz v. Universal Music Corp. that copyright holders cannot order the removal of an online file without first determining whether the posting reflected fair use of the material. YouTube's owner Google announced in November 2015 that they would help cover the legal cost in select cases where they believe fair use defenses apply.
In the 2011 case of Smith v. Summit Entertainment LLC, professional singer Matt Smith sued Summit Entertainment for the wrongful use of copyright takedown notices on YouTube. He asserted seven causes of action, and four were ruled in Smith's favor. In April 2012, a court in Hamburg ruled that YouTube could be held responsible for copyrighted material posted by its users. On November 1, 2016, the dispute with GEMA was resolved, with Google content ID being used to allow advertisements to be added to videos with content protected by GEMA.
In April 2013, it was reported that Universal Music Group and YouTube have a contractual agreement that prevents content blocked on YouTube by a request from UMG from being restored, even if the uploader of the video files a DMCA counter-notice. As part of YouTube Music, Universal and YouTube signed an agreement in 2017, which was followed by separate agreements other major labels, which gave the company the right to advertising revenue when its music was played on YouTube. By 2019, creators were having videos taken down or demonetized when Content ID identified even short segments of copyrighted music within a much longer video, with different levels of enforcement depending on the record label. Experts noted that some of these clips said qualified for fair use.
==== Content ID ====
In June 2007, YouTube began trials of a system for automatic detection of uploaded videos that infringe copyright. Google CEO Eric Schmidt regarded this system as necessary for resolving lawsuits such as the one from Viacom, which alleged that YouTube profited from content that it did not have the right to distribute. The system, which was initially called "Video Identification" and later became known as Content ID, creates an ID File for copyrighted audio and video material, and stores it in a database. When a video is uploaded, it is checked against the database, and flags the video as a copyright violation if a match is found. When this occurs, the content owner has the choice of blocking the video to make it unviewable, tracking the viewing statistics of the video, or adding advertisements to the video.
An independent test in 2009 uploaded multiple versions of the same song to YouTube and concluded that while the system was "surprisingly resilient" in finding copyright violations in the audio tracks of videos, it was not infallible. The use of Content ID to remove material automatically has led to controversy in some cases, as the videos have not been checked by a human for fair use. If a YouTube user disagrees with a decision by Content ID, it is possible to fill in a form disputing the decision.
Before 2016, videos were not monetized until the dispute was resolved. Since April 2016, videos continue to be monetized while the dispute is in progress, and the money goes to whoever won the dispute. Should the uploader want to monetize the video again, they may remove the disputed audio in the "Video Manager". YouTube has cited the effectiveness of Content ID as one of the reasons why the site's rules were modified in December 2010 to allow some users to upload videos of unlimited length.
=== Moderation and offensive content ===
YouTube has a set of community guidelines aimed to reduce abuse of the site's features. The uploading of videos containing defamation, pornography, and material encouraging criminal conduct is forbidden by YouTube's "Community Guidelines". Generally prohibited material includes sexually explicit content, videos of animal abuse, shock videos, content uploaded without the copyright holder's consent, hate speech, spam, and predatory behavior. YouTube relies on its users to flag the content of videos as inappropriate, and a YouTube employee will view a flagged video to determine whether it violates the site's guidelines. Despite the guidelines, YouTube has faced criticism over aspects of its operations, its recommendation algorithms perpetuating videos that promote conspiracy theories and falsehoods, hosting videos ostensibly targeting children but containing violent or sexually suggestive content involving popular characters, videos of minors attracting pedophilic activities in their comment sections, and fluctuating policies on the types of content that is eligible to be monetized with advertising.
YouTube contracts companies to hire content moderators, who view content flagged as potentially violating YouTube's content policies and determines if they should be removed. In September 2020, a class-action suit was filed by a former content moderator who reported developing post-traumatic stress disorder (PTSD) after an 18-month period on the job. The former content moderator said that she was regularly made to exceed YouTube's stated limit of four hours per day of viewing graphic content. The lawsuit alleges that YouTube's contractors gave little to no training or support for its moderators' mental health, made prospective employees sign NDAs before showing them any examples of content they would see while reviewing, and censored all mention of trauma from its internal forums. It also purports that requests for extremely graphic content to be blurred, reduced in size or made monochrome, per recommendations from the National Center for Missing and Exploited Children, were rejected by YouTube as not a high priority for the company.
To limit the spread of misinformation and fake news via YouTube, it has rolled out a comprehensive policy regarding how it plans to deal with technically manipulated videos.
Controversial content has included material relating to Holocaust denial and the Hillsborough disaster, in which 96 football fans from Liverpool were crushed to death in 1989. In July 2008, the Culture and Media Committee of the House of Commons of the United Kingdom stated that it was "unimpressed" with YouTube's system for policing its videos, and argued that "proactive review of content should be standard practice for sites hosting user-generated content". YouTube responded by stating:
We have strict rules on what's allowed, and a system that enables anyone who sees inappropriate content to report it to our 24/7 review team and have it dealt with promptly. We educate our community on the rules and include a direct link from every YouTube page to make this process as easy as possible for our users. Given the volume of content uploaded on our site, we think this is by far the most effective way to make sure that the tiny minority of videos that break the rules come down quickly. (July 2008)
In October 2010, U.S. Congressman Anthony Weiner urged YouTube to remove from its website videos of imam Anwar al-Awlaki. YouTube pulled some of the videos in November 2010, stating they violated the site's guidelines. In December 2010, YouTube added the ability to flag videos for containing terrorism content.
In 2018, YouTube introduced a system that would automatically add information boxes to videos that its algorithms determined may present conspiracy theories and other fake news, filling the infobox with content from Encyclopædia Britannica and Wikipedia as a means to inform users to minimize misinformation propagation without impacting freedom of speech. In the wake of the Notre-Dame fire on April 15, 2019, several user-uploaded videos of the landmark fire were flagged by YouTube' system automatically with an Encyclopædia Britannica article on the false conspiracy theories around the September 11 attacks. Several users complained to YouTube about this inappropriate connection. YouTube officials apologized for this, stating that their algorithms had misidentified the fire videos and added the information block automatically, and were taking steps to remedy this.
On April 18, 2023, YouTube revealed its changes in handling content associated with eating disorders. This social media platform's Community Guidelines now prohibit content that could encourage emulation from at-risk users. This content includes behavior that shows severe calorie tracking and purging after eating. However, videos featuring positive behavior such as in the context of recovery will be permitted on the platform under two conditions—the user must have a registered (logged-in) account and must be older than 18.
This policy was created in collaboration with nonprofit organizations as well as the National Eating Disorder Association. Garth Graham, YouTube's Global Head of Healthcare revealed in an interview with CNN that this policy change was geared at ensuring that this video-sharing platform provides an avenue for "community recovery and resources" while ensuring continued viewer protection.
==== Homophobia and transphobia ====
Five leading content creators whose channels were based on LGBTQ+ materials filed a federal lawsuit against YouTube in August 2019, alleging that YouTube's algorithms divert discovery away from their channels, impacting their revenue. The plaintiffs claimed that the algorithms discourage content with words like "lesbian" or "gay", which would be predominant in their channels' content, and because of YouTube's near-monopolization of online video services, they are abusing that position.
In June 2022, Media Matters, a media watchdog group, reported that homophobic and transphobic content calling LGBT people "predators" and "groomers" was becoming more common on YouTube. The report also referred to common accusations in YouTube videos that LGBT people are mentally ill. The report stated the content appeared to be in violation of YouTube's hate speech policy.
==== Animal torture ====
From 2020 on, the issue of videos featuring animal cruelty on YouTube has started to attract increasing attention in the media. In late 2020, animal welfare charity Lady Freethinker identified 2,053 videos on YouTube in which they stated animals were "deliberately harmed for entertainment or were shown to be under severe psychological distress, physical pain or dead."
In 2021, Lady Freethinker filed a lawsuit accusing YouTube of a breach of contract in allowing a large number of videos on its site showing animal abuse and failing to remove them when notified. YouTube responded by stating that they had "expanded its policy on animal abuse videos" in 2021, and since the introduction of the new policy "removed hundreds of thousands of videos and terminated thousands of channels for violations."
In 2022, Google defeated the Lady Freethinker lawsuit, with a judge ruling that YouTube was protected by Section 230 of the Communications Decency Act, that shields internet platforms from lawsuits based on content posted by their users.
In 2023, YouTube stated that animal abuse "has no place on their platforms, and they are working to remove content (of that nature)".
==== YouTube as a tool to promote conspiracy theories and far-right content ====
YouTube has been criticized for using an algorithm that gives great prominence to videos that promote conspiracy theories, falsehoods and incendiary fringe discourse. According to an investigation by The Wall Street Journal, "YouTube's recommendations often lead users to channels that feature conspiracy theories, partisan viewpoints and misleading videos, even when those users haven't shown interest in such content. When users show a political bias in what they choose to view, YouTube typically recommends videos that echo those biases, often with more-extreme viewpoints." When users search for political or scientific terms, YouTube's search algorithms often give prominence to hoaxes and conspiracy theories. After YouTube drew controversy for giving top billing to videos promoting falsehoods and conspiracy when people made breaking-news queries during the 2017 Las Vegas shooting, YouTube changed its algorithm to give greater prominence to mainstream media sources. In 2018, it was reported that YouTube was again promoting fringe content about breaking news, giving great prominence to conspiracy videos about Anthony Bourdain's death.
In 2017, it was revealed that advertisements were being placed on extremist videos, including videos by rape apologists, anti-Semites, and hate preachers who received ad payouts. After firms started to stop advertising on YouTube in the wake of this reporting, YouTube apologized and said that it would give firms greater control over where ads got placed.
Alex Jones, known for far-right conspiracy theories, had built a massive audience on YouTube. YouTube drew criticism in 2018 when it removed a video from Media Matters compiling offensive statements made by Jones, stating that it violated its policies on "harassment and bullying". On August 6, 2018, however, YouTube removed Alex Jones' YouTube page following a content violation.
University of North Carolina professor Zeynep Tufekci has referred to YouTube as "The Great Radicalizer", saying "YouTube may be one of the most powerful radicalizing instruments of the 21st century." Jonathan Albright of the Tow Center for Digital Journalism at Columbia University described YouTube as a "conspiracy ecosystem".
In January 2019, YouTube said that it had introduced a new policy starting in the United States intended to stop recommending videos containing "content that could misinform users in harmful ways." YouTube gave flat earth theories, miracle cures, and 9/11 truther-isms as examples. Efforts within YouTube engineering to stop recommending borderline extremist videos falling just short of forbidden hate speech, and track their popularity were originally rejected because they could interfere with viewer engagement.
In January 2019, the site announced it would be implementing measures directed towards "raising authoritative content and reducing borderline content and harmful misinformation." That June, YouTube announced it would be banning Holocaust denial and neo-Nazi content. YouTube has blocked the neo-Nazi propaganda film Europa: The Last Battle from being uploaded.
Multiple research studies have investigated cases of misinformation in YouTube. In a July 2019 study based on ten YouTube searches using the Tor Browser related to climate and climate change, the majority of videos were videos that communicated views contrary to the scientific consensus on climate change. A May 2023 study found that YouTube was monetizing and profiting from videos that included misinformation about climate change. A 2019 BBC investigation of YouTube searches in ten different languages found that YouTube's algorithm promoted health misinformation, including fake cancer cures. In Brazil, YouTube has been linked to pushing pseudoscientific misinformation on health matters, as well as elevated far-right fringe discourse and conspiracy theories. In the Philippines, numerous channels disseminated misinformation related to the 2022 Philippine elections. Additionally, research on the dissemination of Flat Earth beliefs in social media, has shown that networks of YouTube channels form an echo chamber that polarizes audiences by appearing to confirm preexisting beliefs.
==== Use among white supremacists ====
Before 2019, YouTube took steps to remove specific videos or channels related to supremacist content that had violated its acceptable use policies but otherwise did not have site-wide policies against hate speech.
In the wake of the March 2019 Christchurch mosque attacks, YouTube and other sites like Facebook and Twitter that allowed user-submitted content drew criticism for doing little to moderate and control the spread of hate speech, which was considered to be a factor in the rationale for the attacks. These platforms were pressured to remove such content, but in an interview with The New York Times, YouTube's chief product officer Neal Mohan said that unlike content such as ISIS videos which take a particular format and thus easy to detect through computer-aided algorithms, general hate speech was more difficult to recognize and handle, and thus could not readily take action to remove without human interaction.
In May 2019, YouTube joined an initiative led by France and New Zealand with other countries and tech companies to develop tools to be used to block online hate speech and to develop regulations, to be implemented at the national level, to be levied against technology firms that failed to take steps to remove such speech, though the United States declined to participate. Subsequently, on June 5, 2019, YouTube announced a major change to its terms of service, "specifically prohibiting videos alleging that a group is superior in order to justify discrimination, segregation or exclusion based on qualities like age, gender, race, caste, religion, sexual orientation or veteran status." YouTube identified specific examples of such videos as those that "promote or glorify Nazi ideology, which is inherently discriminatory". YouTube further stated it would "remove content denying that well-documented violent events, like the Holocaust or the shooting at Sandy Hook Elementary, took place."
In August 2019, the channel of the white nationalist website VDARE was banned. The ban was later reversed. The channel was permanently banned in August 2020 for violating YouTube's policies against hate speech.
In October 2019, YouTube banned the main channel of Red Ice, a white supremacist multimedia company, for hate speech violations. The channel had about 330,000 subscribers. Lana Lokteff and Red Ice promoted a backup channel in an attempt to circumvent the ban. A week later, the backup channel was also removed by YouTube.
In June 2020, YouTube was criticized for allowing white supremacist content on its platform for years after it announced it would be pledging $1 million to fight racial injustice. Later that month, it banned several channels associated with white supremacy, including those of Stefan Molyneux, David Duke, and Richard B. Spencer, asserting these channels violated their policies on hate speech. The ban occurred the same day that Reddit announced the ban on several hate speech sub-forums including r/The Donald.
==== Handling of COVID-19 pandemic and other misinformation ====
Following the dissemination via YouTube of misinformation related to the COVID-19 pandemic that 5G communications technology was responsible for the spread of coronavirus disease 2019 which led to multiple 5G towers in the United Kingdom being attacked by arsonists, YouTube removed all such videos linking 5G and the coronavirus in this manner.
In September 2021, YouTube extended this policy to cover videos disseminating misinformation related to any vaccine, including those long approved against measles or Hepatitis B, that had received approval from local health authorities or the World Health Organization. The platform proceeded to remove the accounts of anti-vaccine campaigners such as Robert F. Kennedy Jr. and Joseph Mercola.
YouTube had extended this moderation to non-medical areas. In the weeks following the 2020 United States presidential election, the site added policies to remove or label videos promoting election fraud claims; however, it reversed this policy in June 2023, citing that the removal was necessary to "openly debate political ideas, even those that are controversial or based on disproven assumptions".
Google and YouTube implemented policies in October 2021 to deny monetization or revenue to advertisers or content creators that promoted climate change denial, which "includes content referring to climate change as a hoax or a scam, claims denying that long-term trends show the global climate is warming, and claims denying that greenhouse gas emissions or human activity contribute to climate change." In January 2024, the Center for Countering Digital Hate reported that climate change deniers were instead pushing other forms of climate change denial that have not yet been banned by YouTube, including false claims that global warming is "beneficial or harmless", and which undermined climate solutions and climate science.
In July 2022, YouTube announced policies to combat misinformation surrounding abortion, such as videos with instructions to perform abortion methods that are considered unsafe and videos that contain misinformation about the safety of abortion.
==== Child safety and wellbeing ====
Leading into 2017, there was a significant increase in the number of videos related to children, coupled between the popularity of parents vlogging their family's activities, and previous content creators moving away from content that often was criticized or demonetized into family-friendly material. In 2017, YouTube reported that time watching family vloggers had increased by 90%. However, with the increase in videos featuring children, the site began to face several controversies related to child safety. During Q2 2017, the owners of popular channel FamilyOFive, which featured themselves playing "pranks" on their children, were accused of child abuse. Their videos were eventually deleted, and two of their children were removed from their custody. A similar case happened in 2019 when the owner of the channel Fantastic Adventures was accused of abusing her adopted children. Her videos would later be deleted.
Later that year, YouTube came under criticism for showing inappropriate videos targeted at children and often featuring popular characters in violent, sexual or otherwise disturbing situations, many of which appeared on YouTube Kids and attracted millions of views. The term "Elsagate" was coined on the Internet and then used by various news outlets to refer to this controversy. On November 11, 2017, YouTube announced it was strengthening site security to protect children from unsuitable content. Later that month, the company started to mass delete videos and channels that made improper use of family-friendly characters. As part of a broader concern regarding child safety on YouTube, the wave of deletions also targeted channels that showed children taking part in inappropriate or dangerous activities under the guidance of adults. Most notably, the company removed Toy Freaks, a channel with over 8.5 million subscribers, that featured a father and his two daughters in odd and upsetting situations. According to analytics specialist SocialBlade, it earned up to $11.2 million annually prior to its deletion in November 2017.
Even for content that appears to be aimed at children and appears to contain only child-friendly content, YouTube's system allows for anonymity of who uploads these videos. These questions have been raised in the past, as YouTube has had to remove channels with children's content which, after becoming popular, then suddenly include inappropriate content masked as children's content. Alternative, some of the most-watched children's programming on YouTube comes from channels that have no identifiable owners, raising concerns of intent and purpose. One channel that had been of concern was "Cocomelon" which provided numerous mass-produced animated videos aimed at children. Up through 2019, it had drawn up to US$10 million a month in ad revenue and was one of the largest kid-friendly channels on YouTube before 2020. Ownership of Cocomelon was unclear outside of its ties to "Treasure Studio", itself an unknown entity, raising questions as to the channel's purpose, but Bloomberg News had been able to confirm and interview the small team of American owners in February 2020 regarding "Cocomelon", who stated their goal for the channel was to simply entertain children, wanting to keep to themselves to avoid attention from outside investors. The anonymity of such channel raise concerns because of the lack of knowledge of what purpose they are trying to serve. The difficulty to identify who operates these channels "adds to the lack of accountability", according to Josh Golin of the Campaign for a Commercial-Free Childhood, and educational consultant Renée Chernow-O'Leary found the videos were designed to entertain with no intent to educate, all leading to critics and parents to be concerned for their children becoming too enraptured by the content from these channels. Content creators that earnestly make child-friendly videos have found it difficult to compete with larger channels, unable to produce content at the same rate as them, and lacking the same means of being promoted through YouTube's recommendation algorithms that the larger animated channel networks have shared.
In January 2019, YouTube officially banned videos containing "challenges that encourage acts that have an inherent risk of severe physical harm" (such as the Tide Pod Challenge) and videos featuring pranks that "make victims believe they're in physical danger" or cause emotional distress in children.
==== Sexualization of children and pedophilia ====
Also in November 2017, it was revealed in the media that many videos featuring children—often uploaded by the minors themselves, and showing innocent content such as the children playing with toys or performing gymnastics—were attracting comments from pedophiles with predators finding the videos through private YouTube playlists or typing in certain keywords in Russian. Other child-centric videos originally uploaded to YouTube began propagating on the dark web, and uploaded or embedded onto forums known to be used by pedophiles.
As a result of the controversy, which added to the concern about "Elsagate", several major advertisers whose ads had been running against such videos froze spending on YouTube. In December 2018, The Times found more than 100 grooming cases in which children were manipulated into sexually implicit behavior (such as taking off clothes, adopting overtly sexual poses and touching other children inappropriately) by strangers. After a reporter flagged the videos in question, half of them were removed, and the rest were removed after The Times contacted YouTube's PR department.
In February 2019, YouTube vlogger Matt Watson identified a "wormhole" that would cause the YouTube recommendation algorithm to draw users into this type of video content, and make all of that user's recommended content feature only these types of videos. Most of these videos had comments from sexual predators commenting with timestamps of when the children were shown in compromising positions or otherwise making indecent remarks. In some cases, other users had re-uploaded the video in unlisted form but with incoming links from other videos, and then monetized these, propagating this network. In the wake of the controversy, the service reported that they had deleted over 400 channels and tens of millions of comments, and reported the offending users to law enforcement and the National Center for Missing and Exploited Children. A spokesperson explained that "any content—including comments—that endangers minors is abhorrent and we have clear policies prohibiting this on YouTube. There's more to be done, and we continue to work to improve and catch abuse more quickly." Despite these measures, AT&T, Disney, Dr. Oetker, Epic Games, and Nestlé all pulled their advertising from YouTube.
Subsequently, YouTube began to demonetize and block advertising on the types of videos that have drawn these predatory comments. The service explained that this was a temporary measure while they explore other methods to eliminate the problem. YouTube also began to flag channels that predominantly feature children, and preemptively disable their comments sections. "Trusted partners" can request that comments be re-enabled, but the channel will then become responsible for moderating comments. These actions mainly target videos of toddlers, but videos of older children and teenagers may be protected as well if they contain actions that can be interpreted as sexual, such as gymnastics. YouTube stated it was also working on a better system to remove comments on other channels that matched the style of child predators.
A related attempt to algorithmically flag videos containing references to the string "CP" (an abbreviation of child pornography) resulted in some prominent false positives involving unrelated topics using the same abbreviation, including videos related to the mobile video game Pokémon Go (which uses "CP" as an abbreviation of the statistic "Combat Power"), and Club Penguin. YouTube apologized for the errors and reinstated the affected videos. Separately, online trolls have attempted to have videos flagged for takedown or removal by commenting with statements similar to what the child predators had said; this activity became an issue during the PewDiePie vs T-Series rivalry in early 2019. YouTube stated they do not take action on any video with these comments but those that they have flagged that are likely to draw child predator activity.
In June 2019, The New York Times cited researchers who found that users who watched erotic videos could be recommended seemingly innocuous videos of children. As a result, Senator Josh Hawley stated plans to introduce federal legislation that would ban YouTube and other video sharing sites from including videos that predominantly feature minors as "recommended" videos, excluding those that were "professionally produced", such as videos of televised talent shows. YouTube has suggested potential plans to remove all videos featuring children from the main YouTube site and transferring them to the YouTube Kids site where they would have stronger controls over the recommendation system, as well as other major changes on the main YouTube site to the recommended feature and auto-play system.
==== Misogyny ====
An August 2022 report by the Center for Countering Digital Hate, a British think tank, found that harassment against women was flourishing on YouTube. It noted that channels espousing a similar ideology to that of men's rights influencer Andrew Tate were using YouTube to grow their audience, despite Tate being banned from the platform. In his 2022 book Like, Comment, Subscribe: Inside YouTube's Chaotic Rise to World Domination, Bloomberg reporter Mark Bergen said that many female content creators were dealing with harassment, bullying, and stalking.
=== Russia ===
In 2021, two accounts linked to RT Deutsch, the German channel of the Russian RT network were removed as well for breaching YouTube's policies relating to COVID-19. Russia threatened to ban YouTube after the platform deleted two German RT channels in September 2021.
Shortly after the Russian invasion of Ukraine in 2022, YouTube removed all channels funded by the Russian state. YouTube expanded the removal of Russian content from its site to include channels described as 'pro-Russian'. In June 2022, the War Gonzo channel run by Russian military blogger and journalist Semyon Pegov was deleted. In July 2023, YouTube removed the channel of British journalist Graham Phillips, active in covering the War in Donbas from 2014.
In August 2023, a Moscow court fined Google 3 million rubles, around $35,000, for not deleting what it said was "fake news about the war in Ukraine".
=== April Fools gags ===
YouTube featured an April Fools prank on the site on April 1 of every year from 2008 to 2016. In 2008, all links to videos on the main page were redirected to Rick Astley's music video "Never Gonna Give You Up", a prank known as "rickrolling". The next year, when clicking on a video on the main page, the whole page turned upside down, which YouTube claimed was a "new layout". In 2010, YouTube temporarily released a "TEXTp" mode which rendered video imagery into ASCII art letters "in order to reduce bandwidth costs by $1 per second."
The next year, the site celebrated its "100th anniversary" with a range of sepia-toned silent, early 1900s-style films, including a parody of Keyboard Cat. In 2012, clicking on the image of a DVD next to the site logo led to a video about a purported option to order every YouTube video for home delivery on DVD.
In 2013, YouTube teamed up with satirical newspaper company The Onion to claim in an uploaded video that the video-sharing website was launched as a contest which had finally come to an end, and would shut down for ten years before being re-launched in 2023, featuring only the winning video. The video starred several YouTube celebrities, including Antoine Dodson. A video of two presenters announcing the nominated videos streamed live for 12 hours.
In 2014, YouTube announced that it was responsible for the creation of all viral video trends, and revealed previews of upcoming trends, such as "Clocking", "Kissing Dad", and "Glub Glub Water Dance". The next year, YouTube added a music button to the video bar that played samples from "Sandstorm" by Darude. In 2016, YouTube introduced an option to watch every video on the platform in 360-degree mode with Snoop Dogg.
== Services ==
=== YouTube Premium ===
YouTube Premium (formerly YouTube Red) is YouTube's premium subscription service. It offers advertising-free streaming, access to original programming, and background and offline video playback on mobile devices. YouTube Premium was originally announced on November 12, 2014, as "Music Key", a subscription music streaming service, and was intended to integrate with and replace the existing Google Play Music "All Access" service. On October 28, 2015, the service was relaunched as YouTube Red, offering ad-free streaming of all videos and access to exclusive original content. As of November 2016, the service has 1.5 million subscribers, with a further million on a free-trial basis. As of June 2017, the first season of YouTube Originals had received 250 million views in total.
=== YouTube Kids ===
YouTube Kids is an American children's video app developed by YouTube, a subsidiary of Google. The app was developed in response to parental and government scrutiny on the content available to children. The app provides a version of the service-oriented towards children, with curated selections of content, parental control features, and filtering of videos deemed inappropriate viewing for children aged under 13, 8 or 5 depending on the age grouping chosen. First released on February 15, 2015, as an Android and iOS mobile app, the app has since been released for LG, Samsung, and Sony smart TVs, as well as for Android TV. On May 27, 2020, it became available on Apple TV. As of September 2019, the app is available in 69 countries, including Hong Kong and Macau, and one province. YouTube launched a web-based version of YouTube Kids on August 30, 2019.
=== YouTube Music ===
On September 28, 2016, YouTube named Lyor Cohen, the co-founder of 300 Entertainment and former Warner Music Group executive, the Global Head of Music.
In early 2018, Cohen began hinting at the possible launch of YouTube's new subscription music streaming service, a platform that would compete with other services such as Spotify and Apple Music. On May 22, 2018, the music streaming platform named "YouTube Music" was launched.
=== YouTube Movies & TV ===
YouTube Movies & TV is a video on demand service that offers movies and television shows for purchase or rental, depending on availability, along with a selection of movies (encompassing between 100 and 500 titles overall) that are free to stream, with interspersed ad breaks. YouTube began offering free-to-view movie titles to its users in November 2018; selections of new movies are added and others removed, unannounced each month.
In March 2021, Google announced plans to gradually deprecate the Google Play Movies & TV app, and eventually migrate all users to the YouTube app's Movies & TV store to view, rent and purchase movies and TV shows (first affecting Roku, Samsung, LG, and Vizio smart TV users on July 15). Google Play Movies & TV formally shut down on January 17, 2024, with the web version of that platform migrated to YouTube as an expansion of the Movies & TV store to desktop users. (Other functions of Google Play Movies & TV were integrated into the Google TV service.)
==== YouTube Primetime Channels ====
On November 1, 2022, YouTube launched Primetime Channels, a channel store platform offering third-party subscription streaming add-ons sold a la carte through the YouTube website and app, competing with similar subscription add-on stores operated by Apple, Prime Video and Roku. The add-ons can be purchased through the YouTube Movies & TV hub or through the official YouTube channels of the available services; subscribers of YouTube TV add-ons that are sold through Primetime Channels can also access their content via the YouTube app and website. A total of 34 streaming services (including Paramount+, Showtime, Starz, MGM+, AMC+ and ViX+) were initially available for purchase.
NFL Sunday Ticket, as part of a broader residential distribution deal with Google signed in December 2022 that also made it available to YouTube TV subscribers, was added to Primetime Channels as a standalone add-on on August 16, 2023. The ad-free tier of Max was added to Primetime Channels on December 12, 2023, coinciding with YouTube TV converting its separate HBO (for base plan subscribers) and HBO Max (for all subscribers) linear/VOD add-ons into a single combined Max offering.
=== YouTube TV ===
On February 28, 2017, in a press announcement held at YouTube Space Los Angeles, YouTube announced YouTube TV, an over-the-top MVPD-style subscription service that would be available for United States customers at a price of US$65 per month. Initially launching in five major markets (New York City, Los Angeles, Chicago, Philadelphia and San Francisco) on April 5, 2017, the service offers live streams of programming from the five major broadcast networks (ABC, CBS, The CW, Fox and NBC, along with selected MyNetworkTV affiliates and independent stations in certain markets), as well as approximately 60 cable channels owned by companies such as The Walt Disney Company, Paramount Global, Fox Corporation, NBCUniversal, Allen Media Group and Warner Bros. Discovery (including among others Bravo, USA Network, Syfy, Disney Channel, CNN, Cartoon Network, E!, Fox Sports 1, Freeform, FX and ESPN).
Subscribers can also receive premium cable channels (including HBO (via a combined Max add-on that includes in-app and log-in access to the service), Cinemax, Showtime, Starz and MGM+) and other subscription services (such as NFL Sunday Ticket, MLB.tv, NBA League Pass, Curiosity Stream and Fox Nation) as optional add-ons for an extra fee, and can access YouTube Premium original content. In September 2022, YouTube TV began allowing customers to purchase most of its premium add-ons (excluding certain services such as NBA League Pass and AMC+) without an existing subscription to its base package.
=== YouTube Go ===
In September 2016, YouTube Go was announced, as an Android app created for making YouTube easier to access on mobile devices in emerging markets. It was distinct from the company's main Android app and allowed videos to be downloaded and shared with other users. It also allowed users to preview videos, share downloaded videos through Bluetooth, and offered more options for mobile data control and video resolution.
In February 2017, YouTube Go was launched in India, and expanded in November 2017 to 14 other countries, including Nigeria, Indonesia, Thailand, Malaysia, Vietnam, the Philippines, Kenya, and South Africa. On February 1, 2018, it was rolled out in 130 countries worldwide, including Brazil, Mexico, Turkey, and Iraq. Before it shut down, the app was available to around 60% of the world's population. In May 2022, Google announced that they would be shutting down YouTube Go in August 2022.
=== YouTube Shorts ===
In September 2020, YouTube announced that it would be launching a beta version of a new platform of 15-second videos, similar to TikTok, called YouTube Shorts. The platform was first tested in India but as of March 2021 has expanded to other countries including the United States with videos now able to be up to 1 minute long. The platform is not a standalone app, but is integrated into the main YouTube app. Like TikTok, it gives users access to built-in creative tools, including the possibility of adding licensed music to their videos. The platform had its global beta launch in July 2021.
=== YouTube Stories ===
In 2018, YouTube started testing a new feature initially called "YouTube Reels". The feature was nearly identical to Instagram Stories and Snapchat Stories. YouTube later renamed the feature "YouTube Stories". It was only available to creators who had more than 10,000 subscribers and could only be posted/seen in the YouTube mobile app. On May 25, 2023, YouTube announced that they would be shutting down this feature on June 26, 2023.
=== YouTube VR ===
In November 2016, YouTube released YouTube VR, a dedicated version with an interface for VR devices, for Google's Daydream mobile VR platform on Android. In November 2018, YouTube VR was released on the Oculus Store for the Oculus Go headset. YouTube VR was updated since for compatibility with successive Quest devices, and was ported to Pico 4.
YouTube VR allows for access to all YouTube-hosted videos, but particularly supports headset access for 360° and 180°-degree video (both in 2D and stereoscopic 3D). Starting with the Oculus Quest, the app was updated for compatibility with mixed-reality passthrough modes on VR headsets. In April 2024, YouTube VR was updated to support 8K SDR video on Meta Quest 3.
== Social impact ==
Private individuals and large production corporations have used YouTube to grow their audiences. Indie creators have built grassroots followings numbering in the thousands at very little cost or effort, while mass retail and radio promotion proved problematic. Concurrently, old media celebrities moved into the website at the invitation of a YouTube management that witnessed early content creators accruing substantial followings and perceived audience sizes potentially larger than that attainable by television. While YouTube's revenue-sharing "Partner Program" made it possible to earn a substantial living as a video producer—its top five hundred partners each earning more than $100,000 annually and its ten highest-earning channels grossing from $2.5 million to $12 million—in 2012 CMU business editor characterized YouTube as "a free-to-use ... promotional platform for the music labels." In 2013 Forbes' Katheryn Thayer asserted that digital-era artists' work must not only be of high quality, but must elicit reactions on the YouTube platform and social media. Videos of the 2.5% of artists categorized as "mega", "mainstream" and "mid-sized" received 90.3% of the relevant views on YouTube and Vevo in that year. By early 2013, Billboard had announced that it was factoring YouTube streaming data into calculation of the Billboard Hot 100 and related genre charts.
Observing that face-to-face communication of the type that online videos convey has been "fine-tuned by millions of years of evolution", TED curator Chris Anderson referred to several YouTube contributors and asserted that "what Gutenberg did for writing, online video can now do for face-to-face communication." Anderson asserted that it is not far-fetched to say that online video will dramatically accelerate scientific advance, and that video contributors may be about to launch "the biggest learning cycle in human history." In education, for example, the Khan Academy grew from YouTube video tutoring sessions for founder Salman Khan's cousin into what Forbes' Michael Noer called "the largest school in the world," with technology poised to disrupt how people learn. YouTube was awarded a 2008 George Foster Peabody Award, the website being described as a Speakers' Corner that "both embodies and promotes democracy." The Washington Post reported that a disproportionate share of YouTube's most subscribed channels feature minorities, contrasting with mainstream television in which the stars are largely white. A Pew Research Center study reported the development of "visual journalism", in which citizen eyewitnesses and established news organizations share in content creation. The study also concluded that YouTube was becoming an important platform by which people acquire news.
YouTube has enabled people to more directly engage with government, such as in the CNN/YouTube presidential debates (2007) in which ordinary people submitted questions to U.S. presidential candidates via YouTube video, with a techPresident co-founder saying that Internet video was changing the political landscape. Describing the Arab Spring (2010–2012), sociologist Philip N. Howard quoted an activist's succinct description that organizing the political unrest involved using "Facebook to schedule the protests, Twitter to coordinate, and YouTube to tell the world." In 2012, more than a third of the U.S. Senate introduced a resolution condemning Joseph Kony 16 days after the "Kony 2012" video was posted to YouTube, with resolution co-sponsor Senator Lindsey Graham remarking that the video "will do more to lead to (Kony's) demise than all other action combined."
Conversely, YouTube has also allowed government to more easily engage with citizens, the White House's official YouTube channel being the seventh top news organization producer on YouTube in 2012 and in 2013 a healthcare exchange commissioned Obama impersonator Iman Crosson's YouTube music video spoof to encourage young Americans to enroll in the Affordable Care Act (Obamacare)-compliant health insurance. In February 2014, U.S. President Obama held a meeting at the White House with leading YouTube content creators not only to promote awareness of Obamacare but more generally to develop ways for government to better connect with the "YouTube Generation." Whereas YouTube's inherent ability to allow presidents to directly connect with average citizens was noted, the YouTube content creators' new media savvy was perceived necessary to better cope with the website's distracting content and fickle audience.
Some YouTube videos have themselves had a direct effect on world events, such as Innocence of Muslims (2012) which spurred protests and related anti-American violence internationally. TED curator Chris Anderson described a phenomenon by which geographically distributed individuals in a certain field share their independently developed skills in YouTube videos, thus challenging others to improve their own skills, and spurring invention and evolution in that field. Journalist Virginia Heffernan stated in The New York Times that such videos have "surprising implications" for the dissemination of culture and even the future of classical music.
A 2017 article in The New York Times Magazine posited that YouTube had become "the new talk radio" for the far right. Almost a year before YouTube's January 2019 announcement that it would begin a "gradual change" of "reducing recommendations of borderline content and content that could misinform users in harmful ways", Zeynep Tufekci had written in The New York Times that, "(g)iven its billion or so users, YouTube may be one of the most powerful radicalizing instruments of the 21st century". Under YouTube's changes to its recommendation engine, the most recommended channel evolved from conspiracy theorist Alex Jones (2016) to Fox News (2019). According to a 2020 study, "An emerging journalistic consensus theorizes the central role played by the video 'recommendation engine,' but we believe that this is premature. Instead, we propose the 'Supply and Demand' framework for analyzing politics on YouTube." A 2022 study found that "despite widespread concerns that YouTube's algorithms send people down 'rabbit holes' with recommendations to extremist videos, little systematic evidence exists to support this conjecture", "exposure to alternative and extremist channel videos on YouTube is heavily concentrated among a small group of people with high prior levels of gender and racial resentment.", and "contrary to the 'rabbit holes' narrative, non-subscribers are rarely recommended videos from alternative and extremist channels and seldom follow such recommendations when offered."
The Legion of Extraordinary Dancers and the YouTube Symphony Orchestra selected their membership based on individual video performances. Further, the cyber-collaboration charity video "We Are the World 25 for Haiti (YouTube edition)" was formed by mixing performances of 57 globally distributed singers into a single musical work, with The Tokyo Times noting the "We Pray for You" YouTube cyber-collaboration video as an example of a trend to use crowdsourcing for charitable purposes.
The anti-bullying It Gets Better Project expanded from a single YouTube video directed to discouraged or suicidal LGBT teens, that within two months drew video responses from hundreds including U.S. President Barack Obama, Vice President Biden, White House staff, and several cabinet secretaries. Similarly, in response to fifteen-year-old Amanda Todd's video "My story: Struggling, bullying, suicide, self-harm", legislative action was undertaken almost immediately after her suicide to study the prevalence of bullying and form a national anti-bullying strategy. In May 2018, after London Metropolitan Police claimed that drill music videos glamorizing violence gave rise to gang violence, YouTube deleted 30 videos.
== Finances ==
Prior to 2020, Google did not provide detailed figures for YouTube's running costs, and YouTube's revenues in 2007 were noted as "not material" in a regulatory filing. In June 2008, a Forbes magazine article projected the 2008 revenue at $200 million, noting progress in advertising sales. In 2012, YouTube's revenue from its ads program was estimated at $3.7 billion. In 2013, it nearly doubled and estimated to hit $5.6 billion according to e-Marketer, while others estimated $4.7 billion. The vast majority of videos on YouTube are free to view and supported by advertising. In May 2013, YouTube introduced a trial scheme of 53 subscription channels with prices ranging from $0.99 to $6.99 a month. The move was seen as an attempt to compete with other providers of online subscription services such as Netflix, Amazon Prime, and Hulu.
Google first published exact revenue numbers for YouTube in February 2020 as part of Alphabet's 2019 financial report. According to Google, YouTube had made US$15.1 billion in ad revenue in 2019, in contrast to US$8.1 billion in 2017 and US$11.1 billion in 2018. YouTube's revenues made up nearly 10% of the total Alphabet revenue in 2019. These revenues accounted for approximately 20 million subscribers combined between YouTube Premium and YouTube Music subscriptions, and 2 million subscribers to YouTube TV.
YouTube had $29.2 billion ads revenue in 2022, up by $398 million from the prior year.
=== Partnership with corporations ===
YouTube entered into a marketing and advertising partnership with NBC in June 2006. In March 2007, it struck a deal with BBC for three channels with BBC content, one for news and two for entertainment. In November 2008, YouTube reached an agreement with MGM, Lions Gate Entertainment, and CBS, allowing the companies to post full-length films and television episodes on the site, accompanied by advertisements in a section for U.S. viewers called "Shows". The move was intended to create competition with websites such as Hulu, which features material from NBC, Fox, and Disney. In November 2009, YouTube launched a version of "Shows" available to UK viewers, offering around 4,000 full-length shows from more than 60 partners. In January 2010, YouTube introduced an online film rentals service, which is only available to users in the United States, Canada, and the UK as of 2010. The service offers over 6,000 films.
==== 2017 advertiser boycott ====
In March 2017, the government of the United Kingdom pulled its advertising campaigns from YouTube, after reports that its ads had appeared on videos containing extremist content. The government demanded assurances that its advertising would "be delivered safely and appropriately". The Guardian newspaper, as well as other major British and U.S. brands, similarly suspended their advertising on YouTube in response to their advertising appearing near offensive content. Google stated that it had "begun an extensive review of our advertising policies and have made a public commitment to put in place changes that give brands more control over where their ads appear". In early April 2017, the YouTube channel h3h3Productions presented evidence claiming that a Wall Street Journal article had fabricated screenshots showing major brand advertising on an offensive video containing Johnny Rebel music overlaid on a Chief Keef music video, citing that the video itself had not earned any ad revenue for the uploader. The video was retracted after it was found that the ads had been triggered by the use of copyrighted content in the video.
On April 6, 2017, YouTube announced that to "ensure revenue only flows to creators who are playing by the rules", it would change its practices to require that a channel undergo a policy compliance review, and have at least 10,000-lifetime views, before they may join the Partner Program.
=== YouTuber earnings ===
In May 2007, YouTube launched its Partner Program (YPP), a system based on AdSense which allows the uploader of the video to share the revenue produced by advertising on the site. YouTube typically takes 45 percent of the advertising revenue from videos in the Partner Program, with 55 percent going to the uploader.
There are over two million members of the YouTube Partner Program. According to TubeMogul, in 2013 a pre-roll advertisement on YouTube (one that is shown before the video starts) cost advertisers on average $7.60 per 1000 views. Usually, no more than half of the eligible videos have a pre-roll advertisement, due to a lack of interested advertisers.
YouTube's policies restrict certain forms of content from being included in videos being monetized with advertising, including videos containing violence, strong language, sexual content, "controversial or sensitive subjects and events, including subjects related to war, political conflicts, natural disasters and tragedies, even if graphic imagery is not shown" (unless the content is "usually newsworthy or comedic and the creator's intent is to inform or entertain"), and videos whose user comments contain "inappropriate" content.
In 2013, YouTube introduced an option for channels with at least a thousand subscribers to require a paid subscription in order for viewers to watch videos. In April 2017, YouTube set an eligibility requirement of 10,000 lifetime views for a paid subscription. On January 16, 2018, the eligibility requirement for monetization was changed to 4,000 hours of watch-time within the past 12 months and 1,000 subscribers. The move was seen as an attempt to ensure that videos being monetized did not lead to controversy, but was criticized for penalizing smaller YouTube channels.
YouTube Play Buttons, a part of the YouTube Creator Rewards, are a recognition by YouTube of its most popular channels. The trophies made of nickel plated copper-nickel alloy, golden plated brass, silver plated metal, ruby, and red tinted crystal glass are given to channels with at least one hundred thousand, a million, ten million, fifty million subscribers, and one hundred million subscribers, respectively.
YouTube's policies on "advertiser-friendly content" restrict what may be incorporated into videos being monetized; this includes strong violence, language, sexual content, and "controversial or sensitive subjects and events, including subjects related to war, political conflicts, natural disasters and tragedies, even if graphic imagery is not shown", unless the content is "usually newsworthy or comedic and the creator's intent is to inform or entertain". In September 2016, after introducing an enhanced notification system to inform users of these violations, YouTube's policies were criticized by prominent users, including Philip DeFranco and Vlogbrothers. DeFranco argued that not being able to earn advertising revenue on such videos was "censorship by a different name". A YouTube spokesperson stated that while the policy itself was not new, the service had "improved the notification and appeal process to ensure better communication to our creators". Boing Boing reported in 2019 that LGBT keywords resulted in demonetization.
As of November 2020 in the United States, and June 2021 worldwide, YouTube reserves the right to monetize any video on the platform, even if their uploader is not a member of the YouTube Partner Program. This will occur on channels whose content is deemed "advertiser-friendly", and all revenue will go directly to Google without any share given to the uploader.
=== Revenue to copyright holders ===
The majority of YouTube's advertising revenue goes to the publishers and video producers who hold the rights to their videos; the company retains 45% of the ad revenue. In 2010, it was reported that nearly a third of the videos with advertisements were uploaded without permission of the copyright holders. YouTube gives an option for copyright holders to locate and remove their videos or to have them continue running for revenue. In May 2013, Nintendo began enforcing its copyright ownership and claiming the advertising revenue from video creators who posted screenshots of its games. In February 2015, Nintendo agreed to share the revenue with the video creators through the Nintendo Creators Program. On March 20, 2019, Nintendo announced on Twitter that the company will end the Creators program. Operations for the program ceased on March 20, 2019.
== Censorship and bans ==
YouTube has been censored, filtered, or banned for a variety of reasons, including:
Limiting public access and exposure to content that may ignite social or political unrest.
Preventing criticism of a ruler (e.g. in North Korea), government (e.g. in China) or its actions (e.g. in Morocco), government officials (e.g. in Turkey and Libya), or religion (e.g. in Pakistan).
Morality-based laws, e.g. in Iran.
Access to specific videos is sometimes prevented due to copyright and intellectual property protection laws (e.g. in Germany), violations of hate speech, and preventing access to videos judged inappropriate for youth, which is also done by YouTube with the YouTube Kids app and with "restricted mode". Businesses, schools, government agencies, and other private institutions often block social media sites, including YouTube, due to its bandwidth limitations and the site's potential for distraction.
As of 2018, public access to YouTube is blocked in many countries, including China, North Korea, Iran, Turkmenistan, Uzbekistan, Tajikistan, Eritrea, Sudan and South Sudan. In some countries, YouTube is blocked for more limited periods of time such as during periods of unrest, the run-up to an election, or in response to upcoming political anniversaries. In cases where the entire site is banned due to one particular video, YouTube will often agree to remove or limit access to that video in order to restore service.
Reports emerged that since October 2019, comments posted with Chinese characters insulting the Chinese Communist Party (共匪 "communist bandit" or 五毛 "50 Cent Party", referring to state-sponsored commentators) were being automatically deleted within 15 seconds.
Specific incidents where YouTube has been blocked include:
Thailand blocked access in April 2007 over a video said to be insulting the Thai king.
Morocco blocked access in May 2007, possibly as a result of videos critical of Morocco's occupation of Western Sahara. YouTube became accessible again on May 30, 2007, after Maroc Telecom unofficially announced that the denied access to the website was a mere "technical glitch".
Turkey blocked access between 2008 and 2010 after controversy over videos deemed insulting to Mustafa Kemal Atatürk. In November 2010, a video of the Turkish politician Deniz Baykal caused the site to be blocked again briefly, and the site was threatened with a new shutdown if it did not remove the video. During the two and a half-year block of YouTube, the video-sharing website remained the eighth-most-accessed site in Turkey. In 2014, Turkey blocked the access for the second time, after "a high-level intelligence leak."
Pakistan blocked access on February 23, 2008, because of "offensive material" towards the Islamic faith, including display of the Danish cartoons of Muhammad. This led to a near global blackout of the YouTube site for around two hours, as the Pakistani block was inadvertently transferred to other countries. On February 26, 2008, the ban was lifted after the website had removed the objectionable content from its servers at the request of the government. Many Pakistanis circumvented the three-day block by using virtual private network software. In May 2010, following the Everybody Draw Mohammed Day, Pakistan again blocked access to YouTube, citing "growing sacrilegious content". The ban was lifted on May 27, 2010, after the website removed the objectionable content from its servers at the request of the government. However, individual videos deemed offensive to Muslims posted on YouTube will continue to be blocked. Pakistan again placed a ban on YouTube in September 2012, after the site refused to remove the film Innocence of Muslims. The ban was lifted in January 2016 after YouTube launched a Pakistan-specific version.
Libya blocked access on January 24, 2010, because of videos that featured demonstrations in the city of Benghazi by families of detainees who were killed in Abu Salim prison in 1996, and videos of family members of Libyan leader Muammar Gaddafi at parties. The blocking was criticized by Human Rights Watch. In November 2011, after the Libyan Civil War, YouTube was once again allowed in Libya.
Afghanistan, Bangladesh, Pakistan, and Sudan blocked access in September 2012 following controversy over a 14-minute trailer for the film Innocence of Muslims which had been posted on the site. A court in the southern Russian Republic of Chechnya ruled that Innocence of Muslims should be banned. In Libya and Egypt, it was blamed for violent protests. YouTube stated: "This video—which is widely available on the Web—is clearly within our guidelines and so will stay on YouTube. However, given the very difficult situation in Libya and Egypt we have temporarily restricted access in both countries."
Following the Russian invasion of Ukraine in February 2022, YouTube announced on March 1 the immediate removal of RT (and other Russian-government funded outlets) from its platform in Europe. The removal was soon expanded globally.
== See also ==
iFilm
Google Video
Metacafe
Revver
vMix
blip.tv
Videosift
== Further reading ==
== Notes ==
== References ==
== External links ==
Official website | YouTube is an American online video sharing platform owned by Google. Accessible worldwide, YouTube was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim, three former employees of PayPal. Headquartered in San Bruno, California, United States, it is the second most visited website in the world, after Google Search. YouTube has more than 2.5 billion monthly users, who collectively watch more than one billion hours of videos every day. As of May 2019, videos were being uploaded to the platform at a rate of more than 500 hours of content per minute, and as of 2021, there were approximately 14 billion videos in total.
In October 2006, YouTube was purchased by Google for $1.65 billion (equivalent to $2.31 billion in 2023). Google expanded YouTube's business model of generating revenue from advertisements alone, to offering paid content such as movies and exclusive content produced by and for YouTube. It also offers YouTube Premium, a paid subscription option for watching content without ads. YouTube incorporated Google's AdSense program, generating more revenue for both YouTube and approved content creators. In 2022, YouTube's annual advertising revenue increased to $29.2 billion, more than $9 billion higher than in 2020.
Since its purchase by Google, YouTube has expanded beyond the core website into mobile apps, network television, and the ability to link with other platforms. Video categories on YouTube include music videos, video clips, news, short and feature films, songs, documentaries, movie trailers, teasers and TV spots, live streams, vlogs, and more. Most content is generated by individuals, including collaborations between "YouTubers" and corporate sponsors. Established media, news, and entertainment corporations have also created and expanded their visibility to YouTube channels in order to reach greater audiences.
YouTube has had unprecedented social impact, influencing popular culture, internet trends, and creating multimillionaire celebrities. Despite its growth and success, the platform is sometimes criticized for allegedly facilitating the spread of misinformation, the sharing of copyrighted content, routinely violating its users' privacy, enabling censorship, endangering child safety and wellbeing, and for its inconsistent or incorrect implementation of platform guidelines. | 15 |
324 | dbms | Database (wikipedia) | In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an application associated with the database.
Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases spans formal techniques and practical considerations, including data modeling, efficient data representation and storage, query languages, security and privacy of sensitive data, and distributed computing issues, including supporting concurrent access and fault tolerance.
Computer scientists may classify database management systems according to the database models that they support. Relational databases became dominant in the 1980s. These model data as rows and columns in a series of tables, and the vast majority use SQL for writing and querying data. In the 2000s, non-relational databases became popular, collectively referred to as NoSQL, because they use different query languages.
== Terminology and overview ==
Formally, a "database" refers to a set of related data accessed through the use of a "database management system" (DBMS), which is an integrated set of computer software that allows users to interact with one or more databases and provides access to all of the data contained in the database (although restrictions may exist that limit access to particular data). The DBMS provides various functions that allow entry, storage and retrieval of large quantities of information and provides ways to manage how that information is organized.
Because of the close relationship between them, the term "database" is often used casually to refer to both a database and the DBMS used to manipulate it.
Outside the world of professional information technology, the term database is often used to refer to any collection of related data (such as a spreadsheet or a card index) as size and usage requirements typically necessitate use of a database management system.
Existing DBMSs provide various functions that allow management of a database and its data which can be classified into four main functional groups:
Data definition – Creation, modification and removal of definitions that detail how the data is to be organized.
Update – Insertion, modification, and deletion of the data itself.
Retrieval – Selecting data according to specified criteria (e.g., a query, a position in a hierarchy, or a position in relation to other data) and providing that data either directly to the user, or making it available for further processing by the database itself or by other applications. The retrieved data may be made available in a more or less direct form without modification, as it is stored in the database, or in a new form obtained by altering it or combining it with existing data from the database.
Administration – Registering and monitoring users, enforcing data security, monitoring performance, maintaining data integrity, dealing with concurrency control, and recovering information that has been corrupted by some event such as an unexpected system failure.
Both a database and its DBMS conform to the principles of a particular database model. "Database system" refers collectively to the database model, database management system, and database.
Physically, database servers are dedicated computers that hold the actual databases and run only the DBMS and related software. Database servers are usually multiprocessor computers, with generous memory and RAID disk arrays used for stable storage. Hardware database accelerators, connected to one or more servers via a high-speed channel, are also used in large-volume transaction processing environments. DBMSs are found at the heart of most database applications. DBMSs may be built around a custom multitasking kernel with built-in networking support, but modern DBMSs typically rely on a standard operating system to provide these functions.
Since DBMSs comprise a significant market, computer and storage vendors often take into account DBMS requirements in their own development plans.
Databases and DBMSs can be categorized according to the database model(s) that they support (such as relational or XML), the type(s) of computer they run on (from a server cluster to a mobile phone), the query language(s) used to access the database (such as SQL or XQuery), and their internal engineering, which affects performance, scalability, resilience, and security.
== History ==
The sizes, capabilities, and performance of databases and their respective DBMSs have grown in orders of magnitude. These performance increases were enabled by the technology progress in the areas of processors, computer memory, computer storage, and computer networks. The concept of a database was made possible by the emergence of direct access storage media such as magnetic disks, which became widely available in the mid-1960s; earlier systems relied on sequential storage of data on magnetic tape. The subsequent development of database technology can be divided into three eras based on data model or structure: navigational, SQL/relational, and post-relational.
The two main early navigational data models were the hierarchical model and the CODASYL model (network model). These were characterized by the use of pointers (often physical disk addresses) to follow relationships from one record to another.
The relational model, first proposed in 1970 by Edgar F. Codd, departed from this tradition by insisting that applications should search for data by content, rather than by following links. The relational model employs sets of ledger-style tables, each used for a different type of entity. Only in the mid-1980s did computing hardware become powerful enough to allow the wide deployment of relational systems (DBMSs plus applications). By the early 1990s, however, relational systems dominated in all large-scale data processing applications, and as of 2018 they remain dominant: IBM Db2, Oracle, MySQL, and Microsoft SQL Server are the most searched DBMS. The dominant database language, standardized SQL for the relational model, has influenced database languages for other data models.
Object databases were developed in the 1980s to overcome the inconvenience of object–relational impedance mismatch, which led to the coining of the term "post-relational" and also the development of hybrid object–relational databases.
The next generation of post-relational databases in the late 2000s became known as NoSQL databases, introducing fast key–value stores and document-oriented databases. A competing "next generation" known as NewSQL databases attempted new implementations that retained the relational/SQL model while aiming to match the high performance of NoSQL compared to commercially available relational DBMSs.
=== 1960s, navigational DBMS ===
The introduction of the term database coincided with the availability of direct-access storage (disks and drums) from the mid-1960s onwards. The term represented a contrast with the tape-based systems of the past, allowing shared interactive use rather than daily batch processing. The Oxford English Dictionary cites a 1962 report by the System Development Corporation of California as the first to use the term "data-base" in a specific technical sense.
As computers grew in speed and capability, a number of general-purpose database systems emerged; by the mid-1960s a number of such systems had come into commercial use. Interest in a standard began to grow, and Charles Bachman, author of one such product, the Integrated Data Store (IDS), founded the Database Task Group within CODASYL, the group responsible for the creation and standardization of COBOL. In 1971, the Database Task Group delivered their standard, which generally became known as the CODASYL approach, and soon a number of commercial products based on this approach entered the market.
The CODASYL approach offered applications the ability to navigate around a linked data set which was formed into a large network. Applications could find records by one of three methods:
Use of a primary key (known as a CALC key, typically implemented by hashing)
Navigating relationships (called sets) from one record to another
Scanning all the records in a sequential order
Later systems added B-trees to provide alternate access paths. Many CODASYL databases also added a declarative query language for end users (as distinct from the navigational API). However, CODASYL databases were complex and required significant training and effort to produce useful applications.
IBM also had its own DBMS in 1966, known as Information Management System (IMS). IMS was a development of software written for the Apollo program on the System/360. IMS was generally similar in concept to CODASYL, but used a strict hierarchy for its model of data navigation instead of CODASYL's network model. Both concepts later became known as navigational databases due to the way data was accessed: the term was popularized by Bachman's 1973 Turing Award presentation The Programmer as Navigator. IMS is classified by IBM as a hierarchical database. IDMS and Cincom Systems' TOTAL databases are classified as network databases. IMS remains in use as of 2014.
=== 1970s, relational DBMS ===
Edgar F. Codd worked at IBM in San Jose, California, in one of their offshoot offices that were primarily involved in the development of hard disk systems. He was unhappy with the navigational model of the CODASYL approach, notably the lack of a "search" facility. In 1970, he wrote a number of papers that outlined a new approach to database construction that eventually culminated in the groundbreaking A Relational Model of Data for Large Shared Data Banks.
In this paper, he described a new system for storing and working with large databases. Instead of records being stored in some sort of linked list of free-form records as in CODASYL, Codd's idea was to organize the data as a number of "tables", each table being used for a different type of entity. Each table would contain a fixed number of columns containing the attributes of the entity. One or more columns of each table were designated as a primary key by which the rows of the table could be uniquely identified; cross-references between tables always used these primary keys, rather than disk addresses, and queries would join tables based on these key relationships, using a set of operations based on the mathematical system of relational calculus (from which the model takes its name). Splitting the data into a set of normalized tables (or relations) aimed to ensure that each "fact" was only stored once, thus simplifying update operations. Virtual tables called views could present the data in different ways for different users, but views could not be directly updated.
Codd used mathematical terms to define the model: relations, tuples, and domains rather than tables, rows, and columns. The terminology that is now familiar came from early implementations. Codd would later criticize the tendency for practical implementations to depart from the mathematical foundations on which the model was based.
The use of primary keys (user-oriented identifiers) to represent cross-table relationships, rather than disk addresses, had two primary motivations. From an engineering perspective, it enabled tables to be relocated and resized without expensive database reorganization. But Codd was more interested in the difference in semantics: the use of explicit identifiers made it easier to define update operations with clean mathematical definitions, and it also enabled query operations to be defined in terms of the established discipline of first-order predicate calculus; because these operations have clean mathematical properties, it becomes possible to rewrite queries in provably correct ways, which is the basis of query optimization. There is no loss of expressiveness compared with the hierarchic or network models, though the connections between tables are no longer so explicit.
In the hierarchic and network models, records were allowed to have a complex internal structure. For example, the salary history of an employee might be represented as a "repeating group" within the employee record. In the relational model, the process of normalization led to such internal structures being replaced by data held in multiple tables, connected only by logical keys.
For instance, a common use of a database system is to track information about users, their name, login information, various addresses and phone numbers. In the navigational approach, all of this data would be placed in a single variable-length record. In the relational approach, the data would be normalized into a user table, an address table and a phone number table (for instance). Records would be created in these optional tables only if the address or phone numbers were actually provided.
As well as identifying rows/records using logical identifiers rather than disk addresses, Codd changed the way in which applications assembled data from multiple records. Rather than requiring applications to gather data one record at a time by navigating the links, they would use a declarative query language that expressed what data was required, rather than the access path by which it should be found. Finding an efficient access path to the data became the responsibility of the database management system, rather than the application programmer. This process, called query optimization, depended on the fact that queries were expressed in terms of mathematical logic.
Codd's paper was picked up by two people at Berkeley, Eugene Wong and Michael Stonebraker. They started a project known as INGRES using funding that had already been allocated for a geographical database project and student programmers to produce code. Beginning in 1973, INGRES delivered its first test products which were generally ready for widespread use in 1979. INGRES was similar to System R in a number of ways, including the use of a "language" for data access, known as QUEL. Over time, INGRES moved to the emerging SQL standard.
IBM itself did one test implementation of the relational model, PRTV, and a production one, Business System 12, both now discontinued. Honeywell wrote MRDS for Multics, and now there are two new implementations: Alphora Dataphor and Rel. Most other DBMS implementations usually called relational are actually SQL DBMSs.
In 1970, the University of Michigan began development of the MICRO Information Management System based on D.L. Childs' Set-Theoretic Data model. MICRO was used to manage very large data sets by the US Department of Labor, the U.S. Environmental Protection Agency, and researchers from the University of Alberta, the University of Michigan, and Wayne State University. It ran on IBM mainframe computers using the Michigan Terminal System. The system remained in production until 1998.
=== Integrated approach ===
In the 1970s and 1980s, attempts were made to build database systems with integrated hardware and software. The underlying philosophy was that such integration would provide higher performance at a lower cost. Examples were IBM System/38, the early offering of Teradata, and the Britton Lee, Inc. database machine.
Another approach to hardware support for database management was ICL's CAFS accelerator, a hardware disk controller with programmable search capabilities. In the long term, these efforts were generally unsuccessful because specialized database machines could not keep pace with the rapid development and progress of general-purpose computers. Thus most database systems nowadays are software systems running on general-purpose hardware, using general-purpose computer data storage. However, this idea is still pursued in certain applications by some companies like Netezza and Oracle (Exadata).
=== Late 1970s, SQL DBMS ===
IBM started working on a prototype system loosely based on Codd's concepts as System R in the early 1970s. The first version was ready in 1974/5, and work then started on multi-table systems in which the data could be split so that all of the data for a record (some of which is optional) did not have to be stored in a single large "chunk". Subsequent multi-user versions were tested by customers in 1978 and 1979, by which time a standardized query language – SQL – had been added. Codd's ideas were establishing themselves as both workable and superior to CODASYL, pushing IBM to develop a true production version of System R, known as SQL/DS, and, later, Database 2 (IBM Db2).
Larry Ellison's Oracle Database (or more simply, Oracle) started from a different chain, based on IBM's papers on System R. Though Oracle V1 implementations were completed in 1978, it was not until Oracle Version 2 when Ellison beat IBM to market in 1979.
Stonebraker went on to apply the lessons from INGRES to develop a new database, Postgres, which is now known as PostgreSQL. PostgreSQL is often used for global mission-critical applications (the .org and .info domain name registries use it as their primary data store, as do many large companies and financial institutions).
In Sweden, Codd's paper was also read and Mimer SQL was developed in the mid-1970s at Uppsala University. In 1984, this project was consolidated into an independent enterprise.
Another data model, the entity–relationship model, emerged in 1976 and gained popularity for database design as it emphasized a more familiar description than the earlier relational model. Later on, entity–relationship constructs were retrofitted as a data modeling construct for the relational model, and the difference between the two has become irrelevant.
=== 1980s, on the desktop ===
The 1980s ushered in the age of desktop computing. The new computers empowered their users with spreadsheets like Lotus 1-2-3 and database software like dBASE. The dBASE product was lightweight and easy for any computer user to understand out of the box. C. Wayne Ratliff, the creator of dBASE, stated: "dBASE was different from programs like BASIC, C, FORTRAN, and COBOL in that a lot of the dirty work had already been done. The data manipulation is done by dBASE instead of by the user, so the user can concentrate on what he is doing, rather than having to mess with the dirty details of opening, reading, and closing files, and managing space allocation." dBASE was one of the top selling software titles in the 1980s and early 1990s.
=== 1990s, object-oriented ===
The 1990s, along with a rise in object-oriented programming, saw a growth in how data in various databases were handled. Programmers and designers began to treat the data in their databases as objects. That is to say that if a person's data were in a database, that person's attributes, such as their address, phone number, and age, were now considered to belong to that person instead of being extraneous data. This allows for relations between data to be related to objects and their attributes and not to individual fields. The term "object–relational impedance mismatch" described the inconvenience of translating between programmed objects and database tables. Object databases and object–relational databases attempt to solve this problem by providing an object-oriented language (sometimes as extensions to SQL) that programmers can use as alternative to purely relational SQL. On the programming side, libraries known as object–relational mappings (ORMs) attempt to solve the same problem.
=== 2000s, NoSQL and NewSQL ===
XML databases are a type of structured document-oriented database that allows querying based on XML document attributes. XML databases are mostly used in applications where the data is conveniently viewed as a collection of documents, with a structure that can vary from the very flexible to the highly rigid: examples include scientific articles, patents, tax filings, and personnel records.
NoSQL databases are often very fast, do not require fixed table schemas, avoid join operations by storing denormalized data, and are designed to scale horizontally.
In recent years, there has been a strong demand for massively distributed databases with high partition tolerance, but according to the CAP theorem, it is impossible for a distributed system to simultaneously provide consistency, availability, and partition tolerance guarantees. A distributed system can satisfy any two of these guarantees at the same time, but not all three. For that reason, many NoSQL databases are using what is called eventual consistency to provide both availability and partition tolerance guarantees with a reduced level of data consistency.
NewSQL is a class of modern relational databases that aims to provide the same scalable performance of NoSQL systems for online transaction processing (read-write) workloads while still using SQL and maintaining the ACID guarantees of a traditional database system.
== Use cases ==
Databases are used to support internal operations of organizations and to underpin online interactions with customers and suppliers (see Enterprise software).
Databases are used to hold administrative information and more specialized data, such as engineering data or economic models. Examples include computerized library systems, flight reservation systems, computerized parts inventory systems, and many content management systems that store websites as collections of webpages in a database.
== Classification ==
One way to classify databases involves the type of their contents, for example: bibliographic, document-text, statistical, or multimedia objects. Another way is by their application area, for example: accounting, music compositions, movies, banking, manufacturing, or insurance. A third way is by some technical aspect, such as the database structure or interface type. This section lists a few of the adjectives used to characterize different kinds of databases.
An in-memory database is a database that primarily resides in main memory, but is typically backed-up by non-volatile computer data storage. Main memory databases are faster than disk databases, and so are often used where response time is critical, such as in telecommunications network equipment.
An active database includes an event-driven architecture which can respond to conditions both inside and outside the database. Possible uses include security monitoring, alerting, statistics gathering and authorization. Many databases provide active database features in the form of database triggers.
A cloud database relies on cloud technology. Both the database and most of its DBMS reside remotely, "in the cloud", while its applications are both developed by programmers and later maintained and used by end-users through a web browser and Open APIs.
Data warehouses archive data from operational databases and often from external sources such as market research firms. The warehouse becomes the central source of data for use by managers and other end-users who may not have access to operational data. For example, sales data might be aggregated to weekly totals and converted from internal product codes to use UPCs so that they can be compared with ACNielsen data. Some basic and essential components of data warehousing include extracting, analyzing, and mining data, transforming, loading, and managing data so as to make them available for further use.
A deductive database combines logic programming with a relational database.
A distributed database is one in which both the data and the DBMS span multiple computers.
A document-oriented database is designed for storing, retrieving, and managing document-oriented, or semi structured, information. Document-oriented databases are one of the main categories of NoSQL databases.
An embedded database system is a DBMS which is tightly integrated with an application software that requires access to stored data in such a way that the DBMS is hidden from the application's end-users and requires little or no ongoing maintenance.
End-user databases consist of data developed by individual end-users. Examples of these are collections of documents, spreadsheets, presentations, multimedia, and other files. Several products exist to support such databases.
A federated database system comprises several distinct databases, each with its own DBMS. It is handled as a single database by a federated database management system (FDBMS), which transparently integrates multiple autonomous DBMSs, possibly of different types (in which case it would also be a heterogeneous database system), and provides them with an integrated conceptual view.
Sometimes the term multi-database is used as a synonym for federated database, though it may refer to a less integrated (e.g., without an FDBMS and a managed integrated schema) group of databases that cooperate in a single application. In this case, typically middleware is used for distribution, which typically includes an atomic commit protocol (ACP), e.g., the two-phase commit protocol, to allow distributed (global) transactions across the participating databases.
A graph database is a kind of NoSQL database that uses graph structures with nodes, edges, and properties to represent and store information. General graph databases that can store any graph are distinct from specialized graph databases such as triplestores and network databases.
An array DBMS is a kind of NoSQL DBMS that allows modeling, storage, and retrieval of (usually large) multi-dimensional arrays such as satellite images and climate simulation output.
In a hypertext or hypermedia database, any word or a piece of text representing an object, e.g., another piece of text, an article, a picture, or a film, can be hyperlinked to that object. Hypertext databases are particularly useful for organizing large amounts of disparate information. For example, they are useful for organizing online encyclopedias, where users can conveniently jump around the text. The World Wide Web is thus a large distributed hypertext database.
A knowledge base (abbreviated KB, kb or Δ) is a special kind of database for knowledge management, providing the means for the computerized collection, organization, and retrieval of knowledge. Also a collection of data representing problems with their solutions and related experiences.
A mobile database can be carried on or synchronized from a mobile computing device.
Operational databases store detailed data about the operations of an organization. They typically process relatively high volumes of updates using transactions. Examples include customer databases that record contact, credit, and demographic information about a business's customers, personnel databases that hold information such as salary, benefits, skills data about employees, enterprise resource planning systems that record details about product components, parts inventory, and financial databases that keep track of the organization's money, accounting and financial dealings.
A parallel database seeks to improve performance through parallelization for tasks such as loading data, building indexes and evaluating queries.
The major parallel DBMS architectures which are induced by the underlying hardware architecture are:
Shared memory architecture, where multiple processors share the main memory space, as well as other data storage.
Shared disk architecture, where each processing unit (typically consisting of multiple processors) has its own main memory, but all units share the other storage.
Shared-nothing architecture, where each processing unit has its own main memory and other storage.
Probabilistic databases employ fuzzy logic to draw inferences from imprecise data.
Real-time databases process transactions fast enough for the result to come back and be acted on right away.
A spatial database can store the data with multidimensional features. The queries on such data include location-based queries, like "Where is the closest hotel in my area?".
A temporal database has built-in time aspects, for example a temporal data model and a temporal version of SQL. More specifically the temporal aspects usually include valid-time and transaction-time.
A terminology-oriented database builds upon an object-oriented database, often customized for a specific field.
An unstructured data database is intended to store in a manageable and protected way diverse objects that do not fit naturally and conveniently in common databases. It may include email messages, documents, journals, multimedia objects, etc. The name may be misleading since some objects can be highly structured. However, the entire possible object collection does not fit into a predefined structured framework. Most established DBMSs now support unstructured data in various ways, and new dedicated DBMSs are emerging.
== Database management system ==
Connolly and Begg define database management system (DBMS) as a "software system that enables users to define, create, maintain and control access to the database." Examples of DBMS's include MySQL, MariaDB, PostgreSQL, Microsoft SQL Server, Oracle Database, and Microsoft Access.
The DBMS acronym is sometimes extended to indicate the underlying database model, with RDBMS for the relational, OODBMS for the object (oriented) and ORDBMS for the object–relational model. Other extensions can indicate some other characteristics, such as DDBMS for a distributed database management systems.
The functionality provided by a DBMS can vary enormously. The core functionality is the storage, retrieval and update of data. Codd proposed the following functions and services a fully-fledged general purpose DBMS should provide:
Data storage, retrieval and update
User accessible catalog or data dictionary describing the metadata
Support for transactions and concurrency
Facilities for recovering the database should it become damaged
Support for authorization of access and update of data
Access support from remote locations
Enforcing constraints to ensure data in the database abides by certain rules
It is also generally to be expected the DBMS will provide a set of utilities for such purposes as may be necessary to administer the database effectively, including import, export, monitoring, defragmentation and analysis utilities. The core part of the DBMS interacting between the database and the application interface sometimes referred to as the database engine.
Often DBMSs will have configuration parameters that can be statically and dynamically tuned, for example the maximum amount of main memory on a server the database can use. The trend is to minimize the amount of manual configuration, and for cases such as embedded databases the need to target zero-administration is paramount.
The large major enterprise DBMSs have tended to increase in size and functionality and have involved up to thousands of human years of development effort throughout their lifetime.
Early multi-user DBMS typically only allowed for the application to reside on the same computer with access via terminals or terminal emulation software. The client–server architecture was a development where the application resided on a client desktop and the database on a server allowing the processing to be distributed. This evolved into a multitier architecture incorporating application servers and web servers with the end user interface via a web browser with the database only directly connected to the adjacent tier.
A general-purpose DBMS will provide public application programming interfaces (API) and optionally a processor for database languages such as SQL to allow applications to be written to interact with and manipulate the database. A special purpose DBMS may use a private API and be specifically customized and linked to a single application. For example, an email system performs many of the functions of a general-purpose DBMS such as message insertion, message deletion, attachment handling, blocklist lookup, associating messages an email address and so forth however these functions are limited to what is required to handle email.
== Application ==
External interaction with the database will be via an application program that interfaces with the DBMS. This can range from a database tool that allows users to execute SQL queries textually or graphically, to a website that happens to use a database to store and search information.
=== Application program interface ===
A programmer will code interactions to the database (sometimes referred to as a datasource) via an application program interface (API) or via a database language. The particular API or language chosen will need to be supported by DBMS, possibly indirectly via a preprocessor or a bridging API. Some API's aim to be database independent, ODBC being a commonly known example. Other common API's include JDBC and ADO.NET.
== Database languages ==
Database languages are special-purpose languages, which allow one or more of the following tasks, sometimes distinguished as sublanguages:
Data control language (DCL) – controls access to data;
Data definition language (DDL) – defines data types such as creating, altering, or dropping tables and the relationships among them;
Data manipulation language (DML) – performs tasks such as inserting, updating, or deleting data occurrences;
Data query language (DQL) – allows searching for information and computing derived information.
Database languages are specific to a particular data model. Notable examples include:
SQL combines the roles of data definition, data manipulation, and query in a single language. It was one of the first commercial languages for the relational model, although it departs in some respects from the relational model as described by Codd (for example, the rows and columns of a table can be ordered). SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987. The standards have been regularly enhanced since and are supported (with varying degrees of conformance) by all mainstream commercial relational DBMSs.
OQL is an object model language standard (from the Object Data Management Group). It has influenced the design of some of the newer query languages like JDOQL and EJB QL.
XQuery is a standard XML query language implemented by XML database systems such as MarkLogic and eXist, by relational databases with XML capability such as Oracle and Db2, and also by in-memory XML processors such as Saxon.
SQL/XML combines XQuery with SQL.
A database language may also incorporate features like:
DBMS-specific configuration and storage engine management
Computations to modify query results, like counting, summing, averaging, sorting, grouping, and cross-referencing
Constraint enforcement (e.g. in an automotive database, only allowing one engine type per car)
Application programming interface version of the query language, for programmer convenience
== Storage ==
Database storage is the container of the physical materialization of a database. It comprises the internal (physical) level in the database architecture. It also contains all the information needed (e.g., metadata, "data about the data", and internal data structures) to reconstruct the conceptual level and external level from the internal level when needed. Databases as digital objects contain three layers of information which must be stored: the data, the structure, and the semantics. Proper storage of all three layers is needed for future preservation and longevity of the database. Putting data into permanent storage is generally the responsibility of the database engine a.k.a. "storage engine". Though typically accessed by a DBMS through the underlying operating system (and often using the operating systems' file systems as intermediates for storage layout), storage properties and configuration settings are extremely important for the efficient operation of the DBMS, and thus are closely maintained by database administrators. A DBMS, while in operation, always has its database residing in several types of storage (e.g., memory and external storage). The database data and the additional needed information, possibly in very large amounts, are coded into bits. Data typically reside in the storage in structures that look completely different from the way the data look at the conceptual and external levels, but in ways that attempt to optimize (the best possible) these levels' reconstruction when needed by users and programs, as well as for computing additional types of needed information from the data (e.g., when querying the database).
Some DBMSs support specifying which character encoding was used to store data, so multiple encodings can be used in the same database.
Various low-level database storage structures are used by the storage engine to serialize the data model so it can be written to the medium of choice. Techniques such as indexing may be used to improve performance. Conventional storage is row-oriented, but there are also column-oriented and correlation databases.
=== Materialized views ===
Often storage redundancy is employed to increase performance. A common example is storing materialized views, which consist of frequently needed external views or query results. Storing such views saves the expensive computing them each time they are needed. The downsides of materialized views are the overhead incurred when updating them to keep them synchronized with their original updated database data, and the cost of storage redundancy.
=== Replication ===
Occasionally a database employs storage redundancy by database objects replication (with one or more copies) to increase data availability (both to improve performance of simultaneous multiple end-user accesses to the same database object, and to provide resiliency in a case of partial failure of a distributed database). Updates of a replicated object need to be synchronized across the object copies. In many cases, the entire database is replicated.
=== Virtualization ===
With data virtualization, the data used remains in its original locations and real-time access is established to allow analytics across multiple sources. This can aid in resolving some technical difficulties such as compatibility problems when combining data from various platforms, lowering the risk of error caused by faulty data, and guaranteeing that the newest data is used. Furthermore, avoiding the creation of a new database containing personal information can make it easier to comply with privacy regulations. However, with data virtualization, the connection to all necessary data sources must be operational as there is no local copy of the data, which is one of the main drawbacks of the approach.
== Security ==
Database security deals with all various aspects of protecting the database content, its owners, and its users. It ranges from protection from intentional unauthorized database uses to unintentional database accesses by unauthorized entities (e.g., a person or a computer program).
Database access control deals with controlling who (a person or a certain computer program) are allowed to access what information in the database. The information may comprise specific database objects (e.g., record types, specific records, data structures), certain computations over certain objects (e.g., query types, or specific queries), or using specific access paths to the former (e.g., using specific indexes or other data structures to access information). Database access controls are set by special authorized (by the database owner) personnel that uses dedicated protected security DBMS interfaces.
This may be managed directly on an individual basis, or by the assignment of individuals and privileges to groups, or (in the most elaborate models) through the assignment of individuals and groups to roles which are then granted entitlements. Data security prevents unauthorized users from viewing or updating the database. Using passwords, users are allowed access to the entire database or subsets of it called "subschemas". For example, an employee database can contain all the data about an individual employee, but one group of users may be authorized to view only payroll data, while others are allowed access to only work history and medical data. If the DBMS provides a way to interactively enter and update the database, as well as interrogate it, this capability allows for managing personal databases.
Data security in general deals with protecting specific chunks of data, both physically (i.e., from corruption, or destruction, or removal; e.g., see physical security), or the interpretation of them, or parts of them to meaningful information (e.g., by looking at the strings of bits that they comprise, concluding specific valid credit-card numbers; e.g., see data encryption).
Change and access logging records who accessed which attributes, what was changed, and when it was changed. Logging services allow for a forensic database audit later by keeping a record of access occurrences and changes. Sometimes application-level code is used to record changes rather than leaving this in the database. Monitoring can be set up to attempt to detect security breaches. Therefore, organizations must take database security seriously because of the many benefits it provides. Organizations will be safeguarded from security breaches and hacking activities like firewall intrusion, virus spread, and ransom ware. This helps in protecting the company's essential information, which cannot be shared with outsiders at any cause.
== Transactions and concurrency ==
Database transactions can be used to introduce some level of fault tolerance and data integrity after recovery from a crash. A database transaction is a unit of work, typically encapsulating a number of operations over a database (e.g., reading a database object, writing, acquiring or releasing a lock, etc.), an abstraction supported in database and also other systems. Each transaction has well defined boundaries in terms of which program/code executions are included in that transaction (determined by the transaction's programmer via special transaction commands).
The acronym ACID describes some ideal properties of a database transaction: atomicity, consistency, isolation, and durability.
== Migration ==
A database built with one DBMS is not portable to another DBMS (i.e., the other DBMS cannot run it). However, in some situations, it is desirable to migrate a database from one DBMS to another. The reasons are primarily economical (different DBMSs may have different total costs of ownership or TCOs), functional, and operational (different DBMSs may have different capabilities). The migration involves the database's transformation from one DBMS type to another. The transformation should maintain (if possible) the database related application (i.e., all related application programs) intact. Thus, the database's conceptual and external architectural levels should be maintained in the transformation. It may be desired that also some aspects of the architecture internal level are maintained. A complex or large database migration may be a complicated and costly (one-time) project by itself, which should be factored into the decision to migrate. This is in spite of the fact that tools may exist to help migration between specific DBMSs. Typically, a DBMS vendor provides tools to help import databases from other popular DBMSs.
== Building, maintaining, and tuning ==
After designing a database for an application, the next stage is building the database. Typically, an appropriate general-purpose DBMS can be selected to be used for this purpose. A DBMS provides the needed user interfaces to be used by database administrators to define the needed application's data structures within the DBMS's respective data model. Other user interfaces are used to select needed DBMS parameters (like security related, storage allocation parameters, etc.).
When the database is ready (all its data structures and other needed components are defined), it is typically populated with initial application's data (database initialization, which is typically a distinct project; in many cases using specialized DBMS interfaces that support bulk insertion) before making it operational. In some cases, the database becomes operational while empty of application data, and data are accumulated during its operation.
After the database is created, initialized and populated it needs to be maintained. Various database parameters may need changing and the database may need to be tuned (tuning) for better performance; application's data structures may be changed or added, new related application programs may be written to add to the application's functionality, etc.
== Backup and restore ==
Sometimes it is desired to bring a database back to a previous state (for many reasons, e.g., cases when the database is found corrupted due to a software error, or if it has been updated with erroneous data). To achieve this, a backup operation is done occasionally or continuously, where each desired database state (i.e., the values of its data and their embedding in database's data structures) is kept within dedicated backup files (many techniques exist to do this effectively). When it is decided by a database administrator to bring the database back to this state (e.g., by specifying this state by a desired point in time when the database was in this state), these files are used to restore that state.
== Static analysis ==
Static analysis techniques for software verification can be applied also in the scenario of query languages. In particular, the *Abstract interpretation framework has been extended to the field of query languages for relational databases as a way to support sound approximation techniques. The semantics of query languages can be tuned according to suitable abstractions of the concrete domain of data. The abstraction of relational database systems has many interesting applications, in particular, for security purposes, such as fine-grained access control, watermarking, etc.
== Miscellaneous features ==
Other DBMS features might include:
Database logs – This helps in keeping a history of the executed functions.
Graphics component for producing graphs and charts, especially in a data warehouse system.
Query optimizer – Performs query optimization on every query to choose an efficient query plan (a partial order (tree) of operations) to be executed to compute the query result. May be specific to a particular storage engine.
Tools or hooks for database design, application programming, application program maintenance, database performance analysis and monitoring, database configuration monitoring, DBMS hardware configuration (a DBMS and related database may span computers, networks, and storage units) and related database mapping (especially for a distributed DBMS), storage allocation and database layout monitoring, storage migration, etc.
Increasingly, there are calls for a single system that incorporates all of these core functionalities into the same build, test, and deployment framework for database management and source control. Borrowing from other developments in the software industry, some market such offerings as "DevOps for database".
== Design and modeling ==
The first task of a database designer is to produce a conceptual data model that reflects the structure of the information to be held in the database. A common approach to this is to develop an entity–relationship model, often with the aid of drawing tools. Another popular approach is the Unified Modeling Language. A successful data model will accurately reflect the possible state of the external world being modeled: for example, if people can have more than one phone number, it will allow this information to be captured. Designing a good conceptual data model requires a good understanding of the application domain; it typically involves asking deep questions about the things of interest to an organization, like "can a customer also be a supplier?", or "if a product is sold with two different forms of packaging, are those the same product or different products?", or "if a plane flies from New York to Dubai via Frankfurt, is that one flight or two (or maybe even three)?". The answers to these questions establish definitions of the terminology used for entities (customers, products, flights, flight segments) and their relationships and attributes.
Producing the conceptual data model sometimes involves input from business processes, or the analysis of workflow in the organization. This can help to establish what information is needed in the database, and what can be left out. For example, it can help when deciding whether the database needs to hold historic data as well as current data.
Having produced a conceptual data model that users are happy with, the next stage is to translate this into a schema that implements the relevant data structures within the database. This process is often called logical database design, and the output is a logical data model expressed in the form of a schema. Whereas the conceptual data model is (in theory at least) independent of the choice of database technology, the logical data model will be expressed in terms of a particular database model supported by the chosen DBMS. (The terms data model and database model are often used interchangeably, but in this article we use data model for the design of a specific database, and database model for the modeling notation used to express that design).
The most popular database model for general-purpose databases is the relational model, or more precisely, the relational model as represented by the SQL language. The process of creating a logical database design using this model uses a methodical approach known as normalization. The goal of normalization is to ensure that each elementary "fact" is only recorded in one place, so that insertions, updates, and deletions automatically maintain consistency.
The final stage of database design is to make the decisions that affect performance, scalability, recovery, security, and the like, which depend on the particular DBMS. This is often called physical database design, and the output is the physical data model. A key goal during this stage is data independence, meaning that the decisions made for performance optimization purposes should be invisible to end-users and applications. There are two types of data independence: Physical data independence and logical data independence. Physical design is driven mainly by performance requirements, and requires a good knowledge of the expected workload and access patterns, and a deep understanding of the features offered by the chosen DBMS.
Another aspect of physical database design is security. It involves both defining access control to database objects as well as defining security levels and methods for the data itself.
=== Models ===
A database model is a type of data model that determines the logical structure of a database and fundamentally determines in which manner data can be stored, organized, and manipulated. The most popular example of a database model is the relational model (or the SQL approximation of relational), which uses a table-based format.
Common logical data models for databases include:
Navigational databases
Hierarchical database model
Network model
Graph database
Relational model
Entity–relationship model
Enhanced entity–relationship model
Object model
Document model
Entity–attribute–value model
Star schema
An object–relational database combines the two related structures.
Physical data models include:
Inverted index
Flat file
Other models include:
Multidimensional model
Array model
Multivalue model
Specialized models are optimized for particular types of data:
XML database
Semantic model
Content store
Event store
Time series model
=== External, conceptual, and internal views ===
A database management system provides three views of the database data:
The external level defines how each group of end-users sees the organization of data in the database. A single database can have any number of views at the external level.
The conceptual level (or logical level) unifies the various external views into a compatible global view. It provides the synthesis of all the external views. It is out of the scope of the various database end-users, and is rather of interest to database application developers and database administrators.
The internal level (or physical level) is the internal organization of data inside a DBMS. It is concerned with cost, performance, scalability and other operational matters. It deals with storage layout of the data, using storage structures such as indexes to enhance performance. Occasionally it stores data of individual views (materialized views), computed from generic data, if performance justification exists for such redundancy. It balances all the external views' performance requirements, possibly conflicting, in an attempt to optimize overall performance across all activities.
While there is typically only one conceptual and internal view of the data, there can be any number of different external views. This allows users to see database information in a more business-related way rather than from a technical, processing viewpoint. For example, a financial department of a company needs the payment details of all employees as part of the company's expenses, but does not need details about employees that are in the interest of the human resources department. Thus different departments need different views of the company's database.
The three-level database architecture relates to the concept of data independence which was one of the major initial driving forces of the relational model. The idea is that changes made at a certain level do not affect the view at a higher level. For example, changes in the internal level do not affect application programs written using conceptual level interfaces, which reduces the impact of making physical changes to improve performance.
The conceptual view provides a level of indirection between internal and external. On the one hand it provides a common view of the database, independent of different external view structures, and on the other hand it abstracts away details of how the data are stored or managed (internal level). In principle every level, and even every external view, can be presented by a different data model. In practice usually a given DBMS uses the same data model for both the external and the conceptual levels (e.g., relational model). The internal level, which is hidden inside the DBMS and depends on its implementation, requires a different level of detail and uses its own types of data structure types.
== Research ==
Database technology has been an active research topic since the 1960s, both in academia and in the research and development groups of companies (for example IBM Research). Research activity includes theory and development of prototypes. Notable research topics have included models, the atomic transaction concept, related concurrency control techniques, query languages and query optimization methods, RAID, and more.
The database research area has several dedicated academic journals (for example, ACM Transactions on Database Systems-TODS, Data and Knowledge Engineering-DKE) and annual conferences (e.g., ACM SIGMOD, ACM PODS, VLDB, IEEE ICDE).
== See also ==
== Notes ==
== References ==
== Sources ==
== Further reading ==
Ling Liu and Tamer M. Özsu (Eds.) (2009). "Encyclopedia of Database Systems, 4100 p. 60 illus. ISBN 978-0-387-49616-0.
Gray, J. and Reuter, A. Transaction Processing: Concepts and Techniques, 1st edition, Morgan Kaufmann Publishers, 1992.
Kroenke, David M. and David J. Auer. Database Concepts. 3rd ed. New York: Prentice, 2007.
Raghu Ramakrishnan and Johannes Gehrke, Database Management Systems.
Abraham Silberschatz, Henry F. Korth, S. Sudarshan, Database System Concepts.
Lightstone, S.; Teorey, T.; Nadeau, T. (2007). Physical Database Design: the database professional's guide to exploiting indexes, views, storage, and more. Morgan Kaufmann Press. ISBN 978-0-12-369389-1.
Teorey, T.; Lightstone, S. and Nadeau, T. Database Modeling & Design: Logical Design, 4th edition, Morgan Kaufmann Press, 2005. ISBN 0-12-685352-5.
CMU Database courses playlist
MIT OCW 6.830 | Fall 2010 | Database Systems
Berkeley CS W186
== External links ==
DB File extension – information about files with the DB extension | In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an application associated with the database.
Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases spans formal techniques and practical considerations, including data modeling, efficient data representation and storage, query languages, security and privacy of sensitive data, and distributed computing issues, including supporting concurrent access and fault tolerance.
Computer scientists may classify database management systems according to the database models that they support. Relational databases became dominant in the 1980s. These model data as rows and columns in a series of tables, and the vast majority use SQL for writing and querying data. In the 2000s, non-relational databases became popular, collectively referred to as NoSQL, because they use different query languages. | 9 |
325 | empanada | empanada (wiktionary) | Borrowed from Spanish empanada, past participle of empanar (“to wrap in bread”).
IPA(key): /ɛmpəˈnɑːdə/
Rhymes: -ɑːdə
empanada (plural empanadas)
Any of a variety of stuffed pastries found in Spanish, Filipino, and Latin American cuisine.
empanadilla
empanada on Wikipedia.Wikipedia
From Old Galician-Portuguese enpãada, enpanada (13th century: Cantigas de Santa Maria), from *empãar (“to put into bread”). Perhaps under the influence of empanar (“to conceal”, literally “to put into a cloth”). Cognate with Portuguese empada.
IPA(key): /empaˈnaða̝/
empanada f (plural empanadas)
(cooking) pie; traditional stuffed pastry usually composed of two crusts of fine bread and a filling of sauté of vegetables and either meat or fish
petada
empanadilla
empanar
empanada f sg
feminine singular of empanado
empanada on the Galician Wikipedia.Wikipedia gl
Ernesto González Seoane, María Álvarez de la Granja, Ana Isabel Boullón Agrelo (2006–2022) “empanada”, in Dicionario de Dicionarios do galego medieval (in Galician), Santiago de Compostela: ILG
Xavier Varela Barreiro, Xavier Gómez Guinovart (2006–2018) “empaada”, in Corpus Xelmírez - Corpus lingüístico da Galicia medieval (in Galician), Santiago de Compostela: ILG
“empanada” in Dicionario de Dicionarios da lingua galega, SLI - ILGA 2006–2013.
“empanada” in Tesouro informatizado da lingua galega. Santiago: ILG.
“empanada” in Álvarez, Rosario (coord.): Tesouro do léxico patrimonial galego e portugués, Santiago de Compostela: Instituto da Lingua Galega.
empanada f sg
feminine singular of empanado
From empanar (“to bread”).
IPA(key): /empaˈnada/ [ẽm.paˈna.ð̞a]
Rhymes: -ada
Syllabification: em‧pa‧na‧da
empanada f (plural empanadas)
empanada
(colloquial) fraud
→ Belizean Creole: panaades (from the plural form)
→ English: empanada
empanada f sg
feminine singular of empanado
empanada f sg
feminine singular of empanado
“empanado”, in Diccionario de la lengua española, Vigésima tercera edición, Real Academia Española, 2014
impanada
panada
Borrowed from Spanish empanada. Compare Manado Malay panada.
(Standard Tagalog) IPA(key): /ʔempaˈnada/ [ʔɛm.pɐˈn̪aː.d̪ɐ]
Rhymes: -ada
Syllabification: em‧pa‧na‧da
empanada (Baybayin spelling ᜁᜋ᜔ᜉᜈᜇ)
empanada (especially Philippine varieties) | Borrowed from Spanish empanada, past participle of empanar (“to wrap in bread”).
IPA(key): /ɛmpəˈnɑːdə/
Rhymes: -ɑːdə
empanada (plural empanadas)
Any of a variety of stuffed pastries found in Spanish, Filipino, and Latin American cuisine.
empanadilla
empanada on Wikipedia.Wikipedia
From Old Galician-Portuguese enpãada, enpanada (13th century: Cantigas de Santa Maria), from *empãar (“to put into bread”). Perhaps under the influence of empanar (“to conceal”, literally “to put into a cloth”). Cognate with Portuguese empada.
IPA(key): /empaˈnaða̝/
empanada f (plural empanadas)
(cooking) pie; traditional stuffed pastry usually composed of two crusts of fine bread and a filling of sauté of vegetables and either meat or fish
petada
empanadilla
empanar
empanada f sg
feminine singular of empanado
empanada on the Galician Wikipedia.Wikipedia gl
Ernesto González Seoane, María Álvarez de la Granja, Ana Isabel Boullón Agrelo (2006–2022) “empanada”, in Dicionario de Dicionarios do galego medieval (in Galician), Santiago de Compostela: ILG
Xavier Varela Barreiro, Xavier Gómez Guinovart (2006–2018) “empaada”, in Corpus Xelmírez - Corpus lingüístico da Galicia medieval (in Galician), Santiago de Compostela: ILG
“empanada” in Dicionario de Dicionarios da lingua galega, SLI - ILGA 2006–2013.
“empanada” in Tesouro informatizado da lingua galega. Santiago: ILG.
“empanada” in Álvarez, Rosario (coord.): Tesouro do léxico patrimonial galego e portugués, Santiago de Compostela: Instituto da Lingua Galega.
empanada f sg
feminine singular of empanado
From empanar (“to bread”).
IPA(key): /empaˈnada/ [ẽm.paˈna.ð̞a]
Rhymes: -ada
Syllabification: em‧pa‧na‧da
empanada f (plural empanadas)
empanada
(colloquial) fraud
→ Belizean Creole: panaades (from the plural form)
→ English: empanada
empanada f sg
feminine singular of empanado
empanada f sg
feminine singular of empanado
“empanado”, in Diccionario de la lengua española, Vigésima tercera edición, Real Academia Española, 2014
impanada
panada
Borrowed from Spanish empanada. Compare Manado Malay panada.
(Standard Tagalog) IPA(key): /ʔempaˈnada/ [ʔɛm.pɐˈn̪aː.d̪ɐ]
Rhymes: -ada
Syllabification: em‧pa‧na‧da
empanada (Baybayin spelling ᜁᜋ᜔ᜉᜈᜇ)
empanada (especially Philippine varieties) | 38 |
326 | empanada | Empanada (wikipedia) | An empanada is a type of baked or fried turnover consisting of pastry and filling, common in Spain, other Southern European countries, Latin American countries, and the Philippines. The name comes from the Spanish empanar (to bread, i.e., to coat with bread), and translates as 'breaded', that is, wrapped or coated in bread. They are made by folding dough over a filling, which may consist of meat, cheese, tomato, corn, or other ingredients, and then cooking the resulting turnover, either by baking or frying.
== Origins ==
The origin of empanadas is unknown, but they are thought to have originated in 7th century Galicia, a region in northwest Spain.
An empanada (empãada) is mentioned in the Cantigas de Santa Maria 57:VI (c. 1282):Entr' esses roubadores / viu jazer um vilão / desses mais malfeitores, / ũa perna na mão / de galinha, freame / que sacara com fame / entom dũ' empãada | que so um seu çurame/ comer quisera, / mais nom podera, / ca Deus nom queria.
In the midst of these robbers he saw lying there one of the most vicious of the rascals with a chicken leg in his hand. He had taken the cold morsel out of a pasty and was about to eat it under the cover of his cape. However, he could not, for God prevented it.Rabbinic Jewish books from the same period, including the Novellae of Asher ben Jehiel (1250-1327), the Novellae of Yom Tov of Seville (c. 1260–1320), the Orchot Chayyim of Aaron ben Jacob (c. 1250-1325) and the Arba'ah Turim of Jacob ben Asher (c. 1270-1340) mention "inpanada" and "panada" as bread products containing fat, meat or fish on the inside.
A cookbook published in Catalan in 1520, Llibre del Coch by Robert de Nola, mentions empanadas filled with seafood in the recipes for Catalan, Italian, French, and Arabian food.
== By country and region ==
=== Argentina ===
Argentine empanadas are often served during parties and festivals as a starter or main course. Shops specialize in freshly made empanadas, with many flavors and fillings.
Every region of Argentina has its own characteristic variant. Those of Salta (salteñas) are small, juicy and spicy, and contain potatoes, peppers and ground chili. These are also popular in neighbouring Bolivia.
The Jujuy variant adds peas and garlic. Its filling is called recado and the repulgue (method of closing the empanada) simbado. The La Rioja variant includes hard-boiled egg, red bell pepper, olives, and raisins. In Jujuy, there are two variants: criollas and arabes. Those of Santiago are considered especially juicy. Those of Catamarca are similar but smaller. Tucumán is known for the empanada creole; an annual National Empanada festival is held in Famaillá. Those of Famaillá are made with matambre and fried in good fat, competing with the entreveradas (mixed-grated), in which the matambre is mixed with chicken breast, garlic, ground chili, hard-boiled egg and cumin. Those of Mendoza are large and include olives and garlic. Those of San Juan have a higher proportion of onion, making them juicier and slightly sweet. Olives are also common and sometimes fat is also added to the recado or the dough. In San Luis they are big, seasoned with oregano and hot pepper, and kneaded with pork fat. In Córdoba, they were called "federal cake" or empanadas de Misia Manuelita, famous because pears boiled in wine with cloves were added to their filling. Today they are not so sweet but it is tradition to sprinkle them with sugar. In Traslasierra they add carrots and potatoes. In the Litoral, where immigrants from various parts of the world predominated, Santa Fe, Entre Ríos and Corrientes fill them with river fish, such as surubí (catfish) or dorado, or with white sauce and Goya cheese. In the Cordillera of Patagonia, they are made with lamb and on the coast with seafood. In Buenos Aires, the Creole empanada is so important that it has been declared a Cultural Heritage of Food and Gastronomy by the Argentine Ministry of Culture.
=== Belize ===
In Belize, empanadas are known as panades. They are made with masa (corn dough) and typically stuffed with fish, chicken, or beans. They are usually deep fried and served with a cabbage or salsa topping. Panades are frequently sold as street food.
=== Brazil ===
In Brazil, an empanada is called a pastel (pl.: pastéis) and consists of half-circle or rectangle-shaped thin crust pies with assorted fillings, fried in vegetable oil. The result is a crispy, brownish fried pie. The most common fillings are ground meat, mozzarella, catupiry, heart of palm, codfish, cream cheese, chicken and small shrimp. Pastéis with sweet fillings such as guava paste with Minas cheese, banana and chocolate also exist.
=== Chile ===
Empanadas are a staple part of Chilean cuisine. Commonly consumed in large quantities during the country's national day celebrations, many Chileans consider this to be their most representative dish. The most iconic variety is the oven-baked empanada de pino, which is filled with ground beef, minced onion, half or a quarter of a hard-boiled egg, and a single unpitted black olive.
Empanadas in Chile are eaten year-round and are either oven-baked or deep-fried; the latter is a popular street food.
=== Costa Rica ===
In Costa Rica, an empanada is turnover usually made with nixtamalized (lime treated) masa (corn dough); nevertheless, it could be made with doughs of cassava (yuca), green or ripe plantain, in addition to wheat flour. The empanada can be pan fried, deep fried or baked.
The empanada can be filled with plenty of foods, although beef, pork or chicken meat, but also with cheese, palm heart or different kind of vegetable hashes (called picadillo) or refried beans are the most common ones. There are also sweet empanadas filled with tropical fruit marmalades (such as guava or pineapple), dulce de chiverre (a sweet jam of Cucurbita ficifolia, also known as chilacayote, alcayota, calabaza de cabello de ángel or cidra) or dulce de leche (manjar, arequipe or cajeta).
In the caribbean coast of Costa Rica, there are some kind of wheat flour empanadas similar to Jamaican beef patty, also found with chicken meat or vegetable filling (usually ackee); there are also sweet empanadas called "Plantain Tart" or "Plantintá" (made with ripe plantain jam filling) and "Pineapple Tart" (made with pineapple jam filling).
=== Cuba ===
In Cuba, empanadas are frequently enjoyed as snacks, appetizers, or main courses at parties and gatherings. In Havana, the most common variant is filled with picadillo or shredded chicken, often mixed with ingredients like cumin, garlic, onions, raisins, and green olives. Empanadas are also commonly eaten for dessert, including fillings such as guava paste and cream cheese. In Cuban cuisine, empanadas are almost always deep-fried.
=== Ecuador ===
Empanadas de viento or "windy" empanadas are fried, wheat-based empanadas stuffed with stringy cheese and sprinkled with sugar. They have been given this appellation for their inflated appearance as if they have been filled with air. Empanadas de viento can be made in cocktail size, appetiser size, and giant size, which is popular among the middle and working class. They are often eaten with coffee or with té de hierba luisa or lemon verbena tea. Their appearance is very similar to an Italian panzerotto.
Empanadas can be purchased from food stalls, markets, and restaurants. During religious holidays, women from the countryside fry empanadas at home and sell them in front of churches.
Empanadas de verde or plantain empanadas are plantain-based and filled with cheese and fried. These empanadas are most commonly found in the coastal regions of the country.
With the growth of Southern Cone and Colombian immigrants, wheat- and meat-based baked empanadas and corn-based empanadas have also become popular.
=== El Salvador ===
El Salvador is one of few countries where the empanada is made with plantain rather than a flour-based dough wrapping. A popular sweet variation, empanadas de platano are torpedo-shaped dumplings of dough made from very ripe plantains, filled with vanilla custard, fried, then rolled in sugar. They may alternatively have a filling made from refried beans rather than milk-based custard, but the flavour profile remains sweet rather than savoury.
=== France ===
In France, the traditional chaussons are made with a puff pastry dough filled with stew such as daube or confit, or a bechamel sauce mixed with ham and/or cheese. They also exist in sweet version (see chausson aux pommes). They are half-moon shaped. If the shape is rectangular they receive the name of friand. One regional version is the pâté lorrain, filled with pork meat cooked with wine and onions. All these versions are baked.
The fried versions can be made of puff pastry or shortcrust pastry and are called rissoles. The most famous is the rissole de Coucy, filled with meat or fish.
=== India ===
Gujhia is similar to a sweet empanada, in a half moon shape.
Samosa is a stuffed savory pastry.
=== Indonesia ===
In Indonesia, empanadas are known as panada. They are especially popular in Manado cuisine of North Sulawesi where their panada has a thick crust made from fried bread, filled with spicy cakalang fish (skipjack tuna) and chili, curry, potatoes or quail eggs. The panada in North Sulawesi was derived from Portuguese influence in the region. The dish is similar to karipap and pastel, although they have a thinner crust compared to panada.
=== Italy ===
The Sicilian 'mpanatigghi are stuffed, consisting of half-moon-shaped panzerotti filled with a mixture of almonds, walnuts, chocolate, sugar, cinnamon, cloves and minced beef. These are typical of Modica, in the province of Ragusa, Sicily. They are also known by the italianized word impanatiglie or dolce di carne (pasty of meat).
They were probably introduced by the Spaniards during their rule in Sicily which took place in the sixteenth century; this is suggested by the etymology of the name which comes from the Spanish empanadas or empanadillas, as well as the somewhat unusual combination of meat and chocolate, which occurs occasionally in Spanish cuisine. In previous centuries, game meat was used in 'mpanatigghi; today beef is used.
=== Philippines ===
Filipino empanadas usually contain ground beef, pork or chicken, potatoes, chopped onions, and raisins (picadillo-style), in a somewhat sweet, wheat flour bread. There are two kinds available: the baked sort and the flaky fried type. To lower costs, potatoes are often added as an extender, while another filling is kutsay (garlic chives).
Empanadas in the northern part of the Ilocos usually have savoury fillings of green papaya, mung beans, and sometimes chopped Ilocano sausage (chorizo) or longaniza and egg yolk. This particular variant is fried and uses rice flour for a crunchier shell. Empanadas can also be filled with mashed eggplant, scrambled eggs, and cabbage, which is called poqui poqui.
In Bulacan, empanada de kaliskis (lit. 'fish scale empanada'), uniquely has a flaky multilayered crust resembling scales, hence the name. In Cebu, empanada Danao is a characteristically sweet-savory variant. It is filled with chopped chorizo and chayote, deep-fried, and dusted in white sugar before serving. In Zamboanga, empanada Zamboangueño is filled with chopped sweet potato, garbanzo beans, and served with a sweet vinegar dipping sauce.
Dessert versions of empanadas also exist, notably empanaditas, which commonly have a filling of latik (coconut caramel), honey and nuts, or peanut butter. Kapampangan versions of empanaditas have a yema (custard) and cashew nut filling. In Cebu, sinudlan empanada is a small deep-fried empanada with bukayo (sweetened coconut meat) filling.
=== Puerto Rico ===
In Puerto Rico, empanadas are made of a flour base and fried, known either as empanadillas or pastelillos- a hotly debated topic usually dependent on the region of the island and/or the type of border on the pastry.
Common fillings include meat such as ground beef, pork, chicken, pizza (tomato paste and cheese), guava and cheese, jueyes (crab), chapín (Spotted trunkfish), rabbit, octopus, conch, and much more depending on local cuisine.
=== United States ===
Empanadas, mainly based on South American recipes, are widely available in New York City, New Jersey, Baltimore, Philadelphia, Washington, D.C., and Miami from food carts, food trucks, and restaurants. Empanadas are usually found in U.S. areas with a large Hispanic population, such as San Antonio, Los Angeles, and San Francisco.
=== Venezuela ===
Traditional Venezuelan empanadas are made with ground corn dough, though modern versions are made with precooked corn. The dough may have a yellow color when toasted due to the addition of annatto. The fillings are very diverse, with the most conventional being cheese, shredded beef, chicken, cazón (school shark) in the Margaritan Island region especially, ham, black beans and cheese (commonly called dominó) and even combinations of mollusks. The empanadas have a half-moon shape and are fried in oil. Sometimes, they may have more than one filling, such as in empanadas de pabellón, which are made with a shredded beef filling (or cazón in the Margarita Island region), black beans, slices of fried plantain, and shredded white cheese.
== Similar foods ==
The empanada resembles savory pastries found in many other cultures, such as the molote, pirozhki, calzone, samosa, knish, kreatopitakia, khuushuur, Jamaican patty and pasty.
In most Malay-speaking countries in Southeast Asia, the pastry is commonly called epok-epok or karipap (English: curry puff). Fried dumplings are found in Chinese cuisine (jiaozi) and in Vietnamese cuisine (bánh gối).
== References == | An empanada is a type of baked or fried turnover consisting of pastry and filling, common in Spain, other Southern European countries, Latin American countries, and the Philippines. The name comes from the Spanish empanar (to bread, i.e., to coat with bread), and translates as 'breaded', that is, wrapped or coated in bread. They are made by folding dough over a filling, which may consist of meat, cheese, tomato, corn, or other ingredients, and then cooking the resulting turnover, either by baking or frying.
| 2 |
327 | hub airport | Airline hub (wikipedia) | An airline hub or hub airport is an airport used by one or more airlines to concentrate passenger traffic and flight operations. Hubs serve as transfer (or stop-over) points to help get passengers to their final destination. It is part of the hub-and-spoke system. An airline may operate flights from several non-hub (spoke) cities to the hub airport, and passengers traveling between spoke cities connect through the hub. This paradigm creates economies of scale that allow an airline to serve (via an intermediate connection) city-pairs that could otherwise not be economically served on a non-stop basis. This system contrasts with the point-to-point model, in which there are no hubs and nonstop flights are instead offered between spoke cities. Hub airports also serve origin and destination (O&D) traffic.
== Operations ==
The hub-and-spoke system allows an airline to serve fewer routes, so fewer aircraft are needed. The system also increases passenger loads; a flight from a hub to a spoke carries not just passengers originating at the hub, but also passengers originating at multiple spoke cities. However, the system is costly. Additional employees and facilities are needed to cater to connecting passengers. To serve spoke cities of varying populations and demand, an airline requires several aircraft types, and specific training and equipment are necessary for each type. In addition, airlines may experience capacity constraints as they expand at their hub airports.
For the passenger, the hub-and-spoke system offers one-stop air service to a wide array of destinations. However, it requires having to regularly make connections en route to their final destination, which increases travel time. Additionally, airlines can come to monopolise their hubs (fortress hubs), allowing them to freely increase fares as passengers have no alternative. High domestic connectivity in the United States is achieved through airport location and hub dominance. The top 10 megahubs in the US are dominated by American Airlines, Delta Air Lines and United Airlines, the three largest United States-based airlines.
=== Banking ===
Airlines may operate banks of flights at their hubs, in which several flights arrive and depart within short periods of time. The banks may be known as "peaks" of activity at the hubs and the non-banks as "valleys". Banking allows for short connection times for passengers. However, an airline must assemble many resources to cater to the influx of flights during a bank, and having several aircraft on the ground at the same time can lead to congestion and delays. In addition, banking could result in inefficient aircraft utilisation, with aircraft waiting at spoke cities for the next bank.
Instead, some airlines have debanked their hubs, introducing a "rolling hub" in which flight arrivals and departures are spread throughout the day. This phenomenon is also known as "depeaking". While costs may decrease, connection times are longer at a rolling hub. American Airlines was the first to depeak its hubs, trying to improve profitability following the September 11 attacks. It rebanked its hubs in 2015, however, feeling the gain in connecting passengers would outweigh the rise in costs.
For example, the hub of Qatar Airways in Doha Airport has 471 daily movements to 140 destinations by March 2020 with an average of 262 seats per movement; in three main waves: 05:00–09:00 (132 movements), 16:00–21:00 (128) and 23:00–03:00 (132), allowing around 30 million connecting passengers in 2019.
== History ==
=== United States ===
Before the US airline industry was deregulated in 1978, most airlines operated under the point-to-point system (with a notable exception being Pan Am). The Civil Aeronautics Board dictated which routes an airline could fly. At the same time, however, some airlines began to experiment with the hub-and-spoke system. Delta Air Lines was the first to implement such a system, providing service to remote spoke cities from its Atlanta hub. After deregulation, many airlines quickly established hub-and-spoke route networks of their own.
=== Middle East ===
In 1974, the governments of Bahrain, Oman, Qatar and the United Arab Emirates took control of Gulf Air from the British Overseas Airways Corporation (BOAC). Gulf Air became the flag carrier of the four Middle Eastern nations. It linked Oman, Qatar and the UAE to its Bahrain hub, from which it offered flights to destinations throughout Europe and Asia. In the UAE, Gulf Air focused on Abu Dhabi rather than Dubai, contrary to the aspirations of UAE Prime Minister Mohammed bin Rashid Al Maktoum to transform the latter into a world-class metropolis. Sheikh Mohammed proceeded to establish a new airline based in Dubai, Emirates, which launched operations in 1985.
Elsewhere in the Middle East region, Qatar and Oman decided to create their own airlines as well. Qatar Airways and Oman Air were both founded in 1993, with hubs at Doha and Muscat respectively. As the new airlines grew, their home nations relied less on Gulf Air to provide air service. Qatar withdrew its share in Gulf Air in 2002. In 2003, the UAE formed another national airline, Etihad Airways, which is based in Abu Dhabi. The country exited Gulf Air in 2006, and Oman followed in 2007. Gulf Air therefore became fully owned by the government of Bahrain.
Emirates, Qatar Airways, Saudia and Etihad Airways have since established large hubs at their respective home airports. The hubs, which benefit from their proximity to large population centres, have become popular stopover points on trips between Europe and Asia, for example. Their rapid growth has impacted the development of traditional hubs, such as London-Heathrow, Paris-Charles de Gaulle, and New York-JFK.
== Types of hubs ==
=== Cargo hubs and scissor hubs ===
A cargo hub is an airport that primarily is operated by a cargo airline that uses the hub-and-spoke system. In the United States, two of the largest cargo hub airports, FedEx's Memphis Superhub and UPS Louisville Worldport, are close to the mean center of the United States population. FedEx's airline, FedEx Express, established its Memphis hub in 1973, prior to the deregulation of the air cargo industry in the United States. The system has created an efficient delivery system for the airline. UPS Airlines has followed a similar pattern in Louisville. In Europe, ASL Airlines, Cargolux and DHL Aviation follow a similar strategy and operate their primary hubs at Liège, Luxembourg and Leipzig respectively.
Additionally, Ted Stevens International Airport in Anchorage, Alaska, is a frequent stop-over hub for many cargo airlines flying between Asia and North America. Most cargo airlines only stop in Anchorage for refueling and customs, but FedEx and UPS frequently use Anchorage to sort trans-pacific packages between regional hubs on each continent in addition to refueling and customs.
Passenger airlines that operate in a similar manner to the FedEx and UPS hubs are often regarded as scissor hubs, as many flights to one destination all land and deplane passengers simultaneously and, after a passenger transit period, repeat a similar process for departure to the final destination of each plane. In past, Air India operated a scissor hub at London's Heathrow Airport, where passengers from Delhi, Ahmedabad, and Mumbai could continue onto a flight to Newark. Until its grounding, Jet Airways operated a similar scissor hub at Amsterdam Airport Schiphol to transport passengers from Bangalore, Mumbai and Delhi to Toronto-Pearson and vice versa. At the peak of operations at their former scissor hub at Brussels prior to the 2016 shift to Schiphol, flights operated from Mumbai, Delhi, and Chennai and continued onward to Toronto, New York, and Newark after a near-simultaneous stopover in Brussels and vice versa. An international scissor hub could be used for third and fourth freedom flights or it could be used for fifth freedom flights, for which a precursor is a bilateral treaty between two country pairs.
WestJet used to utilize St. John's as a scissor hub during its summer schedule for flights inbound from Ottawa, Toronto, and Orlando and outbound to Dublin and London–Gatwick. Qantas similarly used to utilize Los Angeles International Airport as a scissor hub for flights inbound from Melbourne, Brisbane or Sydney, where passengers could connect onwards if traveling to New York–JFK.
=== Focus city ===
In the airline industry, a focus city is a destination from which an airline operates limited point-to-point routes. A focus city primarily caters to the local market rather than to connecting passengers.
Although the term focus city is used to mainly refer to an airport from which an airline operates limited point-to-point routes, its usage has loosely expanded to refer to a small-scale hub as well. For example, even though JetBlue's operations at New York–JFK resemble that of a hub, the airline still refers to it as a focus city.
=== Fortress hub ===
A fortress hub exists when an airline controls a significant majority of the market at one of its hubs. Competition is particularly difficult at fortress hubs. As of 2012, examples included Delta Air Lines at Atlanta, Detroit, Minneapolis/St. Paul and Salt Lake City; American Airlines at Charlotte, Dallas Fort Worth, Miami, and Philadelphia; and United Airlines at Houston–Intercontinental, Newark and Washington-Dulles.
Flag carriers have historically enjoyed similar dominance at the main international airport of their countries and some still do. Examples include Aeromexico in Mexico City, Air Canada in Toronto–Pearson, Air France in Paris–Charles de Gaulle, British Airways in London–Heathrow, Cathay Pacific in Hong Kong, Copa Airlines in Panama City, Emirates in Dubai, Ethiopian Airlines in Addis Ababa, Finnair in Helsinki, Iberia in Madrid, Japan Airlines in Tokyo-Haneda, Iran Air in Imam Khomeini, ITA Airways in Rome, Aeroflot in Sheremetyevo, Korean Air at Seoul–Incheon, KLM in Amsterdam, Lufthansa in Frankfurt, Qantas in Sydney, Qatar Airways in Doha, Singapore Airlines in Singapore, South African Airways in Johannesburg, Swiss International Air Lines in Zurich, Turkish Airlines in Istanbul, WestJet in Calgary and Aegean Airlines in Athens.
=== Primary and secondary hubs ===
A primary hub is the main hub for an airline. However, as an airline expands operations at its primary hub to the point that it experiences capacity limitations, it may elect to open secondary hubs. Examples of such hubs are Air Canada's hubs at Montréal–Trudeau and Vancouver, British Airways' hub at London–Gatwick, Air India's hub at Mumbai and Lufthansa's hub at Munich. By operating multiple hubs, airlines can expand their geographic reach. They can also better serve spoke–spoke markets, providing more itineraries with connections at different hubs.
Cargo airlines like FedEx Express and UPS Airlines also operate secondary hubs to an extent, but these are primarily used to serve regional high-demand destinations because shipping packages through its main hub would waste fuel; an example of this would be FedEx transiting a package through Oakland International Airport when shipping packages between destinations near Seattle and Phoenix, Arizona instead of sending deliveries through the Memphis Superhub.
=== Reliever hub ===
A given hub's capacity may become exhausted or capacity shortages may occur during peak periods of the day, at which point airlines may be compelled to shift traffic to a reliever hub. A reliever hub has the potential to serve several functions for an airline: it can bypass the congested hub, it can absorb excess demand for flights that could otherwise not be scheduled at the congested hub, and it can schedule new O&D city pairs for connecting traffic.
One of the most recognized examples of this model is Delta Air Lines' and American Airlines' uses of LaGuardia Airport as a domestic hub in New York City, due to capacity and slot restrictions at their hubs at John F. Kennedy International Airport. Many regional flights operate out of LaGuardia, while most international and long-haul domestic flights remain at JFK.
Lufthansa operates a similar model of business with its hubs at Frankfurt Airport and Munich Airport. Generally speaking, a marginal majority of the airline's long-haul flights are based out of Frankfurt, while a similarly-sized but smaller minority are based out of Munich.
=== Moonlight hub ===
In past history, carriers have maintained niche, time-of-day operations at hubs. The most notable was America West's use of McCarran International Airport (now named after longtime Nevada Senator Harry Reid) in Las Vegas as a primary night-flight hub to increase aircraft utilization rates far beyond those of competing carriers.
== See also ==
Hidden city ticketing
List of former airline hubs
List of hub airports
Point-to-point transit
Transport hub
== Notes ==
== References == | An airline hub or hub airport is an airport used by one or more airlines to concentrate passenger traffic and flight operations. Hubs serve as transfer (or stop-over) points to help get passengers to their final destination. It is part of the hub-and-spoke system. An airline may operate flights from several non-hub (spoke) cities to the hub airport, and passengers traveling between spoke cities connect through the hub. This paradigm creates economies of scale that allow an airline to serve (via an intermediate connection) city-pairs that could otherwise not be economically served on a non-stop basis. This system contrasts with the point-to-point model, in which there are no hubs and nonstop flights are instead offered between spoke cities. Hub airports also serve origin and destination (O&D) traffic. | 6 |
328 | hebb synapse | Hebbian theory (wikipedia) | Hebbian theory is a neuropsychological theory claiming that an increase in synaptic efficacy arises from a presynaptic cell's repeated and persistent stimulation of a postsynaptic cell. It is an attempt to explain synaptic plasticity, the adaptation of brain neurons during the learning process. It was introduced by Donald Hebb in his 1949 book The Organization of Behavior. The theory is also called Hebb's rule, Hebb's postulate, and cell assembly theory. Hebb states it as follows:
Let us assume that the persistence or repetition of a reverberatory activity (or "trace") tends to induce lasting cellular changes that add to its stability. ... When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased.
The theory is often summarized as "Neurons that fire together, wire together." However, Hebb emphasized that cell A needs to "take part in firing" cell B, and such causality can occur only if cell A fires just before, not at the same time as, cell B. This aspect of causation in Hebb's work foreshadowed what is now known about spike-timing-dependent plasticity, which requires temporal precedence.
The theory attempts to explain associative or Hebbian learning, in which simultaneous activation of cells leads to pronounced increases in synaptic strength between those cells. It also provides a biological basis for errorless learning methods for education and memory rehabilitation. In the study of neural networks in cognitive function, it is often regarded as the neuronal basis of unsupervised learning.
== Hebbian engrams and cell assembly theory ==
Hebbian theory concerns how neurons might connect themselves to become engrams. Hebb's theories on the form and function of cell assemblies can be understood from the following:: 70
The general idea is an old one, that any two cells or systems of cells that are repeatedly active at the same time will tend to become 'associated' so that activity in one facilitates activity in the other.
Hebb also wrote:: 63
When one cell repeatedly assists in firing another, the axon of the first cell develops synaptic knobs (or enlarges them if they already exist) in contact with the soma of the second cell.
[D. Alan Allport] posits additional ideas regarding cell assembly theory and its role in forming engrams, along the lines of the concept of auto-association, described as follows:
If the inputs to a system cause the same pattern of activity to occur repeatedly, the set of active elements constituting that pattern will become increasingly strongly inter-associated. That is, each element will tend to turn on every other element and (with negative weights) to turn off the elements that do not form part of the pattern. To put it another way, the pattern as a whole will become 'auto-associated'. We may call a learned (auto-associated) pattern an engram.: 44
Work in the laboratory of Eric Kandel has provided evidence for the involvement of Hebbian learning mechanisms at synapses in the marine gastropod Aplysia californica. Experiments on Hebbian synapse modification mechanisms at the central nervous system synapses of vertebrates are much more difficult to control than are experiments with the relatively simple peripheral nervous system synapses studied in marine invertebrates. Much of the work on long-lasting synaptic changes between vertebrate neurons (such as long-term potentiation) involves the use of non-physiological experimental stimulation of brain cells. However, some of the physiologically relevant synapse modification mechanisms that have been studied in vertebrate brains do seem to be examples of Hebbian processes. One such study reviews results from experiments that indicate that long-lasting changes in synaptic strengths can be induced by physiologically relevant synaptic activity working through both Hebbian and non-Hebbian mechanisms.
== Principles ==
From the point of view of artificial neurons and artificial neural networks, Hebb's principle can be described as a method of determining how to alter the weights between model neurons. The weight between two neurons increases if the two neurons activate simultaneously, and reduces if they activate separately. Nodes that tend to be either both positive or both negative at the same time have strong positive weights, while those that tend to be opposite have strong negative weights.
The following is a formulaic description of Hebbian learning: (many other descriptions are possible)
w
i
j
=
x
i
x
j
{\displaystyle \,w_{ij}=x_{i}x_{j}}
where
w
i
j
{\displaystyle w_{ij}}
is the weight of the connection from neuron
j
{\displaystyle j}
to neuron
i
{\displaystyle i}
and
x
i
{\displaystyle x_{i}}
the input for neuron
i
{\displaystyle i}
. Note that this is pattern learning (weights updated after every training example). In a Hopfield network, connections
w
i
j
{\displaystyle w_{ij}}
are set to zero if
i
=
j
{\displaystyle i=j}
(no reflexive connections allowed). With binary neurons (activations either 0 or 1), connections would be set to 1 if the connected neurons have the same activation for a pattern.
When several training patterns are used the expression becomes an average of individual ones:
w
i
j
=
1
p
∑
k
=
1
p
x
i
k
x
j
k
{\displaystyle w_{ij}={\frac {1}{p}}\sum _{k=1}^{p}x_{i}^{k}x_{j}^{k}}
where
w
i
j
{\displaystyle w_{ij}}
is the weight of the connection from neuron
j
{\displaystyle j}
to neuron
i
{\displaystyle i}
,
p
{\displaystyle p}
is the number of training patterns and
x
i
k
{\displaystyle x_{i}^{k}}
the
k
{\displaystyle k}
-th input for neuron
i
{\displaystyle i}
. This is learning by epoch (weights updated after all the training examples are presented), being last term applicable to both discrete and continuous training sets. Again, in a Hopfield network, connections
w
i
j
{\displaystyle w_{ij}}
are set to zero if
i
=
j
{\displaystyle i=j}
(no reflexive connections).
A variation of Hebbian learning that takes into account phenomena such as blocking and many other neural learning phenomena is the mathematical model of Harry Klopf. Klopf's model reproduces a great many biological phenomena, and is also simple to implement.
== Relationship to unsupervised learning, stability, and generalization ==
Because of the simple nature of Hebbian learning, based only on the coincidence of pre- and post-synaptic activity, it may not be intuitively clear why this form of plasticity leads to meaningful learning. However, it can be shown that Hebbian plasticity does pick up the statistical properties of the input in a way that can be categorized as unsupervised learning.
This can be mathematically shown in a simplified example. Let us work under the simplifying assumption of a single rate-based neuron of rate
y
(
t
)
{\displaystyle y(t)}
, whose inputs have rates
x
1
(
t
)
.
.
.
x
N
(
t
)
{\displaystyle x_{1}(t)...x_{N}(t)}
. The response of the neuron
y
(
t
)
{\displaystyle y(t)}
is usually described as a linear combination of its input,
∑
i
w
i
x
i
{\displaystyle \sum _{i}w_{i}x_{i}}
, followed by a response function
f
{\displaystyle f}
:
y
=
f
(
∑
i
=
1
N
w
i
x
i
)
.
{\displaystyle y=f\left(\sum _{i=1}^{N}w_{i}x_{i}\right).}
As defined in the previous sections, Hebbian plasticity describes the evolution in time of the synaptic weight
w
{\displaystyle w}
:
d
w
i
d
t
=
η
x
i
y
.
{\displaystyle {\frac {dw_{i}}{dt}}=\eta x_{i}y.}
Assuming, for simplicity, an identity response function
f
(
a
)
=
a
{\displaystyle f(a)=a}
, we can write
d
w
i
d
t
=
η
x
i
∑
j
=
1
N
w
j
x
j
{\displaystyle {\frac {dw_{i}}{dt}}=\eta x_{i}\sum _{j=1}^{N}w_{j}x_{j}}
or in matrix form:
d
w
d
t
=
η
x
x
T
w
.
{\displaystyle {\frac {d\mathbf {w} }{dt}}=\eta \mathbf {x} \mathbf {x} ^{T}\mathbf {w} .}
As in the previous chapter, if training by epoch is done an average
⟨
…
⟩
{\displaystyle \langle \dots \rangle }
over discrete or continuous (time) training set of
x
{\displaystyle \mathbf {x} }
can be done:where
C
=
⟨
x
x
T
⟩
{\displaystyle C=\langle \,\mathbf {x} \mathbf {x} ^{T}\rangle }
is the correlation matrix of the input under the additional assumption that
⟨
x
⟩
=
0
{\displaystyle \langle \mathbf {x} \rangle =0}
(i.e. the average of the inputs is zero). This is a system of
N
{\displaystyle N}
coupled linear differential equations. Since
C
{\displaystyle C}
is symmetric, it is also diagonalizable, and the solution can be found, by working in its eigenvectors basis, to be of the form
w
(
t
)
=
k
1
e
η
α
1
t
c
1
+
k
2
e
η
α
2
t
c
2
+
.
.
.
+
k
N
e
η
α
N
t
c
N
{\displaystyle \mathbf {w} (t)=k_{1}e^{\eta \alpha _{1}t}\mathbf {c} _{1}+k_{2}e^{\eta \alpha _{2}t}\mathbf {c} _{2}+...+k_{N}e^{\eta \alpha _{N}t}\mathbf {c} _{N}}
where
k
i
{\displaystyle k_{i}}
are arbitrary constants,
c
i
{\displaystyle \mathbf {c} _{i}}
are the eigenvectors of
C
{\displaystyle C}
and
α
i
{\displaystyle \alpha _{i}}
their corresponding eigen values.
Since a correlation matrix is always a positive-definite matrix, the eigenvalues are all positive, and one can easily see how the above solution is always exponentially divergent in time.
This is an intrinsic problem due to this version of Hebb's rule being unstable, as in any network with a dominant signal the synaptic weights will increase or decrease exponentially. Intuitively, this is because whenever the presynaptic neuron excites the postsynaptic neuron, the weight between them is reinforced, causing an even stronger excitation in the future, and so forth, in a self-reinforcing way. One may think a solution is to limit the firing rate of the postsynaptic neuron by adding a non-linear, saturating response function
f
{\displaystyle f}
, but in fact, it can be shown that for any neuron model, Hebb's rule is unstable. Therefore, network models of neurons usually employ other learning theories such as BCM theory, Oja's rule, or the generalized Hebbian algorithm.
Regardless, even for the unstable solution above, one can see that, when sufficient time has passed, one of the terms dominates over the others, and
w
(
t
)
≈
e
η
α
∗
t
c
∗
{\displaystyle \mathbf {w} (t)\approx e^{\eta \alpha ^{*}t}\mathbf {c} ^{*}}
where
α
∗
{\displaystyle \alpha ^{*}}
is the largest eigenvalue of
C
{\displaystyle C}
. At this time, the postsynaptic neuron performs the following operation:
y
≈
e
η
α
∗
t
c
∗
x
{\displaystyle y\approx e^{\eta \alpha ^{*}t}\mathbf {c} ^{*}\mathbf {x} }
Because, again,
c
∗
{\displaystyle \mathbf {c} ^{*}}
is the eigenvector corresponding to the largest eigenvalue of the correlation matrix between the
x
i
{\displaystyle x_{i}}
s, this corresponds exactly to computing the first principal component of the input.
This mechanism can be extended to performing a full PCA (principal component analysis) of the input by adding further postsynaptic neurons, provided the postsynaptic neurons are prevented from all picking up the same principal component, for example by adding lateral inhibition in the postsynaptic layer. We have thus connected Hebbian learning to PCA, which is an elementary form of unsupervised learning, in the sense that the network can pick up useful statistical aspects of the input, and "describe" them in a distilled way in its output.
== Limitations ==
Despite the common use of Hebbian models for long-term potentiation, Hebb's principle does not cover all forms of synaptic long-term plasticity. Hebb did not postulate any rules for inhibitory synapses, nor did he make predictions for anti-causal spike sequences (presynaptic neuron fires after the postsynaptic neuron). Synaptic modification may not simply occur only between activated neurons A and B, but at neighboring synapses as well. All forms of hetero synaptic and homeostatic plasticity are therefore considered non-Hebbian. An example is retrograde signaling to presynaptic terminals. The compound most commonly identified as fulfilling this retrograde transmitter role is nitric oxide, which, due to its high solubility and diffusivity, often exerts effects on nearby neurons. This type of diffuse synaptic modification, known as volume learning, is not included in the traditional Hebbian model.
== Hebbian learning account of mirror neurons ==
Hebbian learning and spike-timing-dependent plasticity have been used in an influential theory of how mirror neurons emerge. Mirror neurons are neurons that fire both when an individual performs an action and when the individual sees or hears another perform a similar action. The discovery of these neurons has been very influential in explaining how individuals make sense of the actions of others, by showing that, when a person perceives the actions of others, the person activates the motor programs which they would use to perform similar actions. The activation of these motor programs then adds information to the perception and helps predict what the person will do next based on the perceiver's own motor program. A challenge has been to explain how individuals come to have neurons that respond both while performing an action and while hearing or seeing another perform similar actions.
Christian Keysers and David Perrett suggested that as an individual performs a particular action, the individual will see, hear, and feel the performing of the action. These re-afferent sensory signals will trigger activity in neurons responding to the sight, sound, and feel of the action. Because the activity of these sensory neurons will consistently overlap in time with those of the motor neurons that caused the action, Hebbian learning predicts that the synapses connecting neurons responding to the sight, sound, and feel of an action and those of the neurons triggering the action should be potentiated. The same is true while people look at themselves in the mirror, hear themselves babble, or are imitated by others. After repeated experience of this re-afference, the synapses connecting the sensory and motor representations of an action are so strong that the motor neurons start firing to the sound or the vision of the action, and a mirror neuron is created.
Evidence for that perspective comes from many experiments that show that motor programs can be triggered by novel auditory or visual stimuli after repeated pairing of the stimulus with the execution of the motor program (for a review of the evidence, see Giudice et al., 2009). For instance, people who have never played the piano do not activate brain regions involved in playing the piano when listening to piano music. Five hours of piano lessons, in which the participant is exposed to the sound of the piano each time they press a key is proven sufficient to trigger activity in motor regions of the brain upon listening to piano music when heard at a later time. Consistent with the fact that spike-timing-dependent plasticity occurs only if the presynaptic neuron's firing predicts the post-synaptic neuron's firing, the link between sensory stimuli and motor programs also only seem to be potentiated if the stimulus is contingent on the motor program.
== See also ==
== References ==
== Further reading ==
Hebb, D.O. (1961). "Distinctive features of learning in the higher animal". In J. F. Delafresnaye (ed.). Brain Mechanisms and Learning. London: Oxford University Press.
Hebb, D. O. (1940). "Human Behavior After Extensive Bilateral Removal from the Frontal Lobes". Archives of Neurology and Psychiatry. 44 (2): 421–438. doi:10.1001/archneurpsyc.1940.02280080181011.
Bishop, C.M. (1995). Neural Networks for Pattern Recognition. Oxford: Oxford University Press. ISBN 978-0-19-853849-3.
Paulsen, O.; Sejnowski, T. J. (2000). "Natural patterns of activity and long-term synaptic plasticity". Current Opinion in Neurobiology. 10 (2): 172–179. doi:10.1016/S0959-4388(00)00076-3. PMC 2900254. PMID 10753798.
== External links ==
Overview Archived 2017-05-02 at the Wayback Machine
Hebbian Learning tutorial (Part 1: Novelty Filtering, Part 2: PCA) | Hebbian theory is a neuropsychological theory claiming that an increase in synaptic efficacy arises from a presynaptic cell's repeated and persistent stimulation of a postsynaptic cell. It is an attempt to explain synaptic plasticity, the adaptation of brain neurons during the learning process. It was introduced by Donald Hebb in his 1949 book The Organization of Behavior. The theory is also called Hebb's rule, Hebb's postulate, and cell assembly theory. Hebb states it as follows:
Let us assume that the persistence or repetition of a reverberatory activity (or "trace") tends to induce lasting cellular changes that add to its stability. ... When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased.
The theory is often summarized as "Neurons that fire together, wire together." However, Hebb emphasized that cell A needs to "take part in firing" cell B, and such causality can occur only if cell A fires just before, not at the same time as, cell B. This aspect of causation in Hebb's work foreshadowed what is now known about spike-timing-dependent plasticity, which requires temporal precedence.
The theory attempts to explain associative or Hebbian learning, in which simultaneous activation of cells leads to pronounced increases in synaptic strength between those cells. It also provides a biological basis for errorless learning methods for education and memory rehabilitation. In the study of neural networks in cognitive function, it is often regarded as the neuronal basis of unsupervised learning. | 12 |
329 | diarrhea | Durchfall (wiktionary) | IPA(key): /ˈdʊʁçˌfal/
Durchfall m (strong, genitive Durchfalles or Durchfalls, plural Durchfälle)
diarrhea
Synonym: Dünnpfiff
Diarrhoe (medical)
Dünnschiss (slightly vulgar)
Flitzkacke (slightly vulgar/humorous)
“Durchfall” in Digitales Wörterbuch der deutschen Sprache
“Durchfall” in Uni Leipzig: Wortschatz-Lexikon
“Durchfall” in Duden online
“Durchfall” in OpenThesaurus.de
Durchfall on the German Wikipedia.Wikipedia de | IPA(key): /ˈdʊʁçˌfal/
Durchfall m (strong, genitive Durchfalles or Durchfalls, plural Durchfälle)
diarrhea
Synonym: Dünnpfiff
Diarrhoe (medical)
Dünnschiss (slightly vulgar)
Flitzkacke (slightly vulgar/humorous)
“Durchfall” in Digitales Wörterbuch der deutschen Sprache
“Durchfall” in Uni Leipzig: Wortschatz-Lexikon
“Durchfall” in Duden online
“Durchfall” in OpenThesaurus.de
Durchfall on the German Wikipedia.Wikipedia de | 10 |
330 | diarrhea | durchfall (wiktionary) | durchfall
singular imperative of durchfallen | durchfall
singular imperative of durchfallen | 1 |
331 | diarrhea | diarrhea (wiktionary) | diarrhoea (British)
diarrhœa (archaic)
From Middle English diaria, from Middle French diarrie (French diarrhée), from Late Latin diarrhoea, from Ancient Greek διάρροια (diárrhoia, “through-flowing”), from διά (diá, “through”) + ῥέω (rhéō, “flow”). By surface analysis, dia- + -rrhea. Spelling later altered to resemble the word's Latin and Greek roots.
Displaced native Old English ūtsiht (literally “straining out”).
(UK) IPA(key): /ˌdaɪ.əˈɹiː.ə/
Rhymes: -iːə
diarrhea (countable and uncountable, plural diarrheas) (American spelling, Canadian spelling)
A gastrointestinal disorder characterized by frequent and very soft or watery bowel movements.
The watery or very soft excrement that comes from such bowel movements.
2008, Danna Korn and Connie Sarros, Gluten-Free Cooking for Dummies, Chapter 1:
My Pampers bill is higher than your paycheck, my hands are raw from washing them every six minutes, and I do eight loads of laundry a day because everything we own is covered in diarrhea, and you want me to "plug him up" and wait another three weeks?
Diarrhea is the American spelling; diarrhoea is the British spelling.
(medical condition): the runs, the shits, the squirts (US), the trots, the squits (both UK), the skitters (Scottish and Northern English) (all slang)
See also Thesaurus:diarrhea, bubble guts
Montezuma's revenge (informal)
Pharaoh's revenge (informal)
galactorrhea/galactorrhoea
gonorrhea/gonorrhoea
logorrhea/logorrhoea
pyorrhea/pyorrhoea
rheology
diarrheal
diarrheic
antidiarrheal
constipation
piss out one's ass | diarrhoea (British)
diarrhœa (archaic)
From Middle English diaria, from Middle French diarrie (French diarrhée), from Late Latin diarrhoea, from Ancient Greek διάρροια (diárrhoia, “through-flowing”), from διά (diá, “through”) + ῥέω (rhéō, “flow”). By surface analysis, dia- + -rrhea. Spelling later altered to resemble the word's Latin and Greek roots.
Displaced native Old English ūtsiht (literally “straining out”).
(UK) IPA(key): /ˌdaɪ.əˈɹiː.ə/
Rhymes: -iːə
diarrhea (countable and uncountable, plural diarrheas) (American spelling, Canadian spelling)
A gastrointestinal disorder characterized by frequent and very soft or watery bowel movements.
The watery or very soft excrement that comes from such bowel movements.
2008, Danna Korn and Connie Sarros, Gluten-Free Cooking for Dummies, Chapter 1:
My Pampers bill is higher than your paycheck, my hands are raw from washing them every six minutes, and I do eight loads of laundry a day because everything we own is covered in diarrhea, and you want me to "plug him up" and wait another three weeks?
Diarrhea is the American spelling; diarrhoea is the British spelling.
(medical condition): the runs, the shits, the squirts (US), the trots, the squits (both UK), the skitters (Scottish and Northern English) (all slang)
See also Thesaurus:diarrhea, bubble guts
Montezuma's revenge (informal)
Pharaoh's revenge (informal)
galactorrhea/galactorrhoea
gonorrhea/gonorrhoea
logorrhea/logorrhoea
pyorrhea/pyorrhoea
rheology
diarrheal
diarrheic
antidiarrheal
constipation
piss out one's ass | 15 |
332 | diarrhea | Diarrhea (wikipedia) | Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behaviour. This can progress to decreased urination, loss of skin color, a fast heart rate, and a decrease in responsiveness as it becomes more severe. Loose but non-watery stools in babies who are exclusively breastfed, however, are normal.
The most common cause is an infection of the intestines due to a virus, bacterium, or parasite—a condition also known as gastroenteritis. These infections are often acquired from food or water that has been contaminated by feces, or directly from another person who is infected. The three types of diarrhea are: short duration watery diarrhea, short duration bloody diarrhea, and persistent diarrhea (lasting more than two weeks, which can be either watery or bloody). The short duration watery diarrhea may be due to cholera, although this is rare in the developed world. If blood is present, it is also known as dysentery. A number of non-infectious causes can result in diarrhea. These include lactose intolerance, irritable bowel syndrome, non-celiac gluten sensitivity, celiac disease, inflammatory bowel disease such as ulcerative colitis, hyperthyroidism, bile acid diarrhea, and a number of medications. In most cases, stool cultures to confirm the exact cause are not required.
Diarrhea can be prevented by improved sanitation, clean drinking water, and hand washing with soap. Breastfeeding for at least six months and vaccination against rotavirus is also recommended. Oral rehydration solution (ORS)—clean water with modest amounts of salts and sugar—is the treatment of choice. Zinc tablets are also recommended. These treatments have been estimated to have saved 50 million children in the past 25 years. When people have diarrhea it is recommended that they continue to eat healthy food, and babies continue to be breastfed. If commercial ORS is not available, homemade solutions may be used. In those with severe dehydration, intravenous fluids may be required. Most cases, however, can be managed well with fluids by mouth. Antibiotics, while rarely used, may be recommended in a few cases such as those who have bloody diarrhea and a high fever, those with severe diarrhea following travelling, and those who grow specific bacteria or parasites in their stool. Loperamide may help decrease the number of bowel movements but is not recommended in those with severe disease.
About 1.7 to 5 billion cases of diarrhea occur per year. It is most common in developing countries, where young children get diarrhea on average three times a year. Total deaths from diarrhea are estimated at 1.53 million in 2019—down from 2.9 million in 1990. In 2012, it was the second most common cause of deaths in children younger than five (0.76 million or 11%). Frequent episodes of diarrhea are also a common cause of malnutrition and the most common cause in those younger than five years of age. Other long term problems that can result include stunted growth and poor intellectual development.
== Terminology ==
The word diarrhea is from the Ancient Greek διάρροια from διά dia "through" and ῥέω rheo "flow".
Diarrhea is the spelling in American English, whereas diarrhoea is the spelling in British English.
Slang terms for the condition include "the runs", "the squirts" (or "squits" in Britain) and "the trots".
The word is often pronounced as DY-ə-REE-ə.
== Definition ==
Diarrhea is defined by the World Health Organization as having three or more loose or liquid stools per day, or as having more stools than is normal for that person.
Acute diarrhea is defined as an abnormally frequent discharge of semisolid or fluid fecal matter from the bowel, lasting less than 14 days, by World Gastroenterology Organization. Acute diarrhea that is watery may be known as AWD (Acute Watery Diarrhoea.)
=== Secretory ===
Secretory diarrhea means that there is an increase in the active secretion, or there is an inhibition of absorption. There is little to no structural damage. The most common cause of this type of diarrhea is a cholera toxin that stimulates the secretion of anions, especially chloride ions (Cl–). Therefore, to maintain a charge balance in the gastrointestinal tract, sodium (Na+) is carried with it, along with water. In this type of diarrhea intestinal fluid secretion is isotonic with plasma even during fasting. It continues even when there is no oral food intake.
=== Osmotic ===
Osmotic diarrhea occurs when too much water is drawn into the bowels. If a person drinks solutions with excessive sugar or excessive salt, these can draw water from the body into the bowel and cause osmotic diarrhea. Osmotic diarrhea can also result from maldigestion, e.g. pancreatic disease or coeliac disease, in which the nutrients are left in the lumen to pull in water. Or it can be caused by osmotic laxatives (which work to alleviate constipation by drawing water into the bowels). In healthy individuals, too much magnesium or vitamin C or undigested lactose can produce osmotic diarrhea and distention of the bowel. A person who has lactose intolerance can have difficulty absorbing lactose after an extraordinarily high intake of dairy products. In persons who have fructose malabsorption, excess fructose intake can also cause diarrhea. High-fructose foods that also have a high glucose content are more absorbable and less likely to cause diarrhea. Sugar alcohols such as sorbitol (often found in sugar-free foods) are difficult for the body to absorb and, in large amounts, may lead to osmotic diarrhea. In most of these cases, osmotic diarrhea stops when the offending agent, e.g. milk or sorbitol, is stopped.
=== Exudative ===
Exudative diarrhea occurs with the presence of blood and pus in the stool. This occurs with inflammatory bowel diseases, such as Crohn's disease or ulcerative colitis, and other severe infections such as E. coli or other forms of food poisoning.
=== Inflammatory ===
Inflammatory diarrhea occurs when there is damage to the mucosal lining or brush border, which leads to a passive loss of protein-rich fluids and a decreased ability to absorb these lost fluids. Features of all three of the other types of diarrhea can be found in this type of diarrhea. It can be caused by bacterial infections, viral infections, parasitic infections, or autoimmune problems such as inflammatory bowel diseases. It can also be caused by tuberculosis, colon cancer, and enteritis.
=== Dysentery ===
If there is blood visible in the stools, it is also known as dysentery. The blood is a trace of an invasion of bowel tissue. Dysentery is a symptom of, among others, Shigella, Entamoeba histolytica, and Salmonella.
== Health effects ==
Diarrheal disease may have a negative impact on both physical fitness and mental development. "Early childhood malnutrition resulting from any cause reduces physical fitness and work productivity in adults," and diarrhea is a primary cause of childhood malnutrition. Further, evidence suggests that diarrheal disease has significant impacts on mental development and health; it has been shown that, even when controlling for helminth infection and early breastfeeding, children who had experienced severe diarrhea had significantly lower scores on a series of tests of intelligence.
Diarrhea can cause electrolyte imbalances, kidney impairment, dehydration, and defective immune system responses. When oral drugs are administered, the efficiency of the drug is to produce a therapeutic effect and the lack of this effect may be due to the medication travelling too quickly through the digestive system, limiting the time that it can be absorbed. Clinicians try to treat the diarrheas by reducing the dosage of medication, changing the dosing schedule, discontinuation of the drug, and rehydration. The interventions to control the diarrhea are not often effective. Diarrhea can have a profound effect on the quality of life because fecal incontinence is one of the leading factors for placing older adults in long term care facilities (nursing homes).
== Causes ==
In the latter stages of human digestion, ingested materials are inundated with water and digestive fluids such as gastric acid, bile, and digestive enzymes in order to break them down into their nutrient components, which are then absorbed into the bloodstream via the intestinal tract in the small intestine. Prior to defecation, the large intestine reabsorbs the water and other digestive solvents in the waste product in order to maintain proper hydration and overall equilibrium. Diarrhea occurs when the large intestine is prevented, for any number of reasons, from sufficiently absorbing the water or other digestive fluids from fecal matter, resulting in a liquid, or "loose", bowel movement.
Acute diarrhea is most commonly due to viral gastroenteritis with rotavirus, which accounts for 40% of cases in children under five. In travelers, however, bacterial infections predominate. Various toxins such as mushroom poisoning and drugs can also cause acute diarrhea.
Chronic diarrhea can be the part of the presentations of a number of chronic medical conditions affecting the intestine. Common causes include ulcerative colitis, Crohn's disease, microscopic colitis, celiac disease, irritable bowel syndrome, and bile acid malabsorption.
=== Infections ===
There are many causes of infectious diarrhea, which include viruses, bacteria and parasites. Infectious diarrhea is frequently referred to as gastroenteritis. Norovirus is the most common cause of viral diarrhea in adults, but rotavirus is the most common cause in children under five years old. Adenovirus types 40 and 41, and astroviruses cause a significant number of infections. Shiga-toxin producing Escherichia coli, such as E coli o157:h7, are the most common cause of infectious bloody diarrhea in the United States.
Campylobacter spp. are a common cause of bacterial diarrhea, but infections by Salmonella spp., Shigella spp. and some strains of Escherichia coli are also a frequent cause.
In the elderly, particularly those who have been treated with antibiotics for unrelated infections, a toxin produced by Clostridioides difficile often causes severe diarrhea.
Parasites, particularly protozoa e.g., Cryptosporidium spp., Giardia spp., Entamoeba histolytica, Blastocystis spp., Cyclospora cayetanensis, are frequently the cause of diarrhea that involves chronic infection. The broad-spectrum antiparasitic agent nitazoxanide has shown efficacy against many diarrhea-causing parasites.
Other infectious agents, such as parasites or bacterial toxins, may exacerbate symptoms. In sanitary living conditions where there is ample food and a supply of clean water, an otherwise healthy person usually recovers from viral infections in a few days. However, for ill or malnourished individuals, diarrhea can lead to severe dehydration and can become life-threatening.
==== Sanitation ====
Open defecation is a leading cause of infectious diarrhea leading to death.
Poverty is a good indicator of the rate of infectious diarrhea in a population. This association does not stem from poverty itself, but rather from the conditions under which impoverished people live. The absence of certain resources compromises the ability of the poor to defend themselves against infectious diarrhea. "Poverty is associated with poor housing, crowding, dirt floors, lack of access to clean water or to sanitary disposal of fecal waste (sanitation), cohabitation with domestic animals that may carry human pathogens, and a lack of refrigerated storage for food, all of which increase the frequency of diarrhea ... Poverty also restricts the ability to provide age-appropriate, nutritionally balanced diets or to modify diets when diarrhea develops so as to mitigate and repair nutrient losses. The impact is exacerbated by the lack of adequate, available, and affordable medical care."
One of the most common causes of infectious diarrhea is a lack of clean water. Often, improper fecal disposal leads to contamination of groundwater. This can lead to widespread infection among a population, especially in the absence of water filtration or purification. Human feces contains a variety of potentially harmful human pathogens.
==== Nutrition ====
Proper nutrition is important for health and functioning, including the prevention of infectious diarrhea. It is especially important to young children who do not have a fully developed immune system. Zinc deficiency, a condition often found in children in developing countries can, even in mild cases, have a significant impact on the development and proper functioning of the human immune system. Indeed, this relationship between zinc deficiency and reduced immune functioning corresponds with an increased severity of infectious diarrhea. Children who have lowered levels of zinc have a greater number of instances of diarrhea, severe diarrhea, and diarrhea associated with fever. Similarly, vitamin A deficiency can cause an increase in the severity of diarrheal episodes. However, there is some discrepancy when it comes to the impact of vitamin A deficiency on the rate of disease. While some argue that a relationship does not exist between the rate of disease and vitamin A status, others suggest an increase in the rate associated with deficiency. Given that estimates suggest 127 million preschool children worldwide are vitamin A deficient, this population has the potential for increased risk of disease contraction.
=== Malabsorption ===
Malabsorption is the inability to absorb food fully, mostly from disorders in the small bowel, but also due to maldigestion from diseases of the pancreas.
Causes include:
enzyme deficiencies or mucosal abnormality, as in food allergy and food intolerance, e.g. celiac disease (gluten intolerance), lactose intolerance (intolerance to milk sugar, common in non-Europeans), and fructose malabsorption.
pernicious anemia, or impaired bowel function due to the inability to absorb vitamin B12,
loss of pancreatic secretions, which may be due to cystic fibrosis or pancreatitis,
structural defects, like short bowel syndrome (surgically removed bowel) and radiation fibrosis, such as usually follows cancer treatment and other drugs, including agents used in chemotherapy; and
certain drugs, like orlistat, which inhibits the absorption of fat.
=== Inflammatory bowel disease ===
The two overlapping types here are of unknown origin:
Ulcerative colitis is marked by chronic bloody diarrhea and inflammation mostly affects the distal colon near the rectum.
Crohn's disease typically affects fairly well demarcated segments of bowel in the colon and often affects the end of the small bowel.
=== Irritable bowel syndrome ===
Another possible cause of diarrhea is irritable bowel syndrome (IBS), which usually presents with abdominal discomfort relieved by defecation and unusual stool (diarrhea or constipation) for at least three days a week over the previous three months. Symptoms of diarrhea-predominant IBS can be managed through a combination of dietary changes, soluble fiber supplements and medications such as loperamide or codeine. About 30% of patients with diarrhea-predominant IBS have bile acid malabsorption diagnosed with an abnormal SeHCAT test.
=== Other diseases ===
Diarrhea can be caused by other diseases and conditions, namely:
Chronic ethanol ingestion
Hyperthyroidism
Certain medications
Bile acid malabsorption
Ischemic bowel disease: This usually affects older people and can be due to blocked arteries.
Microscopic colitis, a type of inflammatory bowel disease where changes are seen only on histological examination of colonic biopsies.
Bile salt malabsorption (primary bile acid diarrhea) where excessive bile acids in the colon produce a secretory diarrhea.
Hormone-secreting tumors: some hormones, e.g. serotonin, can cause diarrhea if secreted in excess (usually from a tumor).
Chronic mild diarrhea in infants and toddlers may occur with no obvious cause and with no other ill effects; this condition is called toddler's diarrhea.
Environmental enteropathy
Radiation enteropathy following treatment for pelvic and abdominal cancers.
=== Medications ===
Over 700 medications, such as penicillin, are known to cause diarrhea. The classes of medications that are known to cause diarrhea are laxatives, antacids, heartburn medications, antibiotics, anti-neoplastic drugs, anti-inflammatories as well as many dietary supplements.
== Pathophysiology ==
=== Evolution ===
According to two researchers, Nesse and Williams, diarrhea may function as an evolved expulsion defense mechanism. As a result, if it is stopped, there might be a delay in recovery. They cite in support of this argument research published in 1973 that found that treating Shigella with the anti-diarrhea drug (Co-phenotrope, Lomotil) caused people to stay feverish twice as long as those not so treated. The researchers indeed themselves observed that: "Lomotil may be contraindicated in shigellosis. Diarrhea may represent a defense mechanism".
== Diagnostic approach ==
The following types of diarrhea may indicate further investigation is needed:
In infants
Moderate or severe diarrhea in young children
Associated with blood
Continues for more than two days
Associated non-cramping abdominal pain, fever, weight loss, etc.
In travelers
In food handlers, because of the potential to infect others;
In institutions such as hospitals, child care centers, or geriatric and convalescent homes.
A severity score is used to aid diagnosis in children.
When diarrhea lasts for more than four weeks a number of further tests may be recommended including:
Complete blood count and a ferritin if anemia is present
Thyroid stimulating hormone
Tissue transglutaminase for celiac disease
Fecal calprotectin to exclude inflammatory bowel disease
Stool tests for ova and parasites as well as for Clostridioides difficile
A colonoscopy or fecal immunochemical testing for cancer, including biopsies to detect microscopic colitis
Testing for bile acid diarrhea with SeHCAT, 7α-hydroxy-4-cholesten-3-one or fecal bile acids depending on availability
Hydrogen breath test looking for lactose intolerance
Further tests if immunodeficiency, pelvic radiation disease or small intestinal bacterial overgrowth suspected.
A 2019 guideline recommended that testing for ova and parasites was only needed in people who are at high risk though they recommend routine testing for giardia. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were not recommended.
== Epidemiology ==
Worldwide in 2004, approximately 2.5 billion cases of diarrhea occurred, which resulted in 1.5 million deaths among children under the age of five. Greater than half of these were in Africa and South Asia. This is down from a death rate of 4.5 million in 1980 for gastroenteritis. Diarrhea remains the second leading cause of infant mortality (16%) after pneumonia (17%) in this age group.
The majority of such cases occur in the developing world, with over half of the recorded cases of childhood diarrhea occurring in Africa and Asia, with 696 million and 1.2 billion cases, respectively, compared to only 480 million in the rest of the world.
Infectious diarrhea resulted in about 0.7 million deaths in children under five years old in 2011 and 250 million lost school days. In the Americas, diarrheal disease accounts for a total of 10% of deaths among children aged 1–59 months while in South East Asia, it accounts for 31.3% of deaths. It is estimated that around 21% of child mortalities in developing countries are due to diarrheal disease.
Even though diarrhea is best known in humans, it affects many other species, notably among primates. The cecal appendix, when present, appears to afford some protection against diarrhea to young primates.
== Prevention ==
=== Sanitation ===
Numerous studies have shown that improvements in drinking water and sanitation (WASH) lead to decreased risks of diarrhoea. Such improvements might include for example use of water filters, provision of high-quality piped water and sewer connections.
In institutions, communities, and households, interventions that promote hand washing with soap lead to significant reductions in the incidence of diarrhea. The same applies to preventing open defecation at a community-wide level and providing access to improved sanitation. This includes use of toilets and implementation of the entire sanitation chain connected to the toilets (collection, transport, disposal or reuse of human excreta).
There is limited evidence that safe disposal of child or adult feces can prevent diarrheal disease.
==== Hand washing ====
Basic sanitation techniques can have a profound effect on the transmission of diarrheal disease. The implementation of hand washing using soap and water, for example, has been experimentally shown to reduce the incidence of disease by approximately 30–48%. Hand washing in developing countries, however, is compromised by poverty as acknowledged by the CDC: "Handwashing is integral to disease prevention in all parts of the world; however, access to soap and water is limited in a number of less developed countries. This lack of access is one of many challenges to proper hygiene in less developed countries." Solutions to this barrier require the implementation of educational programs that encourage sanitary behaviours.
==== Water ====
Given that water contamination is a major means of transmitting diarrheal disease, efforts to provide clean water supply and improved sanitation have the potential to dramatically cut the rate of disease incidence. In fact, it has been proposed that we might expect an 88% reduction in child mortality resulting from diarrheal disease as a result of improved water sanitation and hygiene. Similarly, a meta-analysis of numerous studies on improving water supply and sanitation shows a 22–27% reduction in disease incidence, and a 21–30% reduction in mortality rate associated with diarrheal disease.
Chlorine treatment of water, for example, has been shown to reduce both the risk of diarrheal disease, and of contamination of stored water with diarrheal pathogens.
=== Vaccination ===
Immunization against the pathogens that cause diarrheal disease is a viable prevention strategy, however it does require targeting certain pathogens for vaccination. In the case of Rotavirus, which was responsible for around 6% of diarrheal episodes and 20% of diarrheal disease deaths in the children of developing countries, use of a Rotavirus vaccine in trials in 1985 yielded a slight (2–3%) decrease in total diarrheal disease incidence, while reducing overall mortality by 6–10%. Similarly, a Cholera vaccine showed a strong reduction in morbidity and mortality, though the overall impact of vaccination was minimal as Cholera is not one of the major causative pathogens of diarrheal disease. Since this time, more effective vaccines have been developed that have the potential to save many thousands of lives in developing nations, while reducing the overall cost of treatment, and the costs to society.
Rotavirus vaccine decreases the rates of diarrhea in a population. New vaccines against rotavirus, Shigella, Enterotoxigenic Escherichia coli (ETEC), and cholera are under development, as well as other causes of infectious diarrhea.
=== Nutrition ===
Dietary deficiencies in developing countries can be combated by promoting better eating practices. Zinc supplementation proved successful showing a significant decrease in the incidence of diarrheal disease compared to a control group. The majority of the literature suggests that vitamin A supplementation is advantageous in reducing disease incidence. Development of a supplementation strategy should take into consideration the fact that vitamin A supplementation was less effective in reducing diarrhea incidence when compared to vitamin A and zinc supplementation, and that the latter strategy was estimated to be significantly more cost effective.
==== Breastfeeding ====
Breastfeeding practices have been shown to have a dramatic effect on the incidence of diarrheal disease in poor populations. Studies across a number of developing nations have shown that those who receive exclusive breastfeeding during their first 6 months of life are better protected against infection with diarrheal diseases. One study in Brazil found that non-breastfed infants were 14 times more likely to die from diarrhea than exclusively breastfed infants. Exclusive breastfeeding is currently recommended for the first six months of an infant's life by the WHO, with continued breastfeeding until at least two years of age.
=== Others ===
Probiotics decrease the risk of diarrhea in those taking antibiotics. Insecticide spraying may reduce fly numbers and the risk of diarrhea in children in a setting where there is seasonal variations in fly numbers throughout the year.
== Management ==
In many cases of diarrhea, replacing lost fluid and salts is the only treatment needed. This is usually by mouth – oral rehydration therapy – or, in severe cases, intravenously. Diet restrictions such as the BRAT diet are no longer recommended. Research does not support the limiting of milk to children as doing so has no effect on duration of diarrhea. To the contrary, WHO recommends that children with diarrhea continue to eat as sufficient nutrients are usually still absorbed to support continued growth and weight gain, and that continuing to eat also speeds up recovery of normal intestinal functioning. CDC recommends that children and adults with cholera also continue to eat. There is no evidence that early refeeding in children can cause an increase in inappropriate use of intravenous fluid, episodes of vomiting, and risk of having persistent diarrhea.
Medications such as loperamide (Imodium) and bismuth subsalicylate may be beneficial; however they may be contraindicated in certain situations.
=== Fluids ===
Oral rehydration solution (ORS) (a slightly sweetened and salty water) can be used to prevent dehydration. Standard home solutions such as salted rice water, salted yogurt drinks, vegetable and chicken soups with salt can be given. Home solutions such as water in which cereal has been cooked, unsalted soup, green coconut water, weak tea (unsweetened), and unsweetened fresh fruit juices can have from half a teaspoon to full teaspoon of salt (from one-and-a-half to three grams) added per liter. Clean plain water can also be one of several fluids given. There are commercial solutions such as Pedialyte, and relief agencies such as UNICEF widely distribute packets of salts and sugar. A WHO publication for physicians recommends a homemade ORS consisting of one liter water with one teaspoon salt (3 grams) and two tablespoons sugar (18 grams) added (approximately the "taste of tears"). Rehydration Project recommends adding the same amount of sugar but only one-half a teaspoon of salt, stating that this more dilute approach is less risky with very little loss of effectiveness. Both agree that drinks with too much sugar or salt can make dehydration worse.
Appropriate amounts of supplemental zinc and potassium should be added if available. But the availability of these should not delay rehydration. As WHO points out, the most important thing is to begin preventing dehydration as early as possible. In another example of prompt ORS hopefully preventing dehydration, CDC recommends for the treatment of cholera continuing to give Oral Rehydration Solution during travel to medical treatment.
Vomiting often occurs during the first hour or two of treatment with ORS, especially if a child drinks the solution too quickly, but this seldom prevents successful rehydration since most of the fluid is still absorbed. WHO recommends that if a child vomits, to wait five or ten minutes and then start to give the solution again more slowly.
Drinks especially high in simple sugars, such as soft drinks and fruit juices, are not recommended in children under five as they may increase dehydration. A too rich solution in the gut draws water from the rest of the body, just as if the person were to drink sea water. Plain water may be used if more specific and effective ORT preparations are unavailable or are not palatable. Additionally, a mix of both plain water and drinks perhaps too rich in sugar and salt can alternatively be given to the same person, with the goal of providing a medium amount of sodium overall. A nasogastric tube can be used in young children to administer fluids if warranted.
=== Eating ===
The WHO recommends a child with diarrhea continue to be fed. Continued feeding speeds the recovery of normal intestinal function. In contrast, children whose food is restricted have diarrhea of longer duration and recover intestinal function more slowly. The WHO states "Food should never be withheld and the child's usual foods should not be diluted. Breastfeeding should always be continued." In the specific example of cholera, the CDC makes the same recommendation. Breast-fed infants with diarrhea often choose to breastfeed more, and should be encouraged to do so. In young children who are not breast-fed and live in the developed world, a lactose-free diet may be useful to speed recovery.
Eating food containing soluble fibre may help, but insoluble fibre might make it worse.
=== Medications ===
Antidiarrheal agents can be classified into four different groups: antimotility, antisecretory, adsorbent, and anti-infectious. While antibiotics are beneficial in certain types of acute diarrhea, they are usually not used except in specific situations. There are concerns that antibiotics may increase the risk of hemolytic uremic syndrome in people infected with Escherichia coli O157:H7. In resource-poor countries, treatment with antibiotics may be beneficial. However, some bacteria are developing antibiotic resistance, particularly Shigella. Antibiotics can also cause diarrhea, and antibiotic-associated diarrhea is the most common adverse effect of treatment with general antibiotics.
While bismuth compounds (Pepto-Bismol) decreased the number of bowel movements in those with travelers' diarrhea, they do not decrease the length of illness. Anti-motility agents like loperamide are also effective at reducing the number of stools but not the duration of disease. These agents should be used only if bloody diarrhea is not present.
Diosmectite, a natural aluminomagnesium silicate clay, is effective in alleviating symptoms of acute diarrhea in children, and also has some effects in chronic functional diarrhea, radiation-induced diarrhea, and chemotherapy-induced diarrhea. Another absorbent agent used for the treatment of mild diarrhea is kaopectate.
Racecadotril an antisecretory medication may be used to treat diarrhea in children and adults. It has better tolerability than loperamide, as it causes less constipation and flatulence. However, it has little benefit in improving acute diarrhea in children.
Bile acid sequestrants such as cholestyramine can be effective in chronic diarrhea due to bile acid malabsorption. Therapeutic trials of these drugs are indicated in chronic diarrhea if bile acid malabsorption cannot be diagnosed with a specific test, such as SeHCAT retention.
=== Alternative therapies ===
Zinc supplementation may benefit children over six months old with diarrhea in areas with high rates of malnourishment or zinc deficiency. This supports the World Health Organization guidelines for zinc, but not in the very young.
A Cochrane Review from 2020 concludes that probiotics make little or no difference to people who have diarrhea lasting 2 days or longer and that there is no proof that they reduce its duration. The probiotic lactobacillus can help prevent antibiotic-associated diarrhea in adults but possibly not children. For those with lactose intolerance, taking digestive enzymes containing lactase when consuming dairy products often improves symptoms.
== See also ==
Dysentery – Inflammation of the intestine causing diarrhea with blood
Fernando Mazariegos – Guatemalan scientist (1938–2018)
== References ==
== External links ==
WHO fact sheet on diarrhoeal disease | Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behaviour. This can progress to decreased urination, loss of skin color, a fast heart rate, and a decrease in responsiveness as it becomes more severe. Loose but non-watery stools in babies who are exclusively breastfed, however, are normal.
The most common cause is an infection of the intestines due to a virus, bacterium, or parasite—a condition also known as gastroenteritis. These infections are often acquired from food or water that has been contaminated by feces, or directly from another person who is infected. The three types of diarrhea are: short duration watery diarrhea, short duration bloody diarrhea, and persistent diarrhea (lasting more than two weeks, which can be either watery or bloody). The short duration watery diarrhea may be due to cholera, although this is rare in the developed world. If blood is present, it is also known as dysentery. A number of non-infectious causes can result in diarrhea. These include lactose intolerance, irritable bowel syndrome, non-celiac gluten sensitivity, celiac disease, inflammatory bowel disease such as ulcerative colitis, hyperthyroidism, bile acid diarrhea, and a number of medications. In most cases, stool cultures to confirm the exact cause are not required.
Diarrhea can be prevented by improved sanitation, clean drinking water, and hand washing with soap. Breastfeeding for at least six months and vaccination against rotavirus is also recommended. Oral rehydration solution (ORS)—clean water with modest amounts of salts and sugar—is the treatment of choice. Zinc tablets are also recommended. These treatments have been estimated to have saved 50 million children in the past 25 years. When people have diarrhea it is recommended that they continue to eat healthy food, and babies continue to be breastfed. If commercial ORS is not available, homemade solutions may be used. In those with severe dehydration, intravenous fluids may be required. Most cases, however, can be managed well with fluids by mouth. Antibiotics, while rarely used, may be recommended in a few cases such as those who have bloody diarrhea and a high fever, those with severe diarrhea following travelling, and those who grow specific bacteria or parasites in their stool. Loperamide may help decrease the number of bowel movements but is not recommended in those with severe disease.
About 1.7 to 5 billion cases of diarrhea occur per year. It is most common in developing countries, where young children get diarrhea on average three times a year. Total deaths from diarrhea are estimated at 1.53 million in 2019—down from 2.9 million in 1990. In 2012, it was the second most common cause of deaths in children younger than five (0.76 million or 11%). Frequent episodes of diarrhea are also a common cause of malnutrition and the most common cause in those younger than five years of age. Other long term problems that can result include stunted growth and poor intellectual development. | 29 |
333 | diarrhea | Diarrhea (disambiguation) (wikipedia) | Diarrhea or diarrhoea is liquid defecation.
Diarrhea may also refer to:
== Music ==
Diarrhea Planet, a garage punk band (formed 2009)
Live Fast, Diarrhea, a 1995 album by The Vandals
Diarrhea of a Madman, a 2001 album by Dave Brockie Experience
"Diarrhea", a song by Da Yoopers on the 1989 album Yoop It Up
== Television ==
Daria Morgendorffer, a Beavis and Butthead character (nickname: Diarrhea)
== See also ==
‹The template Category link is being considered for merging.› Category:Diarrhea ( 28 )
Defecation
Shit, a word originally referring to diarrhea | Diarrhea or diarrhoea is liquid defecation.
Diarrhea may also refer to: | 1 |
334 | diarrhea | Daria Morgendorffer (wikipedia) | Daria Morgendorffer is a fictional character and the enponymous main protagonist of the MTV adult animated series Daria, which originally aired from March 1997 to January 2002. She was initially designed and created by Beavis and Butt-Head staff writer David Felton as a supporting character, serving as an intelligent foil to the two main characters. Eventually, MTV sought to make an animated show catered more to female viewers, and thus Glenn Eichler and Susie Lewis Lynn co-developed Daria. She was voiced in both productions by Tracy Grandstaff.
In 2002, Daria placed at number 41 on the list of the Top 50 Greatest Cartoon Characters of All Time by TV Guide for her role in the two shows. She was also listed in AOL's 100 Most Memorable Female TV Characters.
== Conception and development ==
Mike Judge created the Daria character on advice of the network. MTV senior vice president and creative director Abby Terkuhle explained that when Beavis and Butt-Head "became successful, we ... created Daria's character because we wanted a smart female who could serve as the foil." Terkuhle said that he added Daria "to put Beavis and Butt-Head in their place". Judge says that Daria was named for a girl he knew in school who, like the character, was saddled with the nickname "Diarrhea". Glenn Eichler, who created the Daria spin-off – sometimes incorrectly stated to be the character's creator as well – was, along with Peggy Nicoll, one of the main writers of the series; other writers were Neena Beber, Anne D. Bernstein, Rachelle Romberg, Rachel Lipman, and Sam Johnson.
== In Beavis and Butt-Head ==
In Daria's first incarnation as a recurring character on Beavis and Butt-Head, she formed an intelligent female foil to the two main characters. She went through three different outfits, had a stockier figure, and initially was a more expressive character; her iconic monotone voice developed over time. While she later became more sardonic, she showed early on that she could hold her own against the two and could react quickly to their antics.
In her debut episode, "Scientific Stuff", she was forced to do a science class presentation with Beavis and Butt-Head. At first, Daria is horrified by this and voiced out her complaints to Mrs. Dickie against having to work with the pair due to their history of stupidity and lack of common sense. She later turned it to her advantage by using them as the presentation's experiment. She had a minor role in her next two appearances, in "Babes R Us" and "Sign Here". In "Sign Here" she answered questions from David Van Driessen on furriers and their treatment of animals. In later appearances, she alternated between being irritated by their antics and finding their stupidity to be amusing: in "Sprout", she specifically came over to watch them fail at planting seeds, and in "Walkathon" she got them to unwittingly pledge $100 apiece on a charity walkathon. In "Sporting Goods" she gave three eye-popping gasps while Beavis and Butt-Head wear eye patches as athletic supporters, which is a dramatic contrast to her monotonous behavior in the later series. She lacked the passionate hatred for them that Principal McVicker and Coach Buzzcut had and was one of the very few characters that would willingly seek them out, but did not really believe there is any hope for them either, as Van Driessen had. On multiple occasions, she took it upon herself to explain simple concepts to them, such as informing them in "U.S. History" what graduation was (Beavis responded, "You mean, like ... school ends?") and in "Sprout" that you put seeds in the ground.
In a Christmas special, it is stated that Butt-Head had been responsible for giving her a negative outlook on boys. Aside from that, she was one of the few characters that the duo never managed to drive crazy as they had with many other students and teachers. Butt-Head sometimes treated her with some degree of respect, following her advice in "Sprout" and chuckling "Daria's cool!" after she asked Bill Clinton if "you were just jerking us around" on a campaign promise.
John J. O'Connor of The New York Times describes Daria as "as sharp as B. & B. are dimwitted". John Allemang of The Globe and Mail described Daria in Beavis and Butt-Head "the prematurely wise girl who could be counted on to put their idiocy in perspective." Beavis and Butt-Head often call her "Diarrhea".
In the final episode of season 7 (her only appearance in season 7 of Beavis and Butthead; by this time, her own series had been on the air for nearly 9 months), when the boys were believed dead, Daria expressed the sentiments that "I guess it's sad they're dead", but they did not have very bright futures to look forward to.
Daria appeared frequently in the Marvel Comics adaptation of the TV show, and also got to appear on the cover of one issue and "answer" the fan mail in two others. In Beavis and Butt-Head Do America, she appears once throughout the film with a group of students, but does not have any dialogue.
Daria's own show never mentioned Beavis and Butt-Head and named Highland only once at the beginning of the first episode of season one, carried over from the original and unbroadcast pilot. Despite this, it was frequently noted in media articles about the show that it was a spin-off from Beavis and Butt-Head. In an "interview" on CBS Early Show on January 21, 2002, Daria was asked by Jane Clayson if she kept in touch with Beavis and Butt-Head; she responded "I'd like to, but first they'd have to figure out that when the telephone makes that funny sound, you're supposed to pick it up and say hello".
As revealed in a Rolling Stone interview with Mike Judge, Daria would not return to the new episodes of Beavis and Butt-Head in 2011, but she was referenced in "Drones" during a music video when Beavis assumed she had committed suicide. However, Butt-Head incredulously tells his friend "What are you talking about, Beavis? Daria didn't die, she just moved away".
Daria made a brief, silent cameo in the 2022 Paramount+ film Beavis and Butt-Head Do the Universe, during Beavis and Butt-Head's sentencing, upset with the fact that the boys got off scot-free with their crime.
In the 2022–23 season finale episode, "Abduction", Daria plays "Smart Daria", one of the judges who sentences Smart Butt-Head and Smart Beavis back to earth to try to complete a mission or face the death sentence.
== In Daria ==
In the series Daria, which followed Beavis and Butt-Head, Daria remains bespectacled and plain. She is an unfashionably dressed, highly intellectual, entirely pessimistic about life altogether, cynical, and sarcastic teenage girl who is portrayed as an icon of sanity in an insane household in an equally insane upper middle class suburb. She resides with her vacuous, fashion-obsessed younger sister Quinn and career-obsessed parents Helen and Jake. Their family name, "Morgendorffer" (lit. "one from Dawn Village", Morgen + Dorf + -er), indicates that her father's family originally hails from Germanic roots. John Allemang of The Globe and Mail said that Daria is "both the disappointment of her overachieving parents and an embarrassment to her boy-crazy sister Quinn". She had moved to a new school, having transferred from the one in Beavis and Butt-Head. Glenn Eichler said, in relation to Daria the series, of which he was a co-creator, "I like to think that I've helped her come out of her shell."
David L. Coddon of the San Diego Union-Tribune described Daria as "the anti-cheerleader, the un-social climber, the jaundiced eye in a cartoon world of too much makeup and superficial crayon colors". Coddon added that Daria "may look like a misfit, but the catch is that Daria's the only character on the show who 'gets it'. It's everyone else who's a misfit." Daria states in the first episode that she does not have low self-esteem: she has low esteem for everybody else. Anita Gates of The New York Times said "The secret of Daria's popularity (everywhere but in her own home and school) may be our collective alienation." Gates says "her tastes are a little dark." As an example, Gates used the fact that she reads "Howl" by Allen Ginsberg at a reading to the elderly program.
Eichler said, "Apparently everyone, with the exception of a very few people who were hit on the head when they were very young, felt like they were outsiders. You either identify with her as an outsider or you sort of envy her ability to navigate her life as an outsider and stay sane." John J. O'Connor, a television critic for The New York Times, said "In short, Daria is the perfect anti-Barbie Doll. Merchants of fashion and cosmetics are beneath her contempt. Her refusal to be Miss Goody Consumer borders on the truly subversive." He concludes that Daria "is every glorious misfit I ever knew".
Allemang said that in Daria, Daria "seems more tortured and neurotic, if only because it's more clear that the airheads have won". Daria often talks to herself. Allemang adds "in a perky-teen world with its twisted values, soliloquies are the best hope of intelligent conversation." In addition he said "There's nothing intrinsically wrong with Daria, just because she can't or won't hang out with the cool kids." John J. O'Connor of The New York Times said that Daria has "a withering eye" towards her classmates. Emily Nussbaum for Slate would praise the show both for having a character that many disaffected teenagers could relate to and for showing "the flipside of her principled withdrawal from the world: her crippling terror of rejection, a streak of ugly self-righteousness".
Daria likes to watch the fictitious television show Sick, Sad World. Gates added that "Daria is the kind of girl who reads Heart of Darkness and Edgar Allan Poe's 'Telltale Heart' in class."
=== Relationships with other characters ===
Anita Gates of The New York Times says "The Morgendorffers don't even seem to notice that Daria constantly gives them lip." In one scene, when Helen, her mother, says, "There's no course that can teach you to be a perfect mother," Daria responds "That's obvious." Gates says that "nobody sends her to her room". Gates also said that Daria's popular, self-absorbed sister Quinn is "the greatest burden on the home front". Jane Lane, Daria's best friend, met her at a self-esteem class. Gates adds that Jane "knows all of Daria's peculiarities and still loves her". Gates said that Daria's "silent intense crush" on Jane's brother Trent is her "only discernible weakness" and that "the absolute proof that Jane is a good friend is that she knows how Daria feels about Trent and will never, ever tell." In spite of her early infatuation with Trent, Daria's most significant romantic relationship is with Tom Sloane, who entered the show at the end of the third season and rapidly became Jane's love interest before beginning a relationship with Daria that continued throughout the rest of the show and caused some friction between Daria and Jane.
=== Movies ===
The first Daria movie, Is It Fall Yet?, gave the principal characters time apart from one another in parallel narratives which foreshadowed further changes in their relationships.
By the time of the finale movie Is It College Yet?, Daria's character has undergone noticeable growth. She chooses to attend Raft College. She graduates from Lawndale High, winning the Dian Fossey Award "for dazzling academic achievements in face of near total misanthropy", and crowning her acceptance speech with the assertion that "there is no aspect, no facet, no moment of life that can't be improved with pizza."
== Appearance ==
Daria has shoulder-length brown hair and wears glasses with round black frames. Her everyday outfit consists of an orange T-shirt underneath a green jacket, a black skirt, and black boots. John Allemang of The Globe and Mail said "to surrender is to be normal, to sacrifice your brain in the rush to be popular and wear uncomfortable shoes that make your legs look hot. Daria, as always, keeps her integrity. She wears sensible shoes, and finds her intellectual reward in not being hot."
In Beavis and Butt-Head, Daria wears square glasses, a black leather jacket, white T-shirt, a red skirt, black leggings and black boots. In the earlier episodes, she is seen wearing a brown jacket, beige skirt, green shirt and brown boots.
== MTV "host" ==
During her run on MTV, Daria would narrate or "host" special events and shows, either with a real-life presenter or with Jane. She was part of the Cool Crap Auction in 1999, giving an overview of the goods for auction and talking "live" to the winner of one prize, answering machine messages recorded by her. Daria and Jane also hosted MTV's Top Ten Animated Videos Countdown and two Daria Day marathons of their episodes; the Countdown and second marathon segments are included on the 2010 DVD release.
== Cameos ==
Daria makes a brief cameo in the Drawn Together episode "Lost in Parking Space, Part Two". She is being tortured in the basement of a Hot Topic along with other cartoon characters. She has a nail being hammered into her eye and says, "This is men's fault", in her infamous monotone and is rather indifferent to the pain. Also, at one point in the MTV animated series Undergrads, Gimpy is talking to his friends via webcam when a female hacker hacks into the video stream and edits Gimpy to look like Daria.
In late 2010, following the DVD release, Daria was licensed as a voice for Garmin and TomTom GPS systems; original putdowns and jokes were recorded.
In 2013, CollegeHumor created a parody trailer for a live-action Daria film starring Aubrey Plaza.
She appeared in The Simpsons episode "Bart vs. Itchy & Scratchy", on a poster of Cartoon Women's History.
She made a brief appearance in the Family Guy episode "Peter & Lois' Wedding", where a pre-handicapped Joe Swanson tried to flirt with her at the MTV Beach House in a flashback of the 1990s, only to be rejected.
Daria appears in the Robot Chicken episodes "Kramer vs. Showgirls" and "May Cause Weebles to Fall Down".
== Reception ==
Carol A. Stabile, author of Prime Time Animation: Television Animation and American Culture, said that "for the cerebral, writerly types who liked television Daria was the outcast she-hero who dared to say things they were too scared to say in their teenage years." Van Toffler, then the general manager of MTV, said in 1998 that Daria "has an attitude about parents, school, and siblings that is common to the experiences of our audience. She is a good spokesperson for MTV ... intelligent but subversive." A 1997 The Nation article referred to Daria as "a 10th grade Dorothy Parker". Another critic praising the character said that she is like "a 50-year-old deadpan Jewish comic in the body of a 16-year-old". Jennifer Vineyard, a writer of My Life as Liz, said "Daria made it cool to be a smart chick." Vineyard added, "Just the presence of people or characters like Daria help make it cool to be yourself. There's a tendency for young girls to play dumb. Characters like Daria show you that you don't have to."
Some commentators believed that the character's deadpan humor had too much morbidity for the teenage audience. A critic said that Daria uses her "omnivorous deadpan" contempt against other people, represented a variety of "living death", and was "a grim reaper in a dress" who was more dangerous than Marilyn Manson. Anita Gates of The New York Times said "And some people like her just because she says mean things. As far as I can tell, with her show well into its third season [...], Daria has never cracked a smile."
== References == | Daria Morgendorffer is a fictional character and the enponymous main protagonist of the MTV adult animated series Daria, which originally aired from March 1997 to January 2002. She was initially designed and created by Beavis and Butt-Head staff writer David Felton as a supporting character, serving as an intelligent foil to the two main characters. Eventually, MTV sought to make an animated show catered more to female viewers, and thus Glenn Eichler and Susie Lewis Lynn co-developed Daria. She was voiced in both productions by Tracy Grandstaff.
In 2002, Daria placed at number 41 on the list of the Top 50 Greatest Cartoon Characters of All Time by TV Guide for her role in the two shows. She was also listed in AOL's 100 Most Memorable Female TV Characters.
| 5 |
335 | internet connectivity | Internet access (wikipedia) | Internet access is a facility or service that provides connectivity for a computer, a computer network, or other network device to the Internet, and for individuals or organizations to access or use applications such as email and the World Wide Web. Internet access is offered for sale by an international hierarchy of Internet service providers (ISPs) using various networking technologies. At the retail level, many organizations, including municipal entities, also provide cost-free access to the general public.
The availability of Internet access to the general public began with the commercialization of the early Internet in the early 1990s, and has grown with the availability of useful applications, such as the World Wide Web. In 1995, only 0.04 percent of the world's population had access, with well over half of those living in the United States and consumer use was through dial-up. By the first decade of the 21st century, many consumers in developed nations used faster broadband technology. By 2014, 41 percent of the world's population had access, broadband was almost ubiquitous worldwide, and global average connection speeds exceeded one megabit per second. Types of connections range from fixed cable home (such as DSL and fiber optic) to mobile (via cellular) and satellite.
== History ==
The Internet developed from the ARPANET, which was funded by the US government to support projects within the government, at universities and research laboratories in the US, but grew over time to include most of the world's large universities and the research arms of many technology companies. Use by a wider audience only came in 1995 when restrictions on the use of the Internet to carry commercial traffic were lifted.
In the early to mid-1980s, most Internet access was from personal computers and workstations directly connected to local area networks (LANs) or from dial-up connections using modems and analog telephone lines. LANs typically operated at 10 Mbit/s while modem data-rates grew from 1200 bit/s in the early 1980s to 56 kbit/s by the late 1990s. Initially, dial-up connections were made from terminals or computers running terminal-emulation software to terminal servers on LANs. These dial-up connections did not support end-to-end use of the Internet protocols and only provided terminal-to-host connections. The introduction of network access servers supporting the Serial Line Internet Protocol (SLIP) and later the point-to-point protocol (PPP) extended the Internet protocols and made the full range of Internet services available to dial-up users; although slower, due to the lower data rates available using dial-up.
An important factor in the rapid rise of Internet access speed has been advances in MOSFET (MOS transistor) technology. The MOSFET, originally invented by Mohamed Atalla and Dawon Kahng in 1959, is the building block of the Internet telecommunications networks. The laser, originally demonstrated by Charles H. Townes and Arthur Leonard Schawlow in 1960, was adopted for MOS light-wave systems around 1980, which led to exponential growth of Internet bandwidth. Continuous MOSFET scaling has since led to online bandwidth doubling every 18 months (Edholm's law, which is related to Moore's law), with the bandwidths of telecommunications networks rising from bits per second to terabits per second.
Broadband Internet access, often shortened to just broadband, is simply defined as "Internet access that is always on, and faster than the traditional dial-up access" and so covers a wide range of technologies. The core of these broadband Internet technologies are complementary MOS (CMOS) digital circuits, the speed capabilities of which were extended with innovative design techniques. Broadband connections are typically made using a computer's built in Ethernet networking capabilities, or by using a NIC expansion card.
Most broadband services provide a continuous "always on" connection; there is no dial-in process required, and it does not interfere with voice use of phone lines. Broadband provides improved access to Internet services such as:
Faster World Wide Web browsing
Faster downloading of documents, photographs, videos, and other large files
Telephony, radio, television, and videoconferencing
Virtual private networks and remote system administration
Online gaming, especially massively multiplayer online role-playing games which are interaction-intensive
In the 1990s, the National Information Infrastructure initiative in the U.S. made broadband Internet access a public policy issue. In 2000, most Internet access to homes was provided using dial-up, while many businesses and schools were using broadband connections. In 2000 there were just under 150 million dial-up subscriptions in the 34 OECD countries and fewer than 20 million broadband subscriptions. By 2004, broadband had grown and dial-up had declined so that the number of subscriptions were roughly equal at 130 million each. In 2010, in the OECD countries, over 90% of the Internet access subscriptions used broadband, broadband had grown to more than 300 million subscriptions, and dial-up subscriptions had declined to fewer than 30 million.
The broadband technologies in widest use are of digital subscriber line (DSL), ADSL, and cable Internet access. Newer technologies include VDSL and optical fiber extended closer to the subscriber in both telephone and cable plants. Fiber-optic communication, while only recently being used in premises and to the curb schemes, has played a crucial role in enabling broadband Internet access by making transmission of information at very high data rates over longer distances much more cost-effective than copper wire technology.
In areas not served by ADSL or cable, some community organizations and local governments are installing Wi-Fi networks. Wireless, satellite, and microwave Internet are often used in rural, undeveloped, or other hard to serve areas where wired Internet is not readily available.
Newer technologies being deployed for fixed (stationary) and mobile broadband access include WiMAX, LTE, and fixed wireless.
Starting in roughly 2006, mobile broadband access is increasingly available at the consumer level using "3G" and "4G" technologies such as HSPA, EV-DO, HSPA+, and LTE.
== Availability ==
In addition to access from home, school, and the workplace Internet access may be available from public places such as libraries and Internet cafés, where computers with Internet connections are available. Some libraries provide stations for physically connecting users' laptops to LANs.
Wireless Internet access points are available in public places such as airport halls, in some cases just for brief use while standing. Some access points may also provide coin-operated computers. Various terms are used, such as "public Internet kiosk", "public access terminal", and "Web payphone". Many hotels also have public terminals, usually fee based.
Coffee shops, shopping malls, and other venues increasingly offer wireless access to computer networks, referred to as hotspots, for users who bring their own wireless-enabled devices such as a laptop or PDA. These services may be free to all, free to customers only, or fee-based. A Wi-Fi hotspot need not be limited to a confined location since multiple ones combined can cover a whole campus or park, or even an entire city can be enabled.
Additionally, mobile broadband access allows smartphones and other digital devices to connect to the Internet from any location from which a mobile phone call can be made, subject to the capabilities of that mobile network.
=== Speed ===
The bit rates for dial-up modems range from as little as 110 bit/s in the late 1950s, to a maximum of from 33 to 64 kbit/s (V.90 and V.92) in the late 1990s. Dial-up connections generally require the dedicated use of a telephone line. Data compression can boost the effective bit rate for a dial-up modem connection from 220 (V.42bis) to 320 (V.44) kbit/s. However, the effectiveness of data compression is quite variable, depending on the type of data being sent, the condition of the telephone line, and a number of other factors. In reality, the overall data rate rarely exceeds 150 kbit/s.
Broadband technologies supply considerably higher bit rates than dial-up, generally without disrupting regular telephone use. Various minimum data rates and maximum latencies have been used in definitions of broadband, ranging from 64 kbit/s up to 4.0 Mbit/s. In 1988 the CCITT standards body defined "broadband service" as requiring transmission channels capable of supporting bit rates greater than the primary rate which ranged from about 1.5 to 2 Mbit/s. A 2006 Organisation for Economic Co-operation and Development (OECD) report defined broadband as having download data transfer rates equal to or faster than 256 kbit/s. And in 2015 the U.S. Federal Communications Commission (FCC) defined "Basic Broadband" as data transmission speeds of at least 25 Mbit/s downstream (from the Internet to the user's computer) and 3 Mbit/s upstream (from the user's computer to the Internet). The trend is to raise the threshold of the broadband definition as higher data rate services become available.
The higher data rate dial-up modems and many broadband services are "asymmetric"—supporting much higher data rates for download (toward the user) than for upload (toward the Internet).
Data rates, including those given in this article, are usually defined and advertised in terms of the maximum or peak download rate. In practice, these maximum data rates are not always reliably available to the customer. Actual end-to-end data rates can be lower due to a number of factors. In late June 2016, internet connection speeds averaged about 6 Mbit/s globally. Physical link quality can vary with distance and for wireless access with terrain, weather, building construction, antenna placement, and interference from other radio sources. Network bottlenecks may exist at points anywhere on the path from the end-user to the remote server or service being used and not just on the first or last link providing Internet access to the end-user.
=== Network congestion ===
Users may share access over a common network infrastructure. Since most users do not use their full connection capacity all of the time, this aggregation strategy (known as contended service) usually works well, and users can burst to their full data rate at least for brief periods. However, peer-to-peer (P2P) file sharing and high-quality streaming video can require high data-rates for extended periods, which violates these assumptions and can cause a service to become oversubscribed, resulting in congestion and poor performance. The TCP protocol includes flow-control mechanisms that automatically throttle back on the bandwidth being used during periods of network congestion. This is fair in the sense that all users who experience congestion receive less bandwidth, but it can be frustrating for customers and a major problem for ISPs. In some cases, the amount of bandwidth actually available may fall below the threshold required to support a particular service such as video conferencing or streaming live video–effectively making the service unavailable.
When traffic is particularly heavy, an ISP can deliberately throttle back the bandwidth available to classes of users or for particular services. This is known as traffic shaping and careful use can ensure a better quality of service for time critical services even on extremely busy networks. However, overuse can lead to concerns about fairness and network neutrality or even charges of censorship, when some types of traffic are severely or completely blocked.
=== Outages ===
An Internet blackout or outage can be caused by local signaling interruptions. Disruptions of submarine communications cables may cause blackouts or slowdowns to large areas, such as in the 2008 submarine cable disruption. Less-developed countries are more vulnerable due to a small number of high-capacity links. Land cables are also vulnerable, as in 2011 when a woman digging for scrap metal severed most connectivity for the nation of Armenia. Internet blackouts affecting almost entire countries can be achieved by governments as a form of Internet censorship, as in the blockage of the Internet in Egypt, whereby approximately 93% of networks were without access in 2011 in an attempt to stop mobilization for anti-government protests.
On April 25, 1997, due to a combination of human error and a software bug, an incorrect routing table at MAI Network Service (a Virginia Internet service provider) propagated across backbone routers and caused major disruption to Internet traffic for a few hours.
== Technologies ==
When the Internet is accessed using a modem, digital data is converted to analog for transmission over analog networks such as the telephone and cable networks. A computer or other device accessing the Internet would either be connected directly to a modem that communicates with an Internet service provider (ISP) or the modem's Internet connection would be shared via a LAN which provides access in a limited area such as a home, school, computer laboratory, or office building.
Although a connection to a LAN may provide very high data-rates within the LAN, actual Internet access speed is limited by the upstream link to the ISP. LANs may be wired or wireless. Ethernet over twisted pair cabling and Wi-Fi are the two most common technologies used to build LANs today, but ARCNET, Token Ring, LocalTalk, FDDI, and other technologies were used in the past.
Ethernet is the name of the IEEE 802.3 standard for physical LAN communication and Wi-Fi is a trade name for a wireless local area network (WLAN) that uses one of the IEEE 802.11 standards. Ethernet cables are interconnected via switches & routers. Wi-Fi networks are built using one or more wireless antenna called access points.
Many "modems" (cable modems, DSL gateways or Optical Network Terminals (ONTs)) provide the additional functionality to host a LAN so most Internet access today is through a LAN such as that created by a WiFi router connected to a modem or a combo modem router, often a very small LAN with just one or two devices attached. And while LANs are an important form of Internet access, this raises the question of how and at what data rate the LAN itself is connected to the rest of the global Internet. The technologies described below are used to make these connections, or in other words, how customers' modems (Customer-premises equipment) are most often connected to internet service providers (ISPs).
=== Dial-up technologies ===
==== Dial-up access ====
Dial-up Internet access uses a modem and a phone call placed over the public switched telephone network (PSTN) to connect to a pool of modems operated by an ISP. The modem converts a computer's digital signal into an analog signal that travels over a phone line's local loop until it reaches a telephone company's switching facilities or central office (CO) where it is switched to another phone line that connects to another modem at the remote end of the connection.
Operating on a single channel, a dial-up connection monopolizes the phone line and is one of the slowest methods of accessing the Internet. Dial-up is often the only form of Internet access available in rural areas as it requires no new infrastructure beyond the already existing telephone network, to connect to the Internet. Typically, dial-up connections do not exceed a speed of 56 kbit/s, as they are primarily made using modems that operate at a maximum data rate of 56 kbit/s downstream (towards the end user) and 34 or 48 kbit/s upstream (toward the global Internet).
==== Multilink dial-up ====
Multilink dial-up provides increased bandwidth by channel bonding multiple dial-up connections and accessing them as a single data channel. It requires two or more modems, phone lines, and dial-up accounts, as well as an ISP that supports multilinking – and of course any line and data charges are also doubled. This inverse multiplexing option was briefly popular with some high-end users before ISDN, DSL and other technologies became available. Diamond and other vendors created special modems to support multilinking.
=== Hardwired broadband access ===
The term broadband includes a broad range of technologies, all of which provide higher data rate access to the Internet. The following technologies use wires or cables in contrast to wireless broadband described later.
==== Integrated Services Digital Network ====
Integrated Services Digital Network (ISDN) is a switched telephone service capable of transporting voice and digital data, and is one of the oldest Internet access methods. ISDN has been used for voice, video conferencing, and broadband data applications. ISDN was very popular in Europe, but less common in North America. Its use peaked in the late 1990s before the availability of DSL and cable modem technologies.
Basic rate ISDN, known as ISDN-BRI, has two 64 kbit/s "bearer" or "B" channels. These channels can be used separately for voice or data calls or bonded together to provide a 128 kbit/s service. Multiple ISDN-BRI lines can be bonded together to provide data rates above 128 kbit/s. Primary rate ISDN, known as ISDN-PRI, has 23 bearer channels (64 kbit/s each) for a combined data rate of 1.5 Mbit/s (US standard). An ISDN E1 (European standard) line has 30 bearer channels and a combined data rate of 1.9 Mbit/s. ISDN has been replaced by DSL technology, and it required special telephone switches at the service provider.
==== Leased lines ====
Leased lines are dedicated lines used primarily by ISPs, business, and other large enterprises to connect LANs and campus networks to the Internet using the existing infrastructure of the public telephone network or other providers. Delivered using wire, optical fiber, and radio, leased lines are used to provide Internet access directly as well as the building blocks from which several other forms of Internet access are created.
T-carrier technology dates to 1957 and provides data rates that range from 56 and 64 kbit/s (DS0) to 1.5 Mbit/s (DS1 or T1), to 45 Mbit/s (DS3 or T3). A T1 line carries 24 voice or data channels (24 DS0s), so customers may use some channels for data and others for voice traffic or use all 24 channels for clear channel data. A DS3 (T3) line carries 28 DS1 (T1) channels. Fractional T1 lines are also available in multiples of a DS0 to provide data rates between 56 and 1500 kbit/s. T-carrier lines require special termination equipment such as Data service units that may be separate from or integrated into a router or switch and which may be purchased or leased from an ISP. In Japan the equivalent standard is J1/J3. In Europe, a slightly different standard, E-carrier, provides 32 user channels (64 kbit/s) on an E1 (2.0 Mbit/s) and 512 user channels or 16 E1s on an E3 (34.4 Mbit/s).
Synchronous Optical Networking (SONET, in the U.S. and Canada) and Synchronous Digital Hierarchy (SDH, in the rest of the world) are the standard multiplexing protocols used to carry high-data-rate digital bit-streams over optical fiber using lasers or highly coherent light from light-emitting diodes (LEDs). At lower transmission rates data can also be transferred via an electrical interface. The basic unit of framing is an OC-3c (optical) or STS-3c (electrical) which carries 155.520 Mbit/s. Thus an OC-3c will carry three OC-1 (51.84 Mbit/s) payloads each of which has enough capacity to include a full DS3. Higher data rates are delivered in OC-3c multiples of four providing OC-12c (622.080 Mbit/s), OC-48c (2.488 Gbit/s), OC-192c (9.953 Gbit/s), and OC-768c (39.813 Gbit/s). The "c" at the end of the OC labels stands for "concatenated" and indicates a single data stream rather than several multiplexed data streams. Optical transport network (OTN) may be used instead of SONET for higher data transmission speeds of up to 400 Gbit/s per OTN channel.
The 1, 10, 40, and 100 Gigabit Ethernet IEEE standards (802.3) allow digital data to be delivered over copper wiring at distances to 100 m and over optical fiber at distances to 40 km.
==== Cable Internet access ====
Cable Internet provides access using a cable modem on hybrid fiber coaxial (HFC) wiring originally developed to carry television signals. Either fiber-optic or coaxial copper cable may connect a node to a customer's location at a connection known as a cable drop. Using a cable modem termination system, all nodes for cable subscribers in a neighborhood connect to a cable company's central office, known as the "head end." The cable company then connects to the Internet using a variety of means – usually fiber optic cable or digital satellite and microwave transmissions. Like DSL, broadband cable provides a continuous connection with an ISP.
Downstream, the direction toward the user, bit rates can be as much as 1000 Mbit/s in some countries, with the use of DOCSIS 3.1. Upstream traffic, originating at the user, ranges from 384 kbit/s to more than 50 Mbit/s. DOCSIS 4.0 promises up to 10 Gbit/s downstream and 6 Gbit/s upstream, however this technology is yet to have been implemented in real-world usage. Broadband cable access tends to service fewer business customers because existing television cable networks tend to service residential buildings; commercial buildings do not always include wiring for coaxial cable networks. In addition, because broadband cable subscribers share the same local line, communications may be intercepted by neighboring subscribers. Cable networks regularly provide encryption schemes for data traveling to and from customers, but these schemes may be thwarted.
==== Digital subscriber line (DSL, ADSL, SDSL, and VDSL) ====
Digital subscriber line (DSL) service provides a connection to the Internet through the telephone network. Unlike dial-up, DSL can operate using a single phone line without preventing normal use of the telephone line for voice phone calls. DSL uses the high frequencies, while the low (audible) frequencies of the line are left free for regular telephone communication. These frequency bands are subsequently separated by filters installed at the customer's premises.
DSL originally stood for "digital subscriber loop". In telecommunications marketing, the term digital subscriber line is widely understood to mean asymmetric digital subscriber line (ADSL), the most commonly installed variety of DSL. The data throughput of consumer DSL services typically ranges from 256 kbit/s to 20 Mbit/s in the direction to the customer (downstream), depending on DSL technology, line conditions, and service-level implementation. In ADSL, the data throughput in the upstream direction, (i.e., in the direction to the service provider) is lower than that in the downstream direction (i.e. to the customer), hence the designation of asymmetric. With a symmetric digital subscriber line (SDSL), the downstream and upstream data rates are equal.
Very-high-bit-rate digital subscriber line (VDSL or VHDSL, ITU G.993.1) is a digital subscriber line (DSL) standard approved in 2001 that provides data rates up to 52 Mbit/s downstream and 16 Mbit/s upstream over copper wires and up to 85 Mbit/s down- and upstream on coaxial cable. VDSL is capable of supporting applications such as high-definition television, as well as telephone services (voice over IP) and general Internet access, over a single physical connection.
VDSL2 (ITU-T G.993.2) is a second-generation version and an enhancement of VDSL. Approved in February 2006, it is able to provide data rates exceeding 100 Mbit/s simultaneously in both the upstream and downstream directions. However, the maximum data rate is achieved at a range of about 300 meters and performance degrades as distance and loop attenuation increases.
==== DSL Rings ====
DSL Rings (DSLR) or Bonded DSL Rings is a ring topology that uses DSL technology over existing copper telephone wires to provide data rates of up to 400 Mbit/s.
==== Fiber to the home ====
Fiber-to-the-home (FTTH) is one member of the Fiber-to-the-x (FTTx) family that includes Fiber-to-the-building or basement (FTTB), Fiber-to-the-premises (FTTP), Fiber-to-the-desk (FTTD), Fiber-to-the-curb (FTTC), and Fiber-to-the-node (FTTN). These methods all bring data closer to the end user on optical fibers. The differences between the methods have mostly to do with just how close to the end user the delivery on fiber comes. All of these delivery methods are similar in function and architecture to hybrid fiber-coaxial (HFC) systems used to provide cable Internet access. Fiber internet connections to customers are either AON (Active optical network) or more commonly PON (Passive optical network). Examples of fiber optic internet access standards are G.984 (GPON, G-PON) and 10G-PON (XG-PON). ISPs may instead use Metro Ethernet as a replacement for T1 and Frame Relay lines for corporate and institutional customers, or offer carrier-grade Ethernet.
The use of optical fiber offers much higher data rates over relatively longer distances. Most high-capacity Internet and cable television backbones already use fiber optic technology, with data switched to other technologies (DSL, cable, LTE) for final delivery to customers. Fiber optic is immune to electromagnetic interference.
In 2010, Australia began rolling out its National Broadband Network across the country using fiber-optic cables to 93 percent of Australian homes, schools, and businesses. The project was abandoned by the subsequent LNP government, in favor of a hybrid FTTN design, which turned out to be more expensive and introduced delays. Similar efforts are underway in Italy, Canada, India, and many other countries (see Fiber to the premises by country).
==== Power-line Internet ====
Power-line Internet, also known as Broadband over power lines (BPL), carries Internet data on a conductor that is also used for electric power transmission. Because of the extensive power line infrastructure already in place, this technology can provide people in rural and low population areas access to the Internet with little cost in terms of new transmission equipment, cables, or wires. Data rates are asymmetric and generally range from 256 kbit/s to 2.7 Mbit/s.
Because these systems use parts of the radio spectrum allocated to other over-the-air communication services, interference between the services is a limiting factor in the introduction of power-line Internet systems. The IEEE P1901 standard specifies that all power-line protocols must detect existing usage and avoid interfering with it.
Power-line Internet has developed faster in Europe than in the U.S. due to a historical difference in power system design philosophies. Data signals cannot pass through the step-down transformers used and so a repeater must be installed on each transformer. In the U.S. a transformer serves a small cluster of from one to a few houses. In Europe, it is more common for a somewhat larger transformer to service larger clusters of from 10 to 100 houses. Thus a typical U.S. city requires an order of magnitude more repeaters than a comparable European city.
==== ATM and Frame Relay ====
Asynchronous Transfer Mode (ATM) and Frame Relay are wide-area networking standards that can be used to provide Internet access directly or as building blocks of other access technologies. For example, many DSL implementations use an ATM layer over the low-level bitstream layer to enable a number of different technologies over the same link. Customer LANs are typically connected to an ATM switch or a Frame Relay node using leased lines at a wide range of data rates.
While still widely used, with the advent of Ethernet over optical fiber, MPLS, VPNs and broadband services such as cable modem and DSL, ATM and Frame Relay no longer play the prominent role they once did.
=== Wireless broadband access ===
Wireless broadband is used to provide both fixed and mobile Internet access with the following technologies.
==== Satellite broadband ====
Satellite Internet access provides fixed, portable, and mobile Internet access. Data rates range from 2 kbit/s to 1 Gbit/s downstream and from 2 kbit/s to 10 Mbit/s upstream. In the northern hemisphere, satellite antenna dishes require a clear line of sight to the southern sky, due to the equatorial position of all geostationary satellites. In the southern hemisphere, this situation is reversed, and dishes are pointed north. Service can be adversely affected by moisture, rain, and snow (known as rain fade). The system requires a carefully aimed directional antenna.
Satellites in geostationary Earth orbit (GEO) operate in a fixed position 35,786 km (22,236 mi) above the Earth's equator. At the speed of light (about 300,000 km/s or 186,000 miles per second), it takes a quarter of a second for a radio signal to travel from the Earth to the satellite and back. When other switching and routing delays are added and the delays are doubled to allow for a full round-trip transmission, the total delay can be 0.75 to 1.25 seconds. This latency is large when compared to other forms of Internet access with typical latencies that range from 0.015 to 0.2 seconds. Long latencies negatively affect some applications that require real-time response, particularly online games, voice over IP, and remote control devices. TCP tuning and TCP acceleration techniques can mitigate some of these problems. GEO satellites do not cover the Earth's polar regions. HughesNet, Exede, AT&T and Dish Network have GEO systems.
Satellite internet constellations in low Earth orbit (LEO, below 2,000 km or 1,243 miles) and medium Earth orbit (MEO, between 2,000 and 35,786 km or 1,243 and 22,236 miles) operate at lower altitudes, and their satellites are not fixed in their position above the Earth. Because they operate at a lower altitude, more satellites and launch vehicles are needed for worldwide coverage. This makes the initial required investment very large which initially caused OneWeb and Iridium to declare bankruptcy. However, their lower altitudes allow lower latencies and higher speeds which make real-time interactive Internet applications more feasible. LEO systems include Globalstar, Starlink, OneWeb and Iridium. The O3b constellation is a medium Earth-orbit system with a latency of 125 ms. COMMStellation™ is a LEO system, scheduled for launch in 2015, that is expected to have a latency of just 7 ms.
==== Mobile broadband ====
Mobile broadband is the marketing term for wireless Internet access delivered through mobile phone towers (cellular networks) to computers, mobile phones (called "cell phones" in North America and South Africa, and "hand phones" in Asia), and other digital devices using portable modems. Some mobile services allow more than one device to be connected to the Internet using a single cellular connection using a process called tethering. The modem may be built into laptop computers, tablets, mobile phones, and other devices, added to some devices using PC cards, USB modems, and USB sticks or dongles, or separate wireless modems can be used.
New mobile phone technology and infrastructure is introduced periodically and generally involves a change in the fundamental nature of the service, non-backwards-compatible transmission technology, higher peak data rates, new frequency bands, wider channel frequency bandwidth in Hertz becomes available. These transitions are referred to as generations. The first mobile data services became available during the second generation (2G).
The download (to the user) and upload (to the Internet) data rates given above are peak or maximum rates and end users will typically experience lower data rates.
WiMAX was originally developed to deliver fixed wireless service with wireless mobility added in 2005. CDPD, CDMA2000 EV-DO, and MBWA are no longer being actively developed.
In 2011, 90% of the world's population lived in areas with 2G coverage, while 45% lived in areas with 2G and 3G coverage.
5G was designed to be faster and have lower latency than its predecessor, 4G. It can be used for mobile broadband in smartphones or separate modems that emit WiFi or can be connected through USB to a computer, or for fixed wireless.
==== Fixed wireless ====
Fixed wireless internet connections that do not use a satellite nor are designed to support moving equipment such as smartphones due to the use of, for example, customer premises equipment such as antennas that can't be moved over a significant geographical area without losing the signal from the ISP, unlike smartphones. Microwave wireless broadband or 5G may be used for fixed wireless.
===== WiMAX =====
Worldwide Interoperability for Microwave Access (WiMAX) is a set of interoperable implementations of the IEEE 802.16 family of wireless-network standards certified by the WiMAX Forum. It enables "the delivery of last mile wireless broadband access as an alternative to cable and DSL". The original IEEE 802.16 standard, now called "Fixed WiMAX", was published in 2001 and provided 30 to 40 megabit-per-second data rates. Mobility support was added in 2005. A 2011 update provides data rates up to 1 Gbit/s for fixed stations. WiMax offers a metropolitan area network with a signal radius of about 50 km (30 miles), far surpassing the 30-metre (100-foot) wireless range of a conventional Wi-Fi LAN. WiMAX signals also penetrate building walls much more effectively than Wi-Fi. WiMAX is most often used as a fixed wireless standard.
===== Wireless ISP =====
Wireless Internet service providers (WISPs) operate independently of mobile phone operators. WISPs typically employ low-cost IEEE 802.11 Wi-Fi radio systems to link up remote locations over great distances (Long-range Wi-Fi), but may use other higher-power radio communications systems as well, such as microwave and WiMAX.
Traditional 802.11a/b/g/n/ac is an unlicensed omnidirectional service designed to span between 100 and 150 m (300 to 500 ft). By focusing the radio signal using a directional antenna (where allowed by regulations), 802.11 can operate reliably over a distance of many km(miles), although the technology's line-of-sight requirements hamper connectivity in areas with hilly or heavily foliated terrain. In addition, compared to hard-wired connectivity, there are security risks (unless robust security protocols are enabled); data rates are usually slower (2 to 50 times slower); and the network can be less stable, due to interference from other wireless devices and networks, weather and line-of-sight problems.
With the increasing popularity of unrelated consumer devices operating on the same 2.4 GHz band, many providers have migrated to the 5GHz ISM band. If the service provider holds the necessary spectrum license, it could also reconfigure various brands of off the shelf Wi-Fi hardware to operate on its own band instead of the crowded unlicensed ones. Using higher frequencies carries various advantages:
usually regulatory bodies allow for more power and using (better-) directional antennae,
there exists much more bandwidth to share, allowing both better throughput and improved coexistence,
there are fewer consumer devices that operate over 5 GHz than over 2.4 GHz, hence fewer interferers are present,
the shorter wavelengths don't propagate as well through walls and other structures, so much less interference leaks outside of the homes of consumers.
Proprietary technologies like Motorola Canopy & Expedience can be used by a WISP to offer wireless access to rural and other markets that are hard to reach using Wi-Fi or WiMAX. There are a number of companies that provide this service.
===== Local Multipoint Distribution Service =====
Local Multipoint Distribution Service (LMDS) is a broadband wireless access technology that uses microwave signals operating between 26 GHz and 29 GHz. Originally designed for digital television transmission (DTV), it is conceived as a fixed wireless, point-to-multipoint technology for utilization in the last mile. Data rates range from 64 kbit/s to 155 Mbit/s. Distance is typically limited to about 1.5 miles (2.4 km), but links of up to 5 miles (8 km) from the base station are possible in some circumstances.
LMDS has been surpassed in both technological and commercial potential by the LTE and WiMAX standards.
=== Hybrid Access Networks ===
In some regions, notably in rural areas, the length of the copper lines makes it difficult for network operators to provide high-bandwidth services. One alternative is to combine a fixed-access network, typically XDSL, with a wireless network, typically LTE. The Broadband Forum has standardized an architecture for such Hybrid Access Networks.
=== Non-commercial alternatives for using Internet services ===
==== Grassroots wireless networking movements ====
Deploying multiple adjacent Wi-Fi access points is sometimes used to create city-wide wireless networks. It is usually ordered by the local municipality from commercial WISPs.
Grassroots efforts have also led to wireless community networks widely deployed in numerous countries, both developing and developed ones. Rural wireless-ISP installations are typically not commercial in nature and are instead a patchwork of systems built up by hobbyists mounting antennas on radio masts and towers, agricultural storage silos, very tall trees, or whatever other tall objects are available.
Where radio spectrum regulation is not community-friendly, the channels are crowded or when equipment can not be afforded by local residents, free-space optical communication can also be deployed in a similar manner for point to point transmission in air (rather than in fiber optic cable).
==== Packet radio ====
Packet radio connects computers or whole networks operated by radio amateurs with the option to access the Internet. Note that as per the regulatory rules outlined in the HAM license, Internet access and email should be strictly related to the activities of hardware amateurs.
==== Sneakernet ====
The term, a tongue-in-cheek play on net(work) as in Internet or Ethernet, refers to the wearing of sneakers as the transport mechanism for the data.
For those who do not have access to or can not afford broadband at home, downloading large files and disseminating information is done by transmission through workplace or library networks, taken home and shared with neighbors by sneakernet. The Cuban El Paquete Semanal is an organized example of this.
There are various decentralized, delay tolerant peer to peer applications which aim to fully automate this using any available interface, including both wireless (Bluetooth, Wi-Fi mesh, P2P or hotspots) and physically connected ones (USB storage, Ethernet, etc.).
Sneakernets may also be used in tandem with computer network data transfer to increase data security or overall throughput for big data use cases. Innovation continues in the area to this day; for example, AWS has recently announced Snowball, and bulk data processing is also done in a similar fashion by many research institutes and government agencies.
== Pricing and spending ==
Internet access is limited by the relation between pricing and available resources to spend. Regarding the latter, it is estimated that 40% of the world's population has less than US$20 per year available to spend on information and communications technology (ICT). In Mexico, the poorest 30% of the society spend an estimated US$35 per year (US$3 per month) and in Brazil, the poorest 22% of the population merely has US$9 per year to spend on ICT (US$0.75 per month). From Latin America, it is known that the borderline between ICT as a necessity good and ICT as a luxury good is roughly around the "magical number" of US$10 per person per month, or US$120 per year. This is the amount of ICT spending people esteem to be a basic necessity. Current Internet access prices exceed the available resources by large in many countries.
Dial-up users pay the costs for making local or long-distance phone calls, usually pay a monthly subscription fee, and may be subject to additional per minute or traffic based charges, and connect time limits by their ISP. Though less common today than in the past, some dial-up access is offered for "free" in return for watching banner ads as part of the dial-up service. NetZero, BlueLight, Juno, Freenet (NZ), and Free-nets are examples of services providing free access. Some Wireless community networks continue the tradition of providing free Internet access.
Fixed broadband Internet access is often sold under an "unlimited" or flat rate pricing model, with price determined by the maximum data rate chosen by the customer, rather than a per minute or traffic based charge. Per minute and traffic based charges and traffic caps are common for mobile broadband Internet access.
Internet services like Facebook, Wikipedia and Google have built special programs to partner with mobile network operators (MNO) to introduce zero-rating the cost for their data volumes as a means to provide their service more broadly into developing markets.
With increased consumer demand for streaming content such as video on demand and peer-to-peer file sharing, demand for bandwidth has increased rapidly and for some ISPs the flat rate pricing model may become unsustainable. However, with fixed costs estimated to represent 80–90% of the cost of providing broadband service, the marginal cost to carry additional traffic is low. Most ISPs do not disclose their costs, but the cost to transmit a gigabyte of data in 2011 was estimated to be about $0.03.
Some ISPs estimate that a small number of their users consume a disproportionate portion of the total bandwidth. In response some ISPs are considering, are experimenting with, or have implemented combinations of traffic based pricing, time of day or "peak" and "off peak" pricing, and bandwidth or traffic caps. Others claim that because the marginal cost of extra bandwidth is very small with 80 to 90 percent of the costs fixed regardless of usage level, that such steps are unnecessary or motivated by concerns other than the cost of delivering bandwidth to the end user.
In Canada, Rogers Hi-Speed Internet and Bell Canada have imposed bandwidth caps. In 2008 Time Warner began experimenting with usage-based pricing in Beaumont, Texas. In 2009 an effort by Time Warner to expand usage-based pricing into the Rochester, New York area met with public resistance, however, and was abandoned.
On August 1, 2012, in Nashville, Tennessee and on October 1, 2012, in Tucson, Arizona Comcast began tests that impose data caps on area residents. In Nashville exceeding the 300 Gbyte cap mandates a temporary purchase of 50 Gbytes of additional data.
== Digital divide ==
Despite its tremendous growth, Internet access is not distributed equally within or between countries. The digital divide refers to "the gap between people with effective access to information and communications technology (ICT), and those with very limited or no access". The gap between people with Internet access and those without is one of many aspects of the digital divide. Whether someone has access to the Internet can depend greatly on financial status, geographical location as well as government policies. "Low-income, rural, and minority populations have received special scrutiny as the technological 'have-nots'."
Government policies play a tremendous role in bringing Internet access to or limiting access for underserved groups, regions, and countries. For example, in Pakistan, which is pursuing an aggressive IT policy aimed at boosting its drive for economic modernization, the number of Internet users grew from 133,900 (0.1% of the population) in 2000 to 31 million (17.6% of the population) in 2011. In North Korea there is relatively little access to the Internet due to the governments' fear of political instability that might accompany the benefits of access to the global Internet. The U.S. trade embargo is a barrier limiting Internet access in Cuba.
Access to computers is a dominant factor in determining the level of Internet access. In 2011, in developing countries, 25% of households had a computer and 20% had Internet access, while in developed countries the figures were 74% of households had a computer and 71% had Internet access. The majority of people in developing countries do not have Internet access. About 4 billion people do not have Internet access. When buying computers was legalized in Cuba in 2007, the private ownership of computers soared (there were 630,000 computers available on the island in 2008, a 23% increase over 2007).
Internet access has changed the way in which many people think and has become an integral part of people's economic, political, and social lives. The United Nations has recognized that providing Internet access to more people in the world will allow them to take advantage of the "political, social, economic, educational, and career opportunities" available over the Internet. Several of the 67 principles adopted at the World Summit on the Information Society convened by the United Nations in Geneva in 2003, directly address the digital divide. To promote economic development and a reduction of the digital divide, national broadband plans have been and are being developed to increase the availability of affordable high-speed Internet access throughout the world. The Global Gateway, the EU's initiative to assist infrastructure development throughout the world, plans to raise €300 billion for connectivity projects, including those in the digital sector, between 2021 and 2027.
=== Growth in number of users ===
Access to the Internet grew from an estimated 10 million people in 1993, to almost 40 million in 1995, to 670 million in 2002, and to 2.7 billion in 2013. With market saturation, growth in the number of Internet users is slowing in industrialized countries, but continues in Asia, Africa, Latin America, the Caribbean, and the Middle East. Across Africa, an estimated 900 million people are still not connected to the internet; for those who are, connectivity fees remain generally expensive, and bandwidth is severely constrained in many locations. The number of mobile customers in Africa, however, is expanding faster than everywhere else. Mobile financial services also allow for immediate payment of products and services.
There were roughly 0.6 billion fixed broadband subscribers and almost 1.2 billion mobile broadband subscribers in 2011. In developed countries people frequently use both fixed and mobile broadband networks. In developing countries mobile broadband is often the only access method available.
=== Bandwidth divide ===
Traditionally the divide has been measured in terms of the existing numbers of subscriptions and digital devices ("have and have-not of subscriptions"). Recent studies have measured the digital divide not in terms of technological devices, but in terms of the existing bandwidth per individual (in kbit/s per capita). As shown in the Figure on the side, the digital divide in kbit/s is not monotonically decreasing, but re-opens up with each new innovation. For example, "the massive diffusion of narrow-band Internet and mobile phones during the late 1990s" increased digital inequality, as well as "the initial introduction of broadband DSL and cable modems during 2003–2004 increased levels of inequality". This is because a new kind of connectivity is never introduced instantaneously and uniformly to society as a whole at once, but diffuses slowly through social networks. As shown by the Figure, during the mid-2000s, communication capacity was more unequally distributed than during the late 1980s, when only fixed-line phones existed. The most recent increase in digital equality stems from the massive diffusion of the latest digital innovations (i.e. fixed and mobile broadband infrastructures, e.g. 3G and fiber optics FTTH). As shown in the Figure, Internet access in terms of bandwidth is more unequally distributed in 2014 as it was in the mid-1990s.
For example, only 0.4% of the African population has a fixed-broadband subscription. The majority of internet users use it through mobile broadband.
=== Rural access ===
One of the great challenges for Internet access in general and for broadband access in particular is to provide service to potential customers in areas of low population density, such as to farmers, ranchers, and small towns. In cities where the population density is high, it is easier for a service provider to recover equipment costs, but each rural customer may require expensive equipment to get connected. While 66% of Americans had an Internet connection in 2010, that figure was only 50% in rural areas, according to the Pew Internet & American Life Project.
Virgin Media advertised over 100 towns across the United Kingdom "from Cwmbran to Clydebank" that have access to their 100 Mbit/s service.
Wireless Internet service providers (WISPs) are rapidly becoming a popular broadband option for rural areas. The technology's line-of-sight requirements may hamper connectivity in some areas with hilly and heavily foliated terrain. However, the Tegola project, a successful pilot in remote Scotland, demonstrates that wireless can be a viable option.
The Broadband for Rural Nova Scotia initiative is the first program in North America to guarantee access to "100% of civic addresses" in a region. It is based on Motorola Canopy technology. As of November 2011, under 1000 households have reported access problems. Deployment of a new cell network by one Canopy provider (Eastlink) was expected to provide the alternative of 3G/4G service, possibly at a special unmetered rate, for areas harder to serve by Canopy.
In New Zealand, a fund has been formed by the government to improve rural broadband, and mobile phone coverage. Current proposals include: (a) extending fiber coverage and upgrading copper to support VDSL, (b) focusing on improving the coverage of cellphone technology, or (c) regional wireless.
Several countries have started Hybrid Access Networks to provide faster Internet services in rural areas by enabling network operators to efficiently combine their XDSL and LTE networks.
=== Access as a civil or human right ===
The actions, statements, opinions, and recommendations outlined below have led to the suggestion that Internet access itself is or should become a civil or perhaps a human right.
Several countries have adopted laws requiring the state to work to ensure that Internet access is broadly available or preventing the state from unreasonably restricting an individual's access to information and the Internet:
Costa Rica: A 30 July 2010 ruling by the Supreme Court of Costa Rica stated: "Without fear of equivocation, it can be said that these technologies [information technology and communication] have impacted the way humans communicate, facilitating the connection between people and institutions worldwide and eliminating barriers of space and time. At this time, access to these technologies becomes a basic tool to facilitate the exercise of fundamental rights and democratic participation (e-democracy) and citizen control, education, freedom of thought and expression, access to information and public services online, the right to communicate with the government electronically and administrative transparency, among others. This includes the fundamental right of access to these technologies, in particular, the right of access to the Internet or World Wide Web."
Estonia: In 2000, the parliament launched a massive program to expand access to the countryside. The Internet, the government argues, is essential for life in the twenty-first century.
Finland: By July 2010, every person in Finland was to have access to a one-megabit per second broadband connection, according to the Ministry of Transport and Communications. And by 2015, access to a 100 Mbit/s connection.
France: In June 2009, the Constitutional Council, France's highest court, declared access to the Internet to be a basic human right in a strongly-worded decision that struck down portions of the HADOPI law, a law that would have tracked abusers and without judicial review automatically cut off network access to those who continued to download illicit material after two warnings
Greece: Article 5A of the Constitution of Greece states that all persons has a right to participate in the Information Society and that the state has an obligation to facilitate the production, exchange, diffusion, and access to electronically transmitted information.
Spain: Starting in 2011, Telefónica, the former state monopoly that holds the country's "universal service" contract, has to guarantee to offer "reasonably" priced broadband of at least one megabyte per second throughout Spain.
In December 2003, the World Summit on the Information Society (WSIS) was convened under the auspice of the United Nations. After lengthy negotiations between governments, businesses and civil society representatives the WSIS Declaration of Principles was adopted reaffirming the importance of the Information Society to maintaining and strengthening human rights:
1. We, the representatives of the peoples of the world, assembled in Geneva from 10–12 December 2003 for the first phase of the World Summit on the Information Society, declare our common desire and commitment to build a people-centered, inclusive and development-oriented Information Society, where everyone can create, access, utilize and share information and knowledge, enabling individuals, communities and peoples to achieve their full potential in promoting their sustainable development and improving their quality of life, premised on the purposes and principles of the Charter of the United Nations and respecting fully and upholding the Universal Declaration of Human Rights.
3. We reaffirm the universality, indivisibility, interdependence and interrelation of all human rights and fundamental freedoms, including the right to development, as enshrined in the Vienna Declaration. We also reaffirm that democracy, sustainable development, and respect for human rights and fundamental freedoms as well as good governance at all levels are interdependent and mutually reinforcing. We further resolve to strengthen the rule of law in international as in national affairs.
The WSIS Declaration of Principles makes specific reference to the importance of the right to freedom of expression in the "Information Society" in stating:
4. We reaffirm, as an essential foundation of the Information Society, and as outlined in Article 19 of the Universal Declaration of Human Rights, that everyone has the right to freedom of opinion and expression; that this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers. Communication is a fundamental social process, a basic human need and the foundation of all social organization. It is central to the Information Society. Everyone, everywhere should have the opportunity to participate and no one should be excluded from the benefits of the Information Society offers."
A poll of 27,973 adults in 26 countries, including 14,306 Internet users, conducted for the BBC World Service between 30 November 2009 and 7 February 2010 found that almost four in five Internet users and non-users around the world felt that access to the Internet was a fundamental right. 50% strongly agreed, 29% somewhat agreed, 9% somewhat disagreed, 6% strongly disagreed, and 6% gave no opinion.
The 88 recommendations made by the Special Rapporteur on the promotion and protection of the right to freedom of opinion and expression in a May 2011 report to the Human Rights Council of the United Nations General Assembly include several that bear on the question of the right to Internet access:
67. Unlike any other medium, the Internet enables individuals to seek, receive and impart information and ideas of all kinds instantaneously and inexpensively across national borders. By vastly expanding the capacity of individuals to enjoy their right to freedom of opinion and expression, which is an "enabler" of other human rights, the Internet boosts economic, social and political development, and contributes to the progress of humankind as a whole. In this regard, the Special Rapporteur encourages other Special Procedures mandate holders to engage on the issue of the Internet with respect to their particular mandates.
78. While blocking and filtering measures deny users access to specific content on the Internet, States have also taken measures to cut off access to the Internet entirely. The Special Rapporteur considers cutting off users from Internet access, regardless of the justification provided, including on the grounds of violating intellectual property rights law, to be disproportionate and thus a violation of article 19, paragraph 3, of the International Covenant on Civil and Political Rights.
79. The Special Rapporteur calls upon all States to ensure that Internet access is maintained at all times, including during times of political unrest.
85. Given that the Internet has become an indispensable tool for realizing a range of human rights, combating inequality, and accelerating development and human progress, ensuring universal access to the Internet should be a priority for all States. Each State should thus develop a concrete and effective policy, in consultation with individuals from all sections of society, including the private sector and relevant Government ministries, to make the Internet widely available, accessible and affordable to all segments of population.
=== Network neutrality ===
Network neutrality (also net neutrality, Internet neutrality, or net equality) is the principle that Internet service providers and governments should treat all data on the Internet equally, not discriminating or charging differentially by user, content, site, platform, application, type of attached equipment, or mode of communication. Advocates of net neutrality have raised concerns about the ability of broadband providers to use their last mile infrastructure to block Internet applications and content (e.g. websites, services, and protocols), and even to block out competitors. Opponents claim net neutrality regulations would deter investment into improving broadband infrastructure and try to fix something that isn't broken. In April 2017, a recent attempt to compromise net neutrality in the United States is being considered by the newly appointed FCC chairman, Ajit Varadaraj Pai. The vote on whether or not to abolish net neutrality was passed on December 14, 2017, and ended in a 3–2 split in favor of abolishing net neutrality.
== Natural disasters and access ==
Natural disasters disrupt internet access in profound ways. This is important—not only for telecommunication companies who own the networks and the businesses who use them, but for emergency crew and displaced citizens as well. The situation is worsened when hospitals or other buildings necessary for disaster response lose their connection. Knowledge gained from studying past internet disruptions by natural disasters could be put to use in planning or recovery. Additionally, because of both natural and man-made disasters, studies in network resiliency are now being conducted to prevent large-scale outages.
One way natural disasters impact internet connection is by damaging end sub-networks (subnets), making them unreachable. A study on local networks after Hurricane Katrina found that 26% of subnets within the storm coverage were unreachable. At Hurricane Katrina's peak intensity, almost 35% of networks in Mississippi were without power, while around 14% of Louisiana's networks were disrupted. Of those unreachable subnets, 73% were disrupted for four weeks or longer and 57% were at "network edges were important emergency organizations such as hospitals and government agencies are mostly located". Extensive infrastructure damage and inaccessible areas were two explanations for the long delay in returning service. The company Cisco has revealed a Network Emergency Response Vehicle (NERV), a truck that makes portable communications possible for emergency responders despite traditional networks being disrupted.
A second way natural disasters destroy internet connectivity is by severing submarine cables—fiber-optic cables placed on the ocean floor that provide international internet connection. A sequence of undersea earthquakes cut six out of seven international cables connected to Taiwan and caused a tsunami that wiped out one of its cable and landing stations. The impact slowed or disabled internet connection for five days within the Asia-Pacific region as well as between the region and the United States and Europe.
With the rise in popularity of cloud computing, concern has grown over access to cloud-hosted data in the event of a natural disaster. Amazon Web Services (AWS) has been in the news for major network outages in April 2011 and June 2012. AWS, like other major cloud hosting companies, prepares for typical outages and large-scale natural disasters with backup power as well as backup data centers in other locations. AWS divides the globe into five regions and then splits each region into availability zones. A data center in one availability zone should be backed up by a data center in a different availability zone. Theoretically, a natural disaster would not affect more than one availability zone. This theory plays out as long as human error is not added to the mix. The June 2012 major storm only disabled the primary data center, but human error disabled the secondary and tertiary backups, affecting companies such as Netflix, Pinterest, Reddit, and Instagram.
== See also ==
== References ==
== External links ==
European broadband
Corporate vs. Community Internet Archived 2011-05-09 at the Wayback Machine, AlterNet, June 14, 2005, – on the clash between US cities' attempts to expand municipal broadband and corporate attempts to defend their markets
Broadband data, from Google public data
FCC Broadband Map
Types of Broadband Connections Archived 2018-03-11 at the Wayback Machine, Broadband.gov | Internet access is a facility or service that provides connectivity for a computer, a computer network, or other network device to the Internet, and for individuals or organizations to access or use applications such as email and the World Wide Web. Internet access is offered for sale by an international hierarchy of Internet service providers (ISPs) using various networking technologies. At the retail level, many organizations, including municipal entities, also provide cost-free access to the general public.
The availability of Internet access to the general public began with the commercialization of the early Internet in the early 1990s, and has grown with the availability of useful applications, such as the World Wide Web. In 1995, only 0.04 percent of the world's population had access, with well over half of those living in the United States and consumer use was through dial-up. By the first decade of the 21st century, many consumers in developed nations used faster broadband technology. By 2014, 41 percent of the world's population had access, broadband was almost ubiquitous worldwide, and global average connection speeds exceeded one megabit per second. Types of connections range from fixed cable home (such as DSL and fiber optic) to mobile (via cellular) and satellite.
| 7 |
336 | browser | Browser (wiktionary) | Borrowed from English browser, from browse + -er.
IPA(key): /ˈbʁaʊ̯zɐ/
Browser m (strong, genitive Browsers, plural Browser)
(computing) A browser program
browsen
“Browser” in Duden online
“Browser” in Digitales Wörterbuch der deutschen Sprache | Borrowed from English browser, from browse + -er.
IPA(key): /ˈbʁaʊ̯zɐ/
Browser m (strong, genitive Browsers, plural Browser)
(computing) A browser program
browsen
“Browser” in Duden online
“Browser” in Digitales Wörterbuch der deutschen Sprache | 6 |
337 | browser | browser (wiktionary) | browse + -er
IPA(key): /ˈbɹaʊzɚ/
Hyphenation: brows‧er
Rhymes: -aʊzə(ɹ)
browser (plural browsers)
A person or animal who browses.
Coordinate term: grazer
A person who examines goods for sale but purchases nothing.
Antonym: nonbrowser
(computing) A web browser.
browser on Wikipedia.Wikipedia
Browers
Borrowed from English browser. First attested in 1993..
IPA(key): /bravsər/, [ˈbɹɑwsɐ]
browser c (singular definite browseren, plural indefinite browsere)
browser
browser on the Danish Wikipedia.Wikipedia da
Borrowed from English browser.
IPA(key): /ˈbrɑu̯.zər/
Hyphenation: brow‧ser
browser m (plural browsers)
(Internet) A browser.
Synonym: internetbrowser
browsen
Unadapted borrowing from English browser.
browser m (invariable)
(computing) browser (software)
browser m (plural browseres)
browser | browse + -er
IPA(key): /ˈbɹaʊzɚ/
Hyphenation: brows‧er
Rhymes: -aʊzə(ɹ)
browser (plural browsers)
A person or animal who browses.
Coordinate term: grazer
A person who examines goods for sale but purchases nothing.
Antonym: nonbrowser
(computing) A web browser.
browser on Wikipedia.Wikipedia
Browers
Borrowed from English browser. First attested in 1993..
IPA(key): /bravsər/, [ˈbɹɑwsɐ]
browser c (singular definite browseren, plural indefinite browsere)
browser
browser on the Danish Wikipedia.Wikipedia da
Borrowed from English browser.
IPA(key): /ˈbrɑu̯.zər/
Hyphenation: brow‧ser
browser m (plural browsers)
(Internet) A browser.
Synonym: internetbrowser
browsen
Unadapted borrowing from English browser.
browser m (invariable)
(computing) browser (software)
browser m (plural browseres)
browser | 31 |
338 | browser | Browser (wikipedia) | Browse, browser or browsing may refer to:
== Programs ==
Web browser, a program used to access the World Wide Web
Code browser, a program for navigating source code
File browser or file manager, a program used to manage files and related objects
Hardware browser, a program for displaying networked hardware devices
Image browser or image viewer, a program that can display stored graphical images
Browser service, a feature of Microsoft Windows to browse shared network resources
== Other ==
Browsing, a kind of orienting strategy in animals and human beings
Browsing (herbivory), a type of feeding behavior in herbivores
Browse Island, Australia
Browse LNG, Australian liquefied natural gas plant project
Browser (cat), a Texan library cat | Browse, browser or browsing may refer to: | 0 |
339 | browser | Browser (cat) (wikipedia) | Browser is an American library cat that lives in White Settlement Public Library, near Fort Worth, Texas, United States. He is a grey tabby cat. In July 2016, Browser was evicted from the library by the local municipality, provoking an international backlash that resulted in a re-vote, and a unanimous decision permitting him to stay.
== Eviction attempt ==
Browser was adopted by White Settlement Public Library from a local animal shelter in October 2010. Originally he was obtained to control rodents, but later became a popular mascot of the library among patrons, even featuring in the library's fundraising calendar.
On June 14, 2016, White Settlement City Council voted by a majority of two to one votes to remove Browser from the library. The removal motion was made by councillor Elzie Clements, who claimed, “City Hall and City businesses are no place for animals”, and council member Paul Moore, who was primarily concerned about triggering people with allergies to cats. Mayor Ron White claimed that the motion to remove Browser was a response to a council worker not being permitted to bring his puppy to City Hall.
== Later developments ==
In response to the eviction decision, a petition to permit Browser to remain in the library attracted over 12,000 signatures worldwide, and Mayor White received over 1,500 emails advocating for Browser to be permitted to remain in the library. On July 1, 2016, White Settlement City Council unanimously voted to reverse its earlier eviction decision.
Browser was subsequently dubbed by the mayor as "Library Cat for Life".
Browser was featured in the library's yearly calendar as a fundraiser, effectively bringing in more money than he cost.
On December 13, 2016, Clements again tried to bring the council to vote to remove Browser, claiming “I’m a council member and I can put anything I want on the consent agenda”, but the motion did not pass. This would be the last meeting attended by Councilman Clements as an elected official. Clements was defeated in his council re-election bid in 2016, and died on January 1, 2022.
== See also ==
List of individual cats
== References ==
== External links ==
White Settlement Public Library | Browser is an American library cat that lives in White Settlement Public Library, near Fort Worth, Texas, United States. He is a grey tabby cat. In July 2016, Browser was evicted from the library by the local municipality, provoking an international backlash that resulted in a re-vote, and a unanimous decision permitting him to stay. | 2 |
340 | browser | Browsing (herbivory) (wikipedia) | Browsing is a type of herbivory in which a herbivore (or, more narrowly defined, a folivore) feeds on leaves, soft shoots, or fruits of high-growing, generally woody plants such as shrubs. This is contrasted with grazing, usually associated with animals feeding on grass or other lower vegetations. Alternatively, grazers are animals eating mainly grass, and browsers are animals eating mainly non-grasses, which include both woody and herbaceous dicots. In either case, an example of this dichotomy are goats (which are primarily browsers) and sheep (which are primarily grazers).
== Browse ==
The plant material eaten is known as browse and is in nature taken directly from the plant, though owners of livestock such as goats and deer may cut twigs or branches for feeding to their stock. In temperate regions, owners take browse before leaf fall, then dry and store it as a winter feed supplement. In time of drought, herdsmen may cut branches from beyond the reach of their stock, as forage at ground level. In the tropical regions, where population pressure leads owners to resort to this more often, there is a danger of permanent depletion of the supply. Animals in captivity may be fed browse as a replacement for their wild food sources; in the case of pandas, the browse may consist of bunches of banana leaves, bamboo shoots, slender pine, spruce, fir and willow branches, straw and native grasses.
If the population of browsers grows too high, all of the browse that they can reach may be devoured. The resulting level below which few or no leaves are found is known as the browse line. If over-browsing continues for too long, the ability of the ecosystem's trees to reproduce may be impaired, as young plants cannot survive long enough to grow too tall for browsers to reach.
== Overbrowsing ==
Overbrowsing occurs when overpopulated or densely-concentrated herbivores exert extreme pressure on plants, reducing the carrying capacity and altering the ecological functions of their habitat. Examples of overbrowsing herbivores around the world include koalas in Southern Australia, introduced mammals in New Zealand, and cervids in forests of North America and Europe.
=== Overview ===
Moose exclosures (fenced-off areas) are used to determine the ecological impacts of cervids, allowing scientists to compare flora, fauna, and soil in areas inside and outside of exclosures. Changes in plant communities in response to herbivory reflect the differential palatability of plants to the overabundant herbivore, as well as the variable ability of plants to tolerate high levels of browsing. The heights of plants preferred by herbivores can give indications of the local and regional herbivore density. Compositional and structural changes in forest vegetation can have cascading effects on the entire ecosystem, including impacts on soil quality and stability, micro- and macro- invertebrates, small mammals, songbirds, and perhaps even large predators.
=== Causes ===
There are several causes of overabundant herbivores and subsequent overbrowsing. Herbivores are introduced to landscapes in which native plants have not evolved to withstand browsing, and predators have not adapted to hunt the invading species. In other cases, populations of herbivores exceed historic levels due to reduced hunting or predation pressure. For example, carnivores declined in North America throughout the 19th century and hunting regulations became stricter, contributing to increased cervid populations across North America. Also, landscape changes due to human development, such as in agriculture and forestry, can produce fragmented forest patches between which deer travel, browsing in early successional habitat at the periphery. Agricultural fields and young silvicultural stands provide deer with high quality food leading to overabundance and increased browsing pressure on forest understory plants.
=== Impacts on plants ===
Overbrowsing impacts plants at individual, population, and community levels. The negative effects of browsing are greater among intolerant species, such as members of the genus Trillium, which have all photosynthetic tissues and reproductive organs at the apex of a singular stem. This means that a deer may eat all the reproductive and photosynthetic tissues at once, reducing the plant's height, photosynthetic capabilities, and reproductive output. This is one example of how overbrowsing can lead to the loss of reproductive individuals in a population, and a lack of recruitment of young plants. Plants also differ in their palatability to herbivores. At high densities of herbivores, plants that are highly selected as browse may be missing small and large individuals from the population. At the community level, intense browsing by deer in forests leads to reductions in the abundance of palatable understory herbaceous shrubs, and increases in graminoid and bryophyte abundance which are released from competition for light.
==== Browsing Pressure and Plant Palatability ====
The intensity of browsing pressure often varies depending on the palatability of plant species to herbivores. Some plant species may be heavily browsed due to their high palatability, while others may be avoided or less affected.
==== Effects on Plant Reproduction ====
Browsing can affect plant reproduction by reducing the availability of leaves for photosynthesis and flowers for pollination. Overbrowsing can lead to a decrease in seed production, hinder the recruitment of new individuals and alter the genetic diversity of plant population.
=== Impacts on other animals ===
Overbrowsing can change near-ground forest structure, plant species composition, vegetation density, and leaf litter, with consequences for other forest-dwelling animals. Many species of ground-dwelling invertebrates rely on near-ground vegetation cover and leaf litter layers for habitat; these invertebrates may be lost from areas with intense browsing. Further, preferential selection of certain plant species by herbivores can impact invertebrates closely associated with those plants. Migratory forest-dwelling songbirds depend on dense understory vegetation for nesting and foraging habitat; reductions in understory plant biomass caused by deer can lead to declines in forest songbird populations. Finally, loss of understory plant diversity associated with ungulate overbrowsing can impact small mammals that rely on this vegetation for cover and food.
=== Management and recovery ===
Overbrowsing can lead plant communities towards equilibrium states which are only reversible if herbivore numbers are greatly reduced for a sufficient period, and actions are taken to restore the original plant communities. Management to reduce deer populations has a three-method approach: (1) large areas of contiguous old forest with closed canopies are set aside, (2) predator populations are increased, and (3) hunting of the overabundant herbivore is increased. Encouragement of tree recovery by promoting seed sources of native trees is an important aspect of managing recovery from overbrowsing. Refugia in the form of windthrow mounds, rocky outcrops, or horizontal logs elevated above the forest floor can provide plants with substrate protected from browsing by cervids. These refugia can contain a proportion of the plant community that would exist without browsing pressure, and may differ significantly from the flora found in nearby browsed areas. If management efforts were to reduce cervid populations in the landscape, these refugia could serve as a model for understory recovery in the surrounding plant community.
== See also ==
Consumer–resource interactions
Silvopasture
Tree shelter
Yellow-cedar decline
== References == | Browsing is a type of herbivory in which a herbivore (or, more narrowly defined, a folivore) feeds on leaves, soft shoots, or fruits of high-growing, generally woody plants such as shrubs. This is contrasted with grazing, usually associated with animals feeding on grass or other lower vegetations. Alternatively, grazers are animals eating mainly grass, and browsers are animals eating mainly non-grasses, which include both woody and herbaceous dicots. In either case, an example of this dichotomy are goats (which are primarily browsers) and sheep (which are primarily grazers). | 3 |
341 | browser | DR-WebSpyder (wikipedia) | DR-WebSpyder is a DOS web browser, mail client and operating system runtime environment that was developed by Caldera UK in 1997. It was based on the DR-DOS operating system and networking components from Novell as well as the Arachne web browser by Michal Polák of xChaos software. The system was designed to run on low-end desktop systems, but being able to boot and execute from disk as well as from ROM or network, it was also tailored for x86-based thin clients and embedded systems with or without disk drives. Using the web browser as its principal user interface, it could be also used for kiosk systems and set-top boxes. It was ported to Linux in 1999 under the name Embrowser and was renamed Embedix Browser in 2000.
== NIOS and IOS ==
DR-WebSpyder was originally conceived as project NIOS (Novell Internet Operating System) at Novell's European Development Centre (EDC), UK in 1994 by then DR-DOS engineer Roger Alan Gross, who was working on Novell's Embedded Systems Technology (NEST) initiative to create embedded system applications that connect intelligent devices to NetWare networks. NIOS was conceived as a thin client operating system that provided Novell with a graphical client operating system to run web applications hosted on NetWare, creating a Novell-centric platform for software as a service (SaaS) that did not require Microsoft's Windows operating system. NIOS comprised 32-bit versions of Novell's existing 16-bit DOS technologies including the DR-DOS operating system, Novell's modem dialer and TCP/IP stack from LAN Workplace for DOS / NetWare Mobile plus licensed third-party components such as the Kaffe Java virtual machine (JVM), Allegro for graphics, and Mosaic for the web browser.
== WebSpyder, WebSpyder 32 and DR-WebSpyder ==
Gross's plans were interrupted when Caldera, Inc. acquired the remaining Digital Research assets including DR-DOS from Novell on 23 July 1996, but without the personnel. Gross telephoned Caldera's Ransom H. Love the same day offering to set up a new DR-DOS team outside of Novell. Gross subsequently joined Caldera as general manager of the Digital Research Systems Group (DSG) in December that year and set about rehiring the DRDOS/NIOS team in the UK to develop the new operating system and web browser. Under Caldera, NIOS was renamed IOS (Internet Operating System). The plan to use Mosaic was also dropped and instead Caldera licensed the source code of the 16-bit DOS web browser Arachne. The team replaced Arachne's dialer and packet drivers with Novell's dialer, ODI driver suite (from Personal NetWare etc.) and TCP/IP stack, added support for animated and scaled GIFs, an optional on-screen keyboard for mouse and touch panel usage (SoftKeyboards) for possible keyboardless operation, and an install program. Also, they completely changed the design of the browser (customizable chrome), implemented support for NetScape-compatible frames, and used Allegro for graphics. The browser also supported "execute links" to run and interact with DOS programs and batchjobs run on the web client, a feature originally introduced as DOS Gateway Interface (DGI) in Arachne. IOS became formally known as WebSpyder in May 1997. Some months later, it was ported to compile as a 32-bit protected mode extended DOS application (utilizing DPMI using DJGPP, a GNU compiler for DOS), then referred to as WebSpyder 32, but renamed DR-WebSpyder in early 1998.
On 11 May 1998, Caldera started shipping DR-WebSpyder 2.0 as both a HTML 3.2 web browser application and browser OS. On 1 June 1998, the company opened a sales and support office in Taiwan to be close to potential OEM customers.
A maintenance release DR-WebSpyder 2.0a was issued on 19 August 1998.
Caldera distributed a free demo version of DR-WebSpyder 2.0a on a self-booting disk. This was in fact the DR-WebSpyder OS configured as loosely coupled components in which a special version of the DR-DOS ANSI.SYS driver would mute the stream of text messages at startup of the DOS system while a graphical company logo was displayed until the web browser was launched as a shell via CONFIG.SYS SHELL replacing the default COMMAND.COM command line interpreter. On 386 PCs with a minimum of 4 MB of RAM, the floppy would boot the DR-DOS 7.02 based browser operating system complete with memory manager, RAM disk, dial-up modem, LAN, mouse and display drivers and automatically launch into the graphical browser, without ever touching the machine's hard disk in order not to interfere with other systems installed on the machine and to demonstrate its potential usage in diskless workstations. Users could start browsing the web or accessing mails immediately after entering their access credentials. A further refined international revision of the demo by Matthias R. Paul utilized more sophisticated multi-level compression to free enough space on the floppy image to also include menu options and additional drivers to choose between several languages and keyboard layouts and give room for further expansion or customization of the operation system and browser through OEMs or users.
On 2 September 1998, it was announced that the Digital Research Systems Group and consequently also Caldera UK was spun out as a separate company Caldera Thin Clients (CTC), incorporated earlier in August 1998.
In September 1998, DR-WebSpyder 2.0 achieved commercial success when it was selected for use in an internet set-top box as part of a satellite internet access solution.
On 3 November 1998, the company announced DR-WebSpyder 2.1. With DR-WebSpyder 2.1 Beta 2 being available since 7 November 1998, the browser was released on 30 November 1998. It added support for JavaScript, the Secure Sockets Layer (SSL) protocol, cookies, sound files, printing on a multitude of printers as well as user profiles and support for multiple mail accounts. It also added scrollable quarter-screen VGA support for low-resolution LCD displays as well as anti-aliased fonts for display on TVs in an optional TV interface mode.
Caldera UK also investigated possibilities to add Java and JVM support to the browser, but this component never left prototype status. Two desired prerequisites for Java integration were to add support for long filenames (LFNs) and Unicode to DOS. Caldera's DPMS-enabled dynamically loadable LONGNAME driver provided VFAT-compatible LFNs in the FAT file system utilizing UCS-2 internally. Matthias R. Paul conducted research how to achieve this with minimal changes to the existing system and to not cause bloat to an operating system also tailored for thin clients and embedded systems. Expanded DRFONT-style .CPI files could have been provided to retrieve bitmaps for the required larger character repertoire (Basic Multilingual Plane or Windows Glyph List 4) not only to support a lot more code pages in general, but also wider character sets similar to what was used in DOS/V-compatible systems. In conjunction with a new COUNTRY.SYS file, Paul's enhanced NLSFUNC 4.xx driver, which was introduced with DR-DOS 7.02, could have provided the framework to integrate optional UTF-8 support into the system in a way similar to DBCS support.
When Gross resigned in January 1999, Caldera Thin Clients, Inc. closed the Caldera UK Ltd. development office in February 1999 soon after the release of DR-DOS 7.03.
== Embrowser and Embedix Browser ==
On 20 July 1999, Caldera Thin Clients renamed itself into Lineo under the new lead of Bryan Wayne Sparks. DR-WebSpyder was renamed Embrowser and the browser was said to be ported to Linux.
A version of DR-WebSpyder for IMS REAL/32, a successor to Digital Research's and Novell's Multiuser DOS, has been worked on in 1999 as well.
Since October 1999, a DOS version of DR-WebSpyder 2.5 aka Embrowser 2.5 was available on Lineo's site.
Since Lineo's own thin-client Linux distribution was named Embedix, the Linux port of the micro web browser was consequently named Embedix Browser by April 2000.
In April 2002, some Lineo assets were auctioned off and the company reformed as Embedix, Inc. by July 2002 under the lead of Matthew R. Harris. Motorola's Metrowerks bought Embedix key assets, possibly including the browser, on 17 December 2002.
== Features ==
== See also ==
Arachne (web browser)
Citrix WinFrame
ChromeOS
DR-DOS
FreeDOS
Comparison of web browsers
List of web browsers
LAN WorkPlace for DOS
Caldera View
iCentrix MarioNet
Novell Corsair
WebTV
== Notes ==
== References ==
== Further reading ==
"Caldera WebSpyder 32 User Guide - BETA 1 Draft". Caldera, Inc. 1998-02-05. Archived from the original on 1998-02-05. Retrieved 2019-07-14.
== External links ==
Caldera, Inc. (archived web site caldera.com from 1996-10-18 to 1999-04-30)
Caldera UK Ltd. (archived web site caldera.co.uk from 1997-12-21 to 1999-10-12)
Caldera Thin Clients, Inc. (archived web site calderathin.com from 1999-01-17 to 1999-11-05) and Lineo, Inc. (archived web site calderathin.com from 1999-10-12 to 1999-11-05, lineo.com from 2000-05-10 to 2003-03-20 and embedix.com from 2002-06-03 to 2003-02-20) | DR-WebSpyder is a DOS web browser, mail client and operating system runtime environment that was developed by Caldera UK in 1997. It was based on the DR-DOS operating system and networking components from Novell as well as the Arachne web browser by Michal Polák of xChaos software. The system was designed to run on low-end desktop systems, but being able to boot and execute from disk as well as from ROM or network, it was also tailored for x86-based thin clients and embedded systems with or without disk drives. Using the web browser as its principal user interface, it could be also used for kiosk systems and set-top boxes. It was ported to Linux in 1999 under the name Embrowser and was renamed Embedix Browser in 2000.
| 4 |
342 | browser | Web browser (wikipedia) | A web browser is an application for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used on a range of devices, including desktops, laptops, tablets, and smartphones. In 2020, an estimated 4.9 billion people have used a browser. The most-used browser is Google Chrome, with a 64% global market share on all devices, followed by Safari with 19%.
A web browser is not the same thing as a search engine, though the two are often confused. A search engine is a website that provides links to other websites. However, to connect to a website's server and display its web pages, a user must have a web browser installed. In some technical contexts, browsers are referred to as user agents.
== Function ==
The purpose of a web browser is to fetch content from the Web or local storage and display it on the user's device. This process begins when the user inputs a Uniform Resource Locator (URL), such as https://en.wikipedia.org/, into the browser. Virtually all URLs on the Web start with either http: or https: which means they are retrieved with the Hypertext Transfer Protocol (HTTP). For secure mode (HTTPS), the connection between the browser and web server is encrypted, providing a secure and private data transfer.
Web pages usually contain hyperlinks to other pages and resources. Each link contains a URL, and when it is clicked or tapped, the browser navigates to the new resource. Most browsers use an internal cache of web page resources to improve loading times for subsequent visits to the same page. The cache can store many items, such as large images, so they do not need to be downloaded from the server again. Cached items are usually only stored for as long as the web server stipulates in its HTTP response messages.
=== Privacy ===
During the course of browsing, cookies received from various websites are stored by the browser. Some of them contain login credentials or site preferences. However, others are used for tracking user behavior over long periods of time, so browsers typically provide a section in the menu for deleting cookies. Finer-grained management of cookies usually requires a browser extension.
== History ==
The first web browser, called WorldWideWeb, was created in 1990 by Sir Tim Berners-Lee. He then recruited Nicola Pellow to write the Line Mode Browser, which displayed web pages on dumb terminals. The Mosaic web browser was released in April 1993, and was later credited as the first web browser to find mainstream popularity. Its innovative graphical user interface made the World Wide Web easy to navigate and thus more accessible to the average person. This, in turn, sparked the Internet boom of the 1990s, when the Web grew at a very rapid rate. The lead developers of Mosaic then founded the Netscape corporation, which released the Mosaic-influenced Netscape Navigator in 1994. Navigator quickly became the most popular browser.
Microsoft debuted Internet Explorer in 1995, leading to a browser war with Netscape. Within a few years, Microsoft gained a dominant position in the browser market for two reasons: it bundled Internet Explorer with its popular Windows operating system and did so as freeware with no restrictions on usage. The market share of Internet Explorer peaked at over 95% in the early 2000s. In 1998, Netscape launched what would become the Mozilla Foundation to create a new browser using the open-source software model. This work evolved into the Firefox browser, first released by Mozilla in 2004. Firefox's market share peaked at 32% in 2010. Apple released its Safari browser in 2003; it remains the dominant browser on Apple devices, though it did not become popular elsewhere.
Google debuted its Chrome browser in 2008, which steadily took market share from Internet Explorer and became the most popular browser in 2012. Chrome has remained dominant ever since. By 2015, Microsoft replaced Internet Explorer with Edge for the Windows 10 release.
Since the early 2000s, browsers have greatly expanded their HTML, CSS, JavaScript, and multimedia capabilities. One reason has been to enable more sophisticated websites, such as web apps. Another factor is the significant increase of broadband connectivity in many parts of the world, enabling people to access data-intensive content, such as streaming HD video on YouTube, that was not possible during the era of dial-up modems.
== Browser market ==
Google Chrome has been the dominant browser since the mid-2010s and currently has a 64% global market share on all devices. The vast majority of its source code comes from Google's open-source Chromium project; this code is also the basis for many other browsers, including Microsoft Edge, currently in third place with about a 5% share, and Opera and Samsung Internet in fifth and sixth place with over 2% each.
The other two browsers in the top four are made from different codebases. Safari, based on Apple's WebKit code, is dominant on Apple devices, resulting in a 19% global share. Firefox, with about a 3% share, is based on Mozilla's code. Both of these codebases are open-source, so a number of small niche browsers are also made from them.
== Features ==
The most popular browsers share many features in common. They automatically log users' browsing history, unless the users turn off their browsing history or use the non-logging private mode. They also allow users to set bookmarks, customize the browser with extensions, and can manage user passwords. Some provide a sync service and web accessibility features.
Common user interface (UI) features:
Allowing the user to have multiple pages open at the same time, either in different browser windows or in different tabs of the same window.
Back and forward buttons to go back to the previous page visited or forward to the next one.
A refresh or reload and a stop button to reload and cancel loading the current page. (In most browsers, the stop button is merged with the reload button.)
A home button to return to the user's home page.
An address bar to input the URL of a page and display it, and a search bar to input queries into a search engine. (In most browsers, the search bar is merged with the address bar.)
While mobile browsers have similar UI features as desktop versions, the limitations of touch screens require mobile UIs to be simpler. The difference is significant for users accustomed to keyboard shortcuts. The most popular desktop browsers also have sophisticated web development tools.
== Security ==
Web browsers are popular targets for hackers, who exploit security holes to steal information, destroy files, and other malicious activities. Browser vendors regularly patch these security holes, so users are strongly encouraged to keep their browser software updated. Other protection measures are antivirus software and being aware of scams.
== See also ==
Comparison of web browsers
History of the World Wide Web
Timeline of web browsers
== References ==
== External links ==
Media related to Web browsers at Wikimedia Commons | A web browser is an application for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used on a range of devices, including desktops, laptops, tablets, and smartphones. In 2020, an estimated 4.9 billion people have used a browser. The most-used browser is Google Chrome, with a 64% global market share on all devices, followed by Safari with 19%.
A web browser is not the same thing as a search engine, though the two are often confused. A search engine is a website that provides links to other websites. However, to connect to a website's server and display its web pages, a user must have a web browser installed. In some technical contexts, browsers are referred to as user agents. | 8 |
343 | mac | Macintosh (wiktionary) | These are all alternative forms of the surname, not the computer brand:
MacIntosh
Mackintosh
McIntosh
From Scottish Gaelic Mac-an-tòisich, meaning "son of the thane (Old Irish toísech (“leader”))".
Macintosh (plural Macintoshes)
A Scottish surname from Scottish Gaelic.
Macintosh (plural Macintoshes)
(computing) A brand of personal computer manufactured by Apple Inc.
Mac
Machead
eMac
Hackintosh
iMac
MacBook
monachist
Borrowed from English Macintosh.
IPA(key): /ma.kin.tɔʃ/
Macintosh m
(computing) Macintosh
mac
Borrowed from English Macintosh.
IPA(key): /maˈkin.tɔʂ/
Rhymes: -intɔʂ
Syllabification: Ma‧cin‧tosh
Macintosh m
(computing) Macintosh (brand)
macintosh
Macintosh in Polish dictionaries at PWN | These are all alternative forms of the surname, not the computer brand:
MacIntosh
Mackintosh
McIntosh
From Scottish Gaelic Mac-an-tòisich, meaning "son of the thane (Old Irish toísech (“leader”))".
Macintosh (plural Macintoshes)
A Scottish surname from Scottish Gaelic.
Macintosh (plural Macintoshes)
(computing) A brand of personal computer manufactured by Apple Inc.
Mac
Machead
eMac
Hackintosh
iMac
MacBook
monachist
Borrowed from English Macintosh.
IPA(key): /ma.kin.tɔʃ/
Macintosh m
(computing) Macintosh
mac
Borrowed from English Macintosh.
IPA(key): /maˈkin.tɔʂ/
Rhymes: -intɔʂ
Syllabification: Ma‧cin‧tosh
Macintosh m
(computing) Macintosh (brand)
macintosh
Macintosh in Polish dictionaries at PWN | 21 |
344 | mac | macintosh (wiktionary) | macintosh (plural macintoshes)
(British) Alternative form of mackintosh (“a raincoat”)
monachist
IPA(key): /maˈkin.tɔʂ/
Rhymes: -intɔʂ
Syllabification: ma‧cin‧tosh
macintosh m animal
a Macintosh computer
macintosh in Polish dictionaries at PWN | macintosh (plural macintoshes)
(British) Alternative form of mackintosh (“a raincoat”)
monachist
IPA(key): /maˈkin.tɔʂ/
Rhymes: -intɔʂ
Syllabification: ma‧cin‧tosh
macintosh m animal
a Macintosh computer
macintosh in Polish dictionaries at PWN | 7 |
345 | mac | mac (wiktionary) | mac
(international standards) ISO 639-2/B language code for Macedonian.
enPR: măk, IPA(key): /mæk/
Rhymes: -æk
Homophones: Mac, mack, Mack
Clipping of mackintosh.
mac (plural macs)
Clipping of mackintosh (“a raincoat”).
pac-a-mac
Clipping of macaroni.
mac (uncountable)
(Canada, US, slang) Clipping of macaroni.
mac and cheese, mac 'n' cheese
mac salad
ACM, AMC, C.M.A., CAM, CMA, Cam, MCA, cam
Uncertain.
IPA(key): (Central, Balearic, Valencia) [ˈmak]
mac m (plural macs)
(balearic) small stone, pebble
Synonym: còdol
mac de torrent
macar
“mac” in Diccionari de la llengua catalana, segona edició, Institut d’Estudis Catalans.
IPA(key): /mak/
mac m (plural macs)
(colloquial, slang) Clipping of maquereau (“pimp”).
mac m (plural macs)
(colloquial, computing) Clipping of Macintosh.
“mac”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.
From Old Irish macc, from Primitive Irish ᚋᚐᚊᚊᚔ (maqqi, genitive), from Proto-Celtic *makkʷos, a variant of *makʷos (“son”) (compare Welsh mab, Gaulish mapos, Maponos).
(Munster, Aran) IPA(key): /mˠɑk/
(Cois Fharraige) IPA(key): /mˠaːk/
(Mayo, Ulster) IPA(key): /mˠak/
mac m (genitive singular mic, nominative plural mic)
son
A common prefix of many Irish and Scottish names, signifying "son of".
Dónall óg donn Mac Lochlainn ― young, brown-haired Donald, son of the Scandinavian
iníon (“daughter”)
Ó Dónaill, Niall (1977) “mac”, in Foclóir Gaeilge–Béarla, Dublin: An Gúm, →ISBN
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 mac, macc”, in eDIL: Electronic Dictionary of the Irish Language
Sjoestedt, M. L. (1931) Phonétique d’un parler irlandais de Kerry (in French), Paris: Librairie Ernest Leroux, page 57
mac
(Classical K'iche') sin
Inherited from Proto-Slavic *mati.
IPA(key): /ˈmat͡s/
Rhymes: -at͡s
Syllabification: mac
mac f
mother
Eùgeniusz Gòłąbk (2011) “macierz”, in Słownik Polsko-Kaszubski / Słowôrz Pòlskò-Kaszëbsczi[2]
“mac”, in Internetowi Słowôrz Kaszëbsczégò Jãzëka [Internet Dictionary of the Kashubian Language], Fundacja Kaszuby, 2022
From Old Irish macc, from Primitive Irish ᚋᚐᚊᚊᚔ (maqqi, genitive), from Proto-Celtic *makkʷos, a variant of *makʷos (“son”), from Proto-Indo-European *meh₂ḱ- (“to raise, increase”).
mac m (genitive singular mic, plural mec)
son
mac-
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 mac, macc”, in eDIL: Electronic Dictionary of the Irish Language
mac
Alternative form of make (“equal, partner”)
IPA(key): /mak/
From Old Irish macc, from Primitive Irish ᚋᚐᚊᚊᚔ (maqqi, genitive), from Proto-Celtic *makkʷos, a variant of *makʷos (“son”), from Proto-Indo-European *meh₂ḱ- (“to raise, increase”).
mac m (genitive mic, nominative plural mic)
son
Irish: mac
Manx: mac
Scottish Gaelic: mac
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 mac, macc”, in eDIL: Electronic Dictionary of the Irish Language
From Proto-Celtic *makkos. Cognate with Welsh mach.
mac m
bond, surety
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “2 mac(c)”, in eDIL: Electronic Dictionary of the Irish Language
mac m (genitive maic or meic, nominative plural maic or meic)
Alternative spelling of macc (“son, child”)
IPA(key): /mak/
Borrowed from Old Church Slavonic макъ (makŭ), from Proto-Slavic *makъ (“poppy”). Compare Serbo-Croatian mak, Polish mak.
mac m (plural maci)
poppy
Onomatopoeic.
mac
quack (sound made by ducks)
From Middle Irish mac, from Old Irish macc, from Primitive Irish ᚋᚐᚊᚊᚔ (maqqi, genitive), from Proto-Celtic *makkʷos. Cognates include Irish mac and Manx mac.
IPA(key): /maʰk/, [maxk]
Hyphenation: mac
mac m (genitive singular mic, plural mic)
son
Used as a prefix for Irish and Scottish patronymic surnames; -son
mac Dhòmhaill ― MacDonald (literally, “son of Donald”)
Edward Dwelly (1911) “mac”, in Faclair Gàidhlig gu Beurla le Dealbhan [The Illustrated Gaelic–English Dictionary][3], 10th edition, Edinburgh: Birlinn Limited, →ISBN
Colin Mark (2003) “mac”, in The Gaelic-English dictionary, London: Routledge, →ISBN, page 411
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 mac, macc”, in eDIL: Electronic Dictionary of the Irish Language
Inherited from Proto-Slavic *màti.
IPA(key): /ˈmat͡s/
Rhymes: -at͡s
Syllabification: mac
mac f
mother (human female who begets a child)
Lorentz, Friedrich (1908) “mãc”, in Slovinzisches Wörterbuch[4] (in German), volume 1, Saint Petersburg: ОРЯС ИАН, page 595
Cognate with Jumjum maañ, Belanda Bor mac, Shilluk mac.
mac (plural mɛ̈c)
fire
light firearm
prison
Dinka-English Dictionary[5], 2005 | mac
(international standards) ISO 639-2/B language code for Macedonian.
enPR: măk, IPA(key): /mæk/
Rhymes: -æk
Homophones: Mac, mack, Mack
Clipping of mackintosh.
mac (plural macs)
Clipping of mackintosh (“a raincoat”).
pac-a-mac
Clipping of macaroni.
mac (uncountable)
(Canada, US, slang) Clipping of macaroni.
mac and cheese, mac 'n' cheese
mac salad
ACM, AMC, C.M.A., CAM, CMA, Cam, MCA, cam
Uncertain.
IPA(key): (Central, Balearic, Valencia) [ˈmak]
mac m (plural macs)
(balearic) small stone, pebble
Synonym: còdol
mac de torrent
macar
“mac” in Diccionari de la llengua catalana, segona edició, Institut d’Estudis Catalans.
IPA(key): /mak/
mac m (plural macs)
(colloquial, slang) Clipping of maquereau (“pimp”).
mac m (plural macs)
(colloquial, computing) Clipping of Macintosh.
“mac”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.
From Old Irish macc, from Primitive Irish ᚋᚐᚊᚊᚔ (maqqi, genitive), from Proto-Celtic *makkʷos, a variant of *makʷos (“son”) (compare Welsh mab, Gaulish mapos, Maponos).
(Munster, Aran) IPA(key): /mˠɑk/
(Cois Fharraige) IPA(key): /mˠaːk/
(Mayo, Ulster) IPA(key): /mˠak/
mac m (genitive singular mic, nominative plural mic)
son
A common prefix of many Irish and Scottish names, signifying "son of".
Dónall óg donn Mac Lochlainn ― young, brown-haired Donald, son of the Scandinavian
iníon (“daughter”)
Ó Dónaill, Niall (1977) “mac”, in Foclóir Gaeilge–Béarla, Dublin: An Gúm, →ISBN
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 mac, macc”, in eDIL: Electronic Dictionary of the Irish Language
Sjoestedt, M. L. (1931) Phonétique d’un parler irlandais de Kerry (in French), Paris: Librairie Ernest Leroux, page 57
mac
(Classical K'iche') sin
Inherited from Proto-Slavic *mati.
IPA(key): /ˈmat͡s/
Rhymes: -at͡s
Syllabification: mac
mac f
mother
Eùgeniusz Gòłąbk (2011) “macierz”, in Słownik Polsko-Kaszubski / Słowôrz Pòlskò-Kaszëbsczi[2]
“mac”, in Internetowi Słowôrz Kaszëbsczégò Jãzëka [Internet Dictionary of the Kashubian Language], Fundacja Kaszuby, 2022
From Old Irish macc, from Primitive Irish ᚋᚐᚊᚊᚔ (maqqi, genitive), from Proto-Celtic *makkʷos, a variant of *makʷos (“son”), from Proto-Indo-European *meh₂ḱ- (“to raise, increase”).
mac m (genitive singular mic, plural mec)
son
mac-
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 mac, macc”, in eDIL: Electronic Dictionary of the Irish Language
mac
Alternative form of make (“equal, partner”)
IPA(key): /mak/
From Old Irish macc, from Primitive Irish ᚋᚐᚊᚊᚔ (maqqi, genitive), from Proto-Celtic *makkʷos, a variant of *makʷos (“son”), from Proto-Indo-European *meh₂ḱ- (“to raise, increase”).
mac m (genitive mic, nominative plural mic)
son
Irish: mac
Manx: mac
Scottish Gaelic: mac
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 mac, macc”, in eDIL: Electronic Dictionary of the Irish Language
From Proto-Celtic *makkos. Cognate with Welsh mach.
mac m
bond, surety
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “2 mac(c)”, in eDIL: Electronic Dictionary of the Irish Language
mac m (genitive maic or meic, nominative plural maic or meic)
Alternative spelling of macc (“son, child”)
IPA(key): /mak/
Borrowed from Old Church Slavonic макъ (makŭ), from Proto-Slavic *makъ (“poppy”). Compare Serbo-Croatian mak, Polish mak.
mac m (plural maci)
poppy
Onomatopoeic.
mac
quack (sound made by ducks)
From Middle Irish mac, from Old Irish macc, from Primitive Irish ᚋᚐᚊᚊᚔ (maqqi, genitive), from Proto-Celtic *makkʷos. Cognates include Irish mac and Manx mac.
IPA(key): /maʰk/, [maxk]
Hyphenation: mac
mac m (genitive singular mic, plural mic)
son
Used as a prefix for Irish and Scottish patronymic surnames; -son
mac Dhòmhaill ― MacDonald (literally, “son of Donald”)
Edward Dwelly (1911) “mac”, in Faclair Gàidhlig gu Beurla le Dealbhan [The Illustrated Gaelic–English Dictionary][3], 10th edition, Edinburgh: Birlinn Limited, →ISBN
Colin Mark (2003) “mac”, in The Gaelic-English dictionary, London: Routledge, →ISBN, page 411
Gregory Toner, Sharon Arbuthnot, Máire Ní Mhaonaigh, Marie-Luise Theuerkauf, Dagmar Wodtko, editors (2019), “1 mac, macc”, in eDIL: Electronic Dictionary of the Irish Language
Inherited from Proto-Slavic *màti.
IPA(key): /ˈmat͡s/
Rhymes: -at͡s
Syllabification: mac
mac f
mother (human female who begets a child)
Lorentz, Friedrich (1908) “mãc”, in Slovinzisches Wörterbuch[4] (in German), volume 1, Saint Petersburg: ОРЯС ИАН, page 595
Cognate with Jumjum maañ, Belanda Bor mac, Shilluk mac.
mac (plural mɛ̈c)
fire
light firearm
prison
Dinka-English Dictionary[5], 2005 | 94 |
346 | mac | Mac (wikipedia) | Mac or MAC may refer to:
== Common meanings ==
Mac (computer), a line of personal computers made by Apple Inc.
Mackintosh, a raincoat made of rubberized cloth
Mac, a prefix to surnames derived from Gaelic languages
McIntosh (apple), a Canadian apple cultivar
== Arts and entertainment ==
=== Fictional entities ===
Mac (Green Wing), a television character
Mac (It's Always Sunny in Philadelphia), a television character
Mac Gargan, an enemy of Spider-Man
Mac, a character on Foster's Home for Imaginary Friends
Angus "Mac" MacGyver, from the television series MacGyver
Cindy "Mac" Mackenzie, from the TV series Veronica Mars
Lt. Col. Sarah MacKenzie, from the TV series JAG
Dr. Terrence McAfferty, from Robert Muchamore's CHERUB and Henderson's Boys novel series
Mac McAnnally, in The Dresden Files series
Randle McMurphy, in the movie One Flew Over the Cuckoo's Nest
Mac Taylor, from the TV series CSI: NY
Mac, a canine character in the television series Clifford the Big Red Dog
Monster Attack Crew, a fictional pilot squadron in the television series Ultraman Leo
MAC (Mysterious Alien Creature), the titular character in the 1988 film Mac and Me
Mac (Makrand Deendayal Chatpatiya), portrayed by Akshay Kumar in the 2005 Indian comedy film Garam Masala
=== Other uses in arts and entertainment ===
Mac (film), 1992, directed by and starring John Turturro
Mac (novel), by John MacLean
Mac the Moose, a public statue in Moose Jaw, Saskatchewan, Canada; formerly the World's Largest Moose
Mac, a Sports Beanie Baby cardinal produced by Ty, Inc. in 1999
MAC Awards, for achievements in cabaret, comedy, and jazz, administered by the Manhattan Association of Cabarets & Clubs
== Business and economics ==
=== Business terminology ===
Marginal Abatement Cost, a concept in environmental economics
Material adverse change, a provision in mergers and acquisitions contracts and venture financing agreements
=== Businesses ===
MAC Cosmetics, a cosmetics brand, stylized as M•A•C
Mac Para Technology, a Czech aircraft manufacturer
Macerich, an American real estate investment trust (NYSE stock symbol MAC)
Manufacture d'armes de Châtellerault, a French state arms manufacturer
Martin's Air Charter, now Martinair, an airline
Medicare Administrative Contractor, a private company contracted to administer Medicare benefits in the U.S.
Military Armament Corporation, manufacturer of the MAC-10 and MAC-11 pistols
Morgan Advanced Ceramics, a ceramics manufacturing company
== Codes ==
MAC, the ISO 3166 code for Macau, a special administrative region of the People's Republic of China
MAC, Amtrac station code for Macomb (Amtrak station), Illinois, United States
mac, an ISO 639-2 code for the Macedonian language
== Organizations ==
=== Government and military agencies ===
Mainland Affairs Council, an agency under the Executive Yuan of the Republic of China
Metropolitan Airports Commission, the operator of airports in the Minneapolis-St. Paul area
Military Affairs Commission in China; see Central Military Commission (People's Republic of China)
Military Airlift Command, the predecessor of the Air Mobility Command of the United States Air Force
Municipal Assistance Corporation, created by the State of New York in 1975 to deal with New York City's fiscal crisis
=== Non-profit organizations ===
mac (Birmingham), formerly known as the Midlands Arts Centre, in Birmingham, UK
Malaysian AIDS Council
Marine Aquarium Council
Murphree Area Council
Myanmar Accountancy Council
=== Political groups ===
Mouvement d'Action Civique, a defunct Belgian far right group
Mouvement Autonome Casamançais (Casamancian Autonomous Movement), a defunct political party in Casamance, Senegal
Mudiad Amddiffyn Cymru, a Welsh organization responsible for several bombing incidents
Muslims Against Crusades, a UK-based Islamic group noted for burning poppies during the Remembrance Day silence in 2010
== People ==
=== Names ===
Mac (nickname)
Mạc, a Vietnamese surname
Mạc dynasty, 16th-century rulers in Vietnam
=== Individuals ===
Mac (rapper) (born 1977), American rapper, stage name of McKinley Phipps Jr
MC Mac, member and musician of So Solid Crew
John McCarthy (conductor) (1916–2009), British conductor known as "John Mac" or just "Mac"
Derek McCulloch (1897–1967), British radio broadcaster known as "Uncle Mac"
Ian McCulloch (singer) (born 1959), referred to as "Mac the Mouth" or just "Mac"
Stanley McMurtry (born 1936), British cartoonist with the pen name "Mac"
== Places ==
=== Museums and arts centers ===
mac, Birmingham (formerly Midlands Arts Centre), England
Metropolitan Arts Centre, Belfast, UK
Archaeology Museum of Catalonia (Spanish: Museu d'Arqueologia de Catalunya), Spain
Niterói Contemporary Art Museum (Portuguese: Museu de Arte Contemporânea de Niterói), Brazil
Museum of Contemporary Art of Lima (Spanish: Museo de Arte Contemporáneo), Peru
=== Other places ===
Macau, an administrative region of China (ISO 3166 code MAC)
Macaulay railway station, Melbourne, Australia
Macomb (Amtrak station), Illinois, United States, Amtrak station code MAC
UCLA Marina Aquatic Center, a recreational facility in Marina del Rey, California
== Schools ==
Macalester College in Saint Paul, Minnesota
Macdonald Campus of McGill University, Canada
McMaster University, in Canada
Michigan Agricultural College, former name of Michigan State University
== Science and technology ==
=== Biology and medicine ===
MAC (chemotherapy), a chemotherapy regimen of Mitoxantrone and Ara-C
Maximum allowable concentration, a concept related to threshold limit value (TLV)
Membrane attack complex, an immune system function using complement
Microbiota-accessible carbohydrates, a category of carbohydrates consumed by gut microbes
Minimum alveolar concentration, a measure used to compare the strengths of anesthetic vapors
Mitochondrial apoptosis-induced channel, the cytochrome c release pore of apoptotic mitochondria
Monitored anesthesia care, a form of anesthesia with partial awareness
Mycobacterium avium complex, a group of environmental pathogens
=== Computing and telecommunication ===
Mac (computer), a brand of computers and computer operating systems made by Apple Inc.
macOS, formerly Mac OS X and OS X, Apple's current operating system for Mac computers
Classic Mac OS, the original operating system for Apple's Macintosh
.Mac, now iCloud, a subscription service by Apple
MAC times, metadata containing event times associated with a computer file
Mandatory access control, a type of access control in computer security
Maximum activate count, a parameter associated with the LPDDR4 memory's TRR feature
Medium access control (or "Media Access Control"), a sublayer of the Data Link layer
MAC address, or Ethernet Hardware Address (EHA), the OSI layer 2 address of network interfaces
Message authentication code, used to authenticate a message in cryptography
Migration Authorisation Code, used when switching Internet service providers in the UK
Multiplexed Analogue Components, a proposed satellite television transmission standard
Multiply–accumulate operation (MAC), or multiplier–accumulator, in digital signal processing
.mac, a file extension for macros in Agilent ChemStation software
=== Transportation ===
Mean aerodynamic chord, a measure of the geometry of an airfoil
Merchant aircraft carrier, used during World War II by Britain and the Netherlands
Mid-air collision, a type of aircraft accident
=== Other uses in science and technology ===
Mission assurance category, an engineering designation used by the US Department of Defense
Money Access Card, an ATM (automated teller machine) card
== Sports ==
=== Clubs and teams ===
Maranhão Atlético Clube, a Brazilian association football club
Marília Atlético Clube, a Brazilian association football club
Missouri Athletic Club, a traditional gentlemen's and athletic club in downtown St. Louis, Missouri
Multnomah Athletic Club, a private athletic club in Oregon
=== Conferences ===
==== College ====
Mid-American Conference, an NCAA Division I (Football Bowl Subdivision) sports conference
Mid-Atlantic Rifle Conference, an NCAA rifle-only conference
Middle Atlantic Conferences, an umbrella organization for three NCAA Division III sports conferences
Middle Atlantic Conference, one of these three
==== High school ====
Macomb Area Conference, a Michigan high school football conference
Mayflower Athletic Conference, a Massachusetts high school athletic conference
Mid-Atlantic Athletic Conference, a Washington, D.C., area high school athletic league
Midwest Athletic Conference, an Ohio high school athletic conference in west-central Ohio
Mississippi Athletic Conference, an Iowa high school sports conference
Mountain Athletic Conference (NCHSAA), a North Carolina high school athletic conference
Mountain Athletic Conference (PIAA), a Pennsylvania high school athletic conference
=== Awards ===
MAC Award, now merged into the Hermann Trophy, the highest award in American college soccer
== Other uses ==
List of storms named Mac
Material adequacy condition, a concept in the philosophies of logic and language
Modern Army Combatives, a hand-to-hand combat training regimen
== See also ==
Macaroni and cheese, a dish often shortened to "mac and cheese"
Fort McMurray, Alberta, Canada, nicknamed "Fort Mac"
Big Mac (disambiguation)
Little Mac (disambiguation)
Mach (disambiguation)
Mack (disambiguation)
Mak (disambiguation) | Mac or MAC may refer to:
| 0 |
347 | mac | Mac (computer) (wikipedia) | Mac, short for Macintosh (its official name until 1999), is a family of personal computers designed and marketed by Apple. The name Macintosh is a reference to a type of apple called McIntosh. The product lineup includes the MacBook Air and MacBook Pro laptops, and the iMac, Mac Mini, Mac Studio, and Mac Pro desktops. Macs are sold with the macOS operating system.
Jef Raskin conceived the Macintosh project in 1979, which was usurped and redefined by Apple co-founder Steve Jobs in 1981. The Macintosh was launched in January 1984, after Apple's "1984" advertisement during Super Bowl XVIII. The system has a 9-inch monochrome monitor and 3 1/2-inch floppy drive built into the case and shipped with a one-button mouse. A series of incrementally improved models followed, sharing the same integrated case design. Jobs left Apple in 1985.
In 1987, the Macintosh II brought color graphics, but priced as a professional workstation and not a personal computer. Beginning in 1994 with the Power Macintosh, the Mac transitioned from Motorola 68000 series processors to PowerPC. Despite the significant performance increase, the Mac was not fully competitive with commodity IBM PC compatibles throughout the 1990s.
The 1996 acquisition of NeXT returned Steve Jobs to Apple, whose focused product oversight pushed the Mac mainstream with the 1998 iMac G3, the Mac OS X operating system (renamed to macOS in 2016), and the Mac transition to Intel processors from 2005 to 2006. High pixel density Retina displays debuted in the iPhone 4 in 2010 and the MacBook Pro in 2012. In the 2010s, the Mac was neglected under CEO Tim Cook, especially for professional users, but was reinvigorated with new high-end Macs and the transition to Apple silicon, which had originated in iOS devices.
== History ==
=== 1979–1996: "Macintosh" era ===
In the late 1970s, the Apple II became one of the most popular computers, especially in education. After IBM introduced the IBM PC in 1981, its sales surpassed the Apple II. In response, Apple introduced the Lisa in 1983. The Lisa's graphical user interface was partially inspired by strategically licensed demonstrations of the Xerox Star. Lisa surpassed the Star with intuitive direct manipulation, like the ability to drag and drop files, double-click to launch applications, and move or resize windows by clicking and dragging instead of going through a menu. However, hampered by its high price of $9,995 (equivalent to $33,000 in 2023) and lack of available software, the Lisa was commercially unsuccessful.
Parallel to the Lisa's development, a skunkworks team at Apple was working on the Macintosh project. Conceived in 1979 by Jef Raskin, Macintosh was envisioned as an affordable, easy-to-use computer for the masses. Raskin named the computer after his favorite type of apple, the McIntosh. The initial team consisted of Raskin, hardware engineer Burrell Smith, and Apple co-founder Steve Wozniak. In 1981, Steve Jobs was removed from the Lisa team and joined Macintosh, and was able to gradually take control of the project due to Wozniak's temporary absence after an airplane crash. Under Jobs, the Mac grew to resemble the Lisa, with a mouse and a more intuitive graphical interface, at a quarter of the Lisa's price.
Upon its January 1984 launch, the first Macintosh was described as "revolutionary" by The New York Times. Sales initially met projections, but dropped due to the machine's low performance, single floppy disk drive requiring frequent disk swapping, and initial lack of applications. Author Douglas Adams said: "But what I (and I think everybody else who bought the machine in the early days) fell in love with was not the machine itself, which was ridiculously slow and underpowered, but a romantic idea of the machine. And that romantic idea had to sustain me through the realities of actually working on the 128K Mac." Most of the original Macintosh team left Apple, and some followed Jobs to found NeXT after he was forced out by CEO John Sculley. The first Macintosh nevertheless generated enthusiasm among buyers and some developers, who rushed to develop entirely new programs for the platform, including PageMaker, MORE, and Excel. Apple soon released the Macintosh 512K with improved performance and an external floppy drive. The Macintosh is credited with popularizing the graphical user interface, Jobs's fascination with typography gave it an unprecedented variety of fonts and type styles like italics, bold, shadow, and outline. It is the first WYSIWYG computer, and due in large part to PageMaker and Apple's LaserWriter printer, it ignited the desktop publishing market, turning the Macintosh from an early let-down into a notable success. Levy called desktop publishing the Mac's "Trojan horse" in the enterprise market, as colleagues and executives tried these Macs and were seduced into requesting one for themselves. PageMaker creator Paul Brainerd said: "You would see the pattern. A large corporation would buy PageMaker and a couple of Macs to do the company newsletter. The next year you'd come back and there would be thirty Macintoshes. The year after that, three hundred."
In late 1985, Bill Atkinson, one of the few remaining employees to have been on the original Macintosh team, proposed that Apple create a Dynabook, Alan Kay's concept for a tablet computer that stores and organizes knowledge. Sculley rebuffed him, so he adapted the idea into a Mac program, HyperCard, whose cards store any information—text, image, audio, video—with the memex-like ability to semantically link cards together. HyperCard was released in 1987 and bundled with every Macintosh.
In the late 1980s, Jean-Louis Gassée, a Sculley protégé who had succeeded Jobs as head of the Macintosh division, made the Mac more expandable and powerful to appeal to tech enthusiasts and enterprise customers. This strategy led to the successful 1989 release of the Macintosh II, which appealed to power users and gave the lineup momentum. However, Gassée's "no-compromise" approach foiled Apple's first laptop, the Macintosh Portable, which has many uncommon power user features, but is almost as heavy as the original Macintosh at twice its price. Soon after its launch, Gassée was fired.
Since the Mac's debut, Sculley had opposed lowering the company's profit margins, and Macintoshes were priced far above entry-level MS-DOS compatible computers. Steven Levy said that though Macintoshes were superior, the cheapest Mac cost almost twice as much as the cheapest IBM PC compatible. Sculley also resisted licensing the Mac OS to competing hardware vendors, who could have undercut Apple on pricing and jeopardized its hardware sales, as IBM PC compatibles had done to IBM. These early strategic steps caused the Macintosh to lose its chance at becoming the dominant personal computer platform. Though senior management demanded high-margin products, a few employees disobeyed and set out to create a computer that would live up to the original Macintosh's slogan, "[a] computer for the rest of us", which the market clamored for. In a pattern typical of Apple's early era, of skunkworks projects like Macintosh and Macintosh II lacking adoption by upper management who were late to realize the projects' merit, this once-renegade project was actually endorsed by senior management following market pressures. In 1990 came the Macintosh LC and the more affordable Macintosh Classic, the first model under $1,000 (equivalent to $2,300 in 2023). Between 1984 and 1989, Apple had sold one million Macs, and another 10 million over the following five years.
In 1991, the Macintosh Portable was replaced with the smaller and lighter PowerBook 100, the first laptop with a palm rest and trackball in front of the keyboard. The PowerBook brought $1 billion of revenue within one year, and became a status symbol. By then, the Macintosh represented 10% to 15% of the personal computer market. Fearing a decline in market share, Sculley co-founded the AIM alliance with IBM and Motorola to create a new standardized computing platform, which led to the creation of the PowerPC processor architecture, and the Taligent operating system. In 1992, Apple introduced the Macintosh Performa line, which "grew like ivy" into a disorienting number of barely differentiated models in an attempt to gain market share. This backfired by confusing customers, but the same strategy soon afflicted the PowerBook line. Michael Spindler continued this approach when he succeeded Sculley as CEO in 1993. He oversaw the Mac's transition from Motorola 68000 series to PowerPC and the release of Apple's first PowerPC machine, the well-received Power Macintosh.
Many new Macintoshes suffered from inventory and quality control problems. The 1995 PowerBook 5300 was plagued with quality problems, with several recalls as some units even caught fire. Pessimistic about Apple's future, Spindler repeatedly attempted to sell Apple to other companies, including IBM, Kodak, AT&T, Sun, and Philips. In a last-ditch attempt to fend off Windows, Apple yielded and started a Macintosh clone program, which allowed other manufacturers to make System 7 computers. However, this only cannibalized the sales of Apple's higher-margin machines. Meanwhile, Windows 95 was an instant hit with customers. Apple was struggling financially as its attempts to produce a System 7 successor had all failed with Taligent, Star Trek, and Copland, and its hardware was stagnant. The Mac was no longer competitive, and its sales entered a tailspin. Corporations abandoned Macintosh in droves, replacing it with cheaper and more technically sophisticated Windows NT machines for which far more applications and peripherals existed. Even some Apple loyalists saw no future for the Macintosh. Once the world's second largest computer vendor after IBM, Apple's market share declined precipitously from 9.4% in 1993 to 3.1% in 1997. Bill Gates was ready to abandon Microsoft Office for Mac, which would have slashed any remaining business appeal the Mac had. Gil Amelio, Spindler's successor, failed to negotiate a deal with Gates.
In 1996, Spindler was succeeded by Amelio, who searched for an established operating system to acquire or license for the foundation of a new Macintosh operating system. He considered BeOS, Solaris, Windows NT, and NeXT's NeXTSTEP, eventually choosing the last. Apple acquired NeXT on December 20, 1996, returning its co-founder, Steve Jobs.
=== 1997–2011: Steve Jobs era ===
NeXT had developed the mature NeXTSTEP operating system with strong multimedia and Internet capabilities. NeXTSTEP was also popular among programmers, financial firms, and academia for its object-oriented programming tools for rapid application development. In an eagerly anticipated speech at the January 1997 Macworld trade show, Steve Jobs previewed Rhapsody, a merger of NeXTSTEP and Mac OS as the foundation of Apple's new operating system strategy. At the time, Jobs only served as advisor, and Amelio was released in July 1997. Jobs was formally appointed interim CEO in September, and permanent CEO in January 2000. To continue turning the company around, Jobs streamlined Apple's operations and began layoffs. He negotiated a deal with Bill Gates in which Microsoft committed to releasing new versions of Office for Mac for five years, investing $150 million in Apple, and settling an ongoing lawsuit in which Apple alleged that Windows had copied the Mac's interface. In exchange, Apple made Internet Explorer the default Mac browser. The deal was closed hours before Jobs announced it at the August 1997 Macworld.
Jobs returned focus to Apple. The Mac lineup had been incomprehensible, with dozens of hard-to-distinguish models. He streamlined it into four quadrants, a laptop and a desktop each for consumers and professionals. Apple also discontinued several Mac accessories, including the StyleWriter printer and the Newton PDA. These changes were meant to refocus Apple's engineering, marketing, and manufacturing efforts so that more care could be dedicated to each product. Jobs also stopped licensing Mac OS to clone manufacturers, which had cost Apple ten times more in lost sales than it received in licensing fees. Jobs made a deal with the largest computer reseller, CompUSA, to carry a "store within a store" that would better showcase Macs and their software and peripherals. According to Apple, the Mac's share of computer sales in those stores went from 3% to 14%. In November, the online Apple Store launched with built-to-order Mac configurations without a middleman. When Tim Cook was hired as chief operations officer in March 1998, he closed Apple's inefficient factories and outsourced Mac production to Taiwan. Within months, he rolled out a new ERP system and implemented just-in-time manufacturing principles. This practically eliminated Apple's costly unsold inventory, and within one year, Apple had the industry's most efficient inventory turnover.
Jobs's top priority was "to ship a great new product". The first is the iMac G3, an all-in-one computer that was meant to make the Internet intuitive and easy to access. While PCs came in functional beige boxes, Jony Ive gave the iMac a radical and futuristic design, meant to make the product less intimidating. Its oblong case is made of translucent plastic in Bondi blue, later revised with many colors. Ive added a handle on the back to make the computer more approachable. Jobs declared the iMac would be "legacy-free", succeeding ADB and SCSI with an infrared port and cutting-edge USB ports. Though USB had industry backing, it was still absent from most PCs and USB 1.1 was only standardized one month after the iMac's release. He also controversially removed the floppy disk drive and replaced it with a CD drive. The iMac was unveiled in May 1998, and released in August. It was an immediate commercial success and became the fastest-selling computer in Apple's history, with 800,000 units sold before the year ended. Vindicating Jobs on the Internet's appeal to consumers, 32% of iMac buyers had never used a computer before, and 12% were switching from PCs. The iMac reestablished the Mac's reputation as a trendsetter: for the next few years, translucent plastic became the dominant design trend in numerous consumer products.
Apple knew it had lost its chance to compete in the Windows-dominated enterprise market, so it prioritized design and ease of use to make the Mac more appealing to average consumers, and even teens. The "Apple New Product Process" was launched as a more collaborative product development process for the Mac, with concurrent engineering principles. From then, product development was no longer driven primarily by engineering and with design as an afterthought. Instead, Ive and Jobs first defined a new product's "soul", before it was jointly developed by the marketing, engineering, and operations teams. The engineering team was led by the product design group, and Ive's design studio was the dominant voice throughout the development process.
The next two Mac products in 1999, the Power Mac G3 (nicknamed "Blue and White") and the iBook, introduced industrial designs influenced by the iMac, incorporating colorful translucent plastic and carrying handles. The iBook introduced several innovations: a strengthened hinge instead of a mechanical latch to keep it closed, ports on the sides rather than on the back, and the first laptop with built-in Wi-Fi. It became the best selling laptop in the U.S. during the fourth quarter of 1999. The professional-oriented Titanium PowerBook G4 was released in 2001, becoming the lightest and thinnest laptop in its class, and the first laptop with a wide-screen display; it also debuted a magnetic latch that secures the lid elegantly.
The design language of consumer Macs shifted again from colored plastics to white polycarbonate with the introduction of the 2001 Dual USB "Ice" iBook. To increase the iBook's durability, it eliminated doors and handles, and gained a more minimalistic exterior. Ive attempted to go beyond the quadrant with Power Mac G4 Cube, an innovation beyond the computer tower in a professional desktop far smaller than the Power Mac. The Cube failed in the market and was withdrawn from sale after one year. However, Ive considered it beneficial, because it helped Apple gain experience in complex machining and miniaturization.
The development of a successor to the old Mac OS was well underway. Rhapsody had been previewed at WWDC 1997, featuring a Mach kernel and BSD foundations, a virtualization layer for old Mac OS apps (codenamed Blue Box), and an implementation of NeXTSTEP APIs called OpenStep (codenamed Yellow Box). Apple open-sourced the core of Rhapsody as the Darwin operating system. After several developer previews, Apple also introduced the Carbon API, which provided a way for developers to more easily make their apps native to Mac OS X without rewriting them in Yellow Box. Mac OS X was publicly unveiled in January 2000, introducing the modern Aqua graphical user interface, and a far more stable Unix foundation, with memory protection and preemptive multitasking. Blue Box became the Classic environment, and Yellow Box was renamed Cocoa. Following a public beta, the first version of Mac OS X, version 10.0 Cheetah, was released in March 2001.
In 1999, Apple launched its new "digital lifestyle" strategy of which the Mac became a "digital hub" and centerpiece with several new applications. In October 1999, the iMac DV gained FireWire ports, allowing users to connect camcorders and easily create movies with iMovie; the iMac gained a CD burner and iTunes, allowing users to rip CDs, make playlists, and burn them to blank discs. Other applications include iPhoto for organizing and editing photos, and GarageBand for creating and mixing music and other audio. The digital lifestyle strategy entered other markets, with the iTunes Store, iPod, iPhone, iPad, and the 2007 renaming from Apple Computer Inc. to Apple Inc. By January 2007, the iPod was half of Apple's revenues.
New Macs include the white "Sunflower" iMac G4. Ive designed a display to swivel with one finger, so that it "appear[ed] to defy gravity". In 2003, Apple released the aluminum 12-inch and 17-inch PowerBook G4, proclaiming the "Year of the Notebook". With the Microsoft deal expiring, Apple also replaced Internet Explorer with its new browser, Safari. The first Mac Mini was intended to be assembled in the U.S., but domestic manufacturers were slow and had insufficient quality processes, leading Apple to Taiwanese manufacturer Foxconn. The affordably priced Mac Mini desktop was introduced at Macworld 2005, alongside the introduction of the iWork office suite.
Serlet and Tevanian were both initiating the secret project asked by Steve Jobs to propose to Sony executives, in 2001, to sell MacOS on Vaio laptops. They shown them a demonstration at a golf party in Hawaii, with the most expensive Vaio laptop they could have acquired. But due to a bad timing, Sony refused, arguing their Vaio sales just started to grow after years of difficulties.
==== Intel transition and "back to the Mac" ====
With PowerPC chips falling behind in performance, price, and efficiency, Steve Jobs announced in 2005 the Mac transition to Intel processors, because the operating system had been developed for both architectures since the beginning. PowerPC apps run using transparent Rosetta emulation, and Windows boots natively using Boot Camp. This transition helped contribute to a few years of growth in Mac sales.
After the iPhone's 2007 release, Apple began a multi-year effort to bring many iPhone innovations "back to the Mac", including multi-touch gesture support, instant wake from sleep, and fast flash storage. At Macworld 2008, Jobs introduced the first MacBook Air by taking it out of a manila envelope, touting it as the "world's thinnest notebook". The MacBook Air favors wireless technologies over physical ports, and lacks FireWire, an optical drive, or a replaceable battery. The Remote Disc feature accesses discs in other networked computers. A decade after its launch, journalist Tom Warren wrote that the MacBook Air had "immediately changed the future of laptops", starting the ultrabook trend. OS X Lion added new software features first introduced with the iPad, such as FaceTime, full-screen apps, document autosaving and versioning, and a bundled Mac App Store to replace software install discs with online downloads. It gained support for Retina displays, which had been introduced earlier with the iPhone 4. iPhone-like multi-touch technology was progressively added to all MacBook trackpads, and to desktop Macs through the Magic Mouse, and Magic Trackpad. The 2010 MacBook Air added an iPad-inspired standby mode, "instant-on" wake from sleep, and flash memory storage.
After criticism by Greenpeace, Apple improved the ecological performance of its products. The 2008 MacBook Air is free of toxic chemicals like mercury, bromide, and PVC, and with smaller packaging. The enclosures of the iMac and unibody MacBook Pro were redesigned with the more recyclable aluminum and glass.
On February 24, 2011, the MacBook Pro became the first computer to support Intel's new Thunderbolt connector, with two-way transfer speeds of 10 Gbit/s, and backward compatibility with Mini DisplayPort.
=== 2012–present: Tim Cook era ===
Due to deteriorating health, Steve Jobs resigned as CEO on August 24, 2011, and Tim Cook was named as his successor. Cook's first keynote address launched iCloud, moving the digital hub from the Mac to the cloud. In 2012, the MacBook Pro was refreshed with a Retina display, and the iMac was slimmed and lost its SuperDrive.
During Cook's first few years as CEO, Apple fought media criticisms that it could no longer innovate without Jobs. In 2013, Apple introduced a new cylindrical Mac Pro, with marketing chief Phil Schiller exclaiming "Can't innovate anymore, my ass!". The new model had a miniaturized design with a glossy dark gray cylindrical body and internal components organized around a central cooling system. Tech reviewers praised the 2013 Mac Pro for its power and futuristic design; however, it was poorly received by professional users, who criticized its lack of upgradability and the removal of expansion slots.
The iMac was refreshed with a 5K Retina display in 2014, making it the highest-resolution all-in-one desktop computer. The MacBook was reintroduced in 2015, with a completely redesigned aluminum unibody chassis, a 12-inch Retina display, a fanless low-power Intel Core M processor, a much smaller logic board, a new Butterfly keyboard, a single USB-C port, and a solid-state Force Touch trackpad with pressure sensitivity. It was praised for its portability, but criticized for its lack of performance, the need to use adapters to use most USB peripherals, and a high starting price of $1,299 (equivalent to $1,700 in 2023). In 2015, Apple started a service program to address a widespread GPU defect in the 15-inch 2011 MacBook Pro, which could cause graphical artifacts or prevent the machine from functioning entirely.
==== Neglect of professional users ====
The Touch Bar MacBook Pro was released in October 2016. It was the thinnest MacBook Pro ever made, replaced all ports with four Thunderbolt 3 (USB-C) ports, gained a thinner "Butterfly" keyboard, and replaced function keys with the Touch Bar. The Touch Bar was criticized for making it harder to use the function keys by feel, as it offered no tactile feedback. Many users were also frustrated by the need to buy dongles, particularly professional users who relied on traditional USB-A devices, SD cards, and HDMI for video output. A few months after its release, users reported a problem with stuck keys and letters being skipped or repeated. iFixit attributed this to the ingress of dust or food crumbs under the keys, jamming them. Since the Butterfly keyboard was riveted into the laptop's case, it could only be serviced at an Apple Store or authorized service center. Apple settled a $50m class-action lawsuit over these keyboards in 2022. These same models were afflicted by "flexgate": when users closed and opened the machine, they would risk progressively damaging the cable responsible for the display backlight, which was too short. The $6 cable was soldered to the screen, requiring a $700 repair.
Senior Vice President of Industrial Design Jony Ive continued to guide product designs towards simplicity and minimalism. Critics argued that he had begun to prioritize form over function, and was excessively focused on product thinness. His role in the decisions to switch to fragile Butterfly keyboards, to make the Mac Pro non-expandable, and to remove USB-A, HDMI and the SD card slot from the MacBook Pro were criticized.
The long-standing keyboard issue on MacBook Pros, Apple's abandonment of the Aperture professional photography app, and the lack of Mac Pro upgrades led to declining sales and a widespread belief that Apple was no longer committed to professional users. After several years without any significant updates to the Mac Pro, Apple executives admitted in 2017 that the 2013 Mac Pro had not met expectations, and said that the company had designed themselves into a "thermal corner", preventing them from releasing a planned dual-GPU successor. Apple also unveiled their future product roadmap for professional products, including plans for an iMac Pro as a stopgap and an expandable Mac Pro to be released later. The iMac Pro was revealed at WWDC 2017, featuring updated Intel Xeon W processors and Radeon Pro Vega graphics.
In 2018, Apple released a redesigned MacBook Air with a Retina display, Butterfly keyboard, Force Touch trackpad, and Thunderbolt 3 USB-C ports. The Butterfly keyboard went through three revisions, incorporating silicone gaskets in the key mechanism to prevent keys from being jammed by dust or other particles. However, many users continued to experience reliability issues with these keyboards, leading Apple to launch a program to repair affected keyboards free of charge. Higher-end models of the 15-inch 2018 MacBook Pro faced another issue where the Core i9 processor reached unusually high temperatures, resulting in reduced CPU performance from thermal throttling. Apple issued a patch to address this issue via a macOS supplemental update, blaming a "missing digital key" in the thermal management firmware.
The 2019 16-inch MacBook Pro and 2020 MacBook Air replaced the unreliable Butterfly keyboard with a redesigned scissor-switch Magic Keyboard. On the MacBook Pros, the Touch Bar and Touch ID were made standard, and the Esc key was detached from the Touch Bar and returned to being a physical key. At WWDC 2019, Apple unveiled a new Mac Pro with a larger case design that allows for hardware expandability, and introduced a new expansion module system (MPX) for modules such as the Afterburner card for faster video encoding. Almost every part of the new Mac Pro is user-replaceable, with iFixit praising its high user-repairability. It received positive reviews, with reviewers praising its power, modularity, quiet cooling, and Apple's increased focus on professional workflows.
==== Apple silicon transition ====
In April 2018, Bloomberg reported Apple's plan to replace Intel chips with ARM processors similar to those in its phones, causing Intel's shares to drop by 9.2%. The Verge commented on the rumors, that such a decision made sense, as Intel was failing to make significant improvements to its processors, and could not compete with ARM chips on battery life.
At WWDC 2020, Tim Cook announced that the Mac would be transitioning to Apple silicon chips, built upon an ARM architecture, over a two-year timeline. The Rosetta 2 translation layer was also introduced, enabling Apple silicon Macs to run Intel apps. On November 10, 2020, Apple announced their first system-on-a-chip designed for the Mac, the Apple M1, and a series of Macs that would ship with the M1: the MacBook Air, Mac Mini, and the 13-inch MacBook Pro. These new Macs received highly positive reviews, with reviewers highlighting significant improvements in battery life, performance, and heat management compared to previous generations.
The iMac Pro was quietly discontinued on March 6, 2021. On April 20, 2021, a new 24-inch iMac was revealed, featuring the M1 chip, seven new colors, thinner white bezels, a higher-resolution 1080p webcam, and an enclosure made entirely from recycled aluminum.
On October 18, 2021, Apple announced new 14-inch and 16-inch MacBook Pros, featuring the more powerful M1 Pro and M1 Max chips, a bezel-less mini-LED 120 Hz ProMotion display, and the return of MagSafe and HDMI ports, and the SD card slot.
On March 8, 2022, the Mac Studio was unveiled, also featuring the M1 Max chip and the new M1 Ultra chip in a similar form factor to the Mac Mini. It drew highly positive reviews for its flexibility and wide range of available ports. Its performance was deemed "impressive", beating the highest-end Mac Pro with a 28-core Intel Xeon chip, while being significantly more power efficient and compact. It was introduced alongside the Studio Display, and was meant to replace the 27-inch iMac, which was discontinued on the same day.
==== Post-Apple silicon transition ====
At WWDC 2022, Apple announced an updated MacBook Air based on a new M2 chip. It incorporates several changes from the 14-inch MacBook Pro, such as a flat, slab-shaped design, full-sized function keys, MagSafe charging, and a Liquid Retina display, with rounded corners and a display cutout incorporating a 1080p webcam.
The Mac Studio with M2 Max and M2 Ultra chips and the Mac Pro with M2 Ultra chip was unveiled at WWDC 2023, and the Intel-based Mac Pro was discontinued on the same day, completing the Mac transition to Apple silicon chips. The Mac Studio was received positively as a modest upgrade over the previous generation, albeit similarly-priced PCs could be equipped with faster GPUs. However, the Apple silicon-based Mac Pro was criticized for several regressions, including memory capacity and a complete lack of CPU or GPU expansion options. A 15-inch MacBook Air was also introduced, and is the largest display included on a consumer-level Apple laptop.
The MacBook Pro was updated on October 30, 2023 with updated M3 Pro and M3 Max chips using a 3 nm process node, as well as the standard M3 chip in a refreshed iMac and a new base model MacBook Pro. Reviewers lamented the base memory configuration of 8 GB on the standard M3 MacBook Pro. In March 2024, the MacBook Air was also updated to include the M3 chip.
== Product lineup ==
== Marketing ==
The original Macintosh was marketed at Super Bowl XVIII with the highly acclaimed "1984" ad, directed by Ridley Scott. The ad alluded to George Orwell's novel Nineteen Eighty-Four, and symbolized Apple's desire to "rescue" humanity from the conformity of computer industry giant IBM. The ad is now considered a "watershed event" and a "masterpiece." Before the Macintosh, high-tech marketing catered to industry insiders rather than consumers, so journalists covered technology like the "steel or automobiles" industries, with articles written for a highly technical audience. The Macintosh launch event pioneered event marketing techniques that have since become "widely emulated" in Silicon Valley, by creating a mystique about the product and giving an inside look into its creation. Apple took a new "multiple exclusives" approach regarding the press, giving "over one hundred interviews to journalists that lasted over six hours apiece", and introduced a new "Test Drive a Macintosh" campaign.
Apple's brand, which established a "heartfelt connection with consumers", is cited as one of the keys to the Mac's success. After Steve Jobs's return to the company, he launched the Think different ad campaign, positioning the Mac as the best computer for "creative people who believe that one person can change the world". The campaign featured black-and-white photographs of luminaries like Albert Einstein, Gandhi, and Martin Luther King Jr., with Jobs saying: "if they ever used a computer, it would have been a Mac". The ad campaign was critically acclaimed and won several awards, including a Primetime Emmy. In the 2000s, Apple continued to use successful marketing campaigns to promote the Mac line, including the Switch and Get a Mac campaigns.
Apple's focus on design and build quality has helped establish the Mac as a high-end, premium brand. The company's emphasis on creating iconic and visually appealing designs for its computers has given them a "human face" and made them stand out in a crowded market. Apple has long made product placements in high-profile movies and television shows to showcase Mac computers, like Mission: Impossible, Legally Blonde, and Sex and the City. Apple is known for not allowing producers to show villains using Apple products. Its own shows produced for the Apple TV+ streaming service feature prominent use of MacBooks.
The Mac is known for its highly loyal customer base. In 2022, the American Customer Satisfaction Index gave the Mac the highest customer satisfaction score of any personal computer, at 82 out of 100. In that year, Apple was the fourth largest vendor of personal computers, with a market share of 8.9%.
== Hardware ==
Apple outsources the production of its hardware to Asian manufacturers like Foxconn and Pegatron. As a highly vertically integrated company developing its own operating system and chips, it has tight control over all aspects of its products and deep integration between hardware and software.
All Macs in production use ARM-based Apple silicon processors and have been praised for their performance and power efficiency. They can run Intel apps through the Rosetta 2 translation layer, and iOS and iPadOS apps distributed via the App Store. These Mac models come equipped with high-speed Thunderbolt 4 or USB 4 connectivity, with speeds up to 40 Gbit/s. Apple silicon Macs have custom integrated graphics rather than graphics cards. MacBooks are recharged with either USB-C or MagSafe connectors, depending on the model.
Apple sells accessories for the Mac, including the Studio Display and Pro Display XDR external monitors, the AirPods line of wireless headphones, and keyboards and mice such as the Magic Keyboard, Magic Trackpad, and Magic Mouse.
== Software ==
Macs run the macOS operating system, which is the second most widely used desktop OS according to StatCounter. Macs can also run Windows, Linux, or other operating systems through virtualization, emulation, or multi-booting.
macOS is the successor of the classic Mac OS, which had nine releases between 1984 and 1999. The last version of classic Mac OS, Mac OS 9, was introduced in 1999. Mac OS 9 was succeeded by Mac OS X in 2001. Over the years, Mac OS X was rebranded first to OS X and later to macOS.
macOS is a derivative of NextSTEP and FreeBSD. It uses the XNU kernel, and the core of macOS has been open-sourced as the Darwin operating system. macOS features the Aqua user interface, the Cocoa set of frameworks, and the Objective-C and Swift programming languages. Macs are deeply integrated with other Apple devices, including the iPhone and iPad, through Continuity features like Handoff, Sidecar, Universal Control, and Universal Clipboard.
The first version of Mac OS X, version 10.0, was released in March 2001. Subsequent releases introduced major changes and features to the operating system. 10.4 Tiger added Spotlight search; 10.6 Snow Leopard brought refinements, stability, and full 64-bit support; 10.7 Lion introduced many iPad-inspired features; 10.10 Yosemite introduced a complete user interface revamp, replacing skeuomorphic designs with iOS 7-esque flat designs; 10.12 Sierra added the Siri voice assistant and Apple File System (APFS) support; 10.14 Mojave added a dark user interface mode; 10.15 Catalina dropped support for 32-bit apps; 11 Big Sur introduced an iOS-inspired redesign of the user interface, 12 Monterey added the Shortcuts app, Low Power Mode, and AirPlay to Mac; and 13 Ventura added Stage Manager, Continuity Camera, and passkeys.
The Mac has a variety of apps available, including cross-platform apps like Google Chrome, Microsoft Office, Adobe Creative Cloud, Mathematica, Visual Studio Code, Ableton Live, and Cinema 4D. Apple has also developed several apps for the Mac, including Final Cut Pro, Logic Pro, iWork, GarageBand, and iMovie. A large amount of open-source software applications run natively on macOS, such as LibreOffice, VLC, and GIMP, and command-line programs, which can be installed through Macports and Homebrew. Many applications for Linux or BSD also run on macOS, often using X11. Apple's official integrated development environment (IDE) is Xcode, allowing developers to create apps for the Mac and other Apple platforms.
The latest release of macOS is macOS 14 Sonoma, released on September 26, 2023.
== Timeline ==
Source: Glen Sanford, Apple History, apple-history.com
== References ==
=== Bibliography ===
Hertzfeld, Andy (2004). Revolution in the Valley: The Insanely Great Story of How the Mac was made. O'Reilly. ISBN 0-596-00719-1.
Isaacson, Walter (2011). Steve Jobs (1st ed.). New York, NY: Simon & Schuster. ISBN 978-1-4516-4853-9.
Levy, Steven (June 2000). Insanely Great: The Life and Times of Macintosh, the Computer that Changed Everything. Penguin Publishing Group. ISBN 978-0-14-029177-3.
Linzmayer, Owen W. (2004). Apple Confidential 2.0: The Definitive History of the World's Most Colorful Company. No Starch Press. ISBN 978-1-59327-010-0.
Malone, Michael Shawn (1999). Infinite Loop: How the World's Most Insanely Great Computer Company Went Insane. Currency/Doubleday. ISBN 978-0-385-48684-2.
Mickle, Tripp (May 3, 2022). After Steve: How Apple Became a Trillion-Dollar Company and Lost Its Soul. HarperCollins Publishers. ISBN 978-0-06-300981-3.
Schlender, Brent; Tetzeli, Rick (2015). Becoming Steve Jobs: The Evolution of a Reckless Upstart into a Visionary Leader. Crown Business. ISBN 978-0-7710-7914-6.
Singh, Amit (June 19, 2006). Mac OS X Internals: A Systems Approach. Addison-Wesley Professional. ISBN 978-0-13-270226-3.
Sandberg-Diment, Erik (January 24, 1984). "Hardware review: Apple Weighs In With Its Macintosh". The New York Times. ISSN 0362-4331.
== Further reading ==
== External links ==
Official website | Mac, short for Macintosh (its official name until 1999), is a family of personal computers designed and marketed by Apple. The name Macintosh is a reference to a type of apple called McIntosh. The product lineup includes the MacBook Air and MacBook Pro laptops, and the iMac, Mac Mini, Mac Studio, and Mac Pro desktops. Macs are sold with the macOS operating system.
Jef Raskin conceived the Macintosh project in 1979, which was usurped and redefined by Apple co-founder Steve Jobs in 1981. The Macintosh was launched in January 1984, after Apple's "1984" advertisement during Super Bowl XVIII. The system has a 9-inch monochrome monitor and 3 1/2-inch floppy drive built into the case and shipped with a one-button mouse. A series of incrementally improved models followed, sharing the same integrated case design. Jobs left Apple in 1985.
In 1987, the Macintosh II brought color graphics, but priced as a professional workstation and not a personal computer. Beginning in 1994 with the Power Macintosh, the Mac transitioned from Motorola 68000 series processors to PowerPC. Despite the significant performance increase, the Mac was not fully competitive with commodity IBM PC compatibles throughout the 1990s.
The 1996 acquisition of NeXT returned Steve Jobs to Apple, whose focused product oversight pushed the Mac mainstream with the 1998 iMac G3, the Mac OS X operating system (renamed to macOS in 2016), and the Mac transition to Intel processors from 2005 to 2006. High pixel density Retina displays debuted in the iPhone 4 in 2010 and the MacBook Pro in 2012. In the 2010s, the Mac was neglected under CEO Tim Cook, especially for professional users, but was reinvigorated with new high-end Macs and the transition to Apple silicon, which had originated in iOS devices.
| 14 |
348 | mac | Mac (film) (wikipedia) | Mac is a 1992 American drama film co-written and directed by John Turturro, in his directorial debut. It stars Turturro alongside Michael Badalucco, Katherine Borowitz, Carl Capotorto, Nicholas Turturro and Ellen Barkin. It won the Caméra d'Or award at the 1992 Cannes Film Festival and was nominated for an Independent Spirit Award.
== Synopsis ==
Niccolo (Mac) Vitelli is the oldest of three brothers and becomes the de facto head of their family after their father dies. Their father was in construction and the brothers follow in his footsteps. At first, they work for Polowski, who cuts corners and does not do an adequate job, as well as being verbally abusive to his employees with no pride in his work. This causes them to start their own company - Vitelli Brothers Construction, which will be the opposite of Polowski. Mac starts becoming a tyrannical workaholic with obsessive concern about the quality of their work with worrying attention to detail. His intensity and driven ambition pushes his brothers away and breaks the family apart.
== Main cast ==
John Turturro as Niccolo "Mac" Vitelli
James Madio as Young Niccolo "Mac" Vitelli
Michael Badalucco as Vico Vitelli
Katherine Borowitz as Alice Stunder
Carl Capotorto as Bruno Vitelli
Nicholas Turturro as Tony Gloves
Matthew Sussman as Clarence
Ellen Barkin as Oona Goldfarb
Dennis Farina as Mr. Stunder
Olek Krupa as Polowski
Steven Randazzo as Gus
Mike Starr as Firefighter
Joe Paparone as Papa
Aida Turturro as Wife
Mario Todisco as Joe "The Mule"
Harry Bugin as Patient
Michael Imperioli
== References ==
== External links ==
Mac at IMDb
Mac at AllMovie | Mac is a 1992 American drama film co-written and directed by John Turturro, in his directorial debut. It stars Turturro alongside Michael Badalucco, Katherine Borowitz, Carl Capotorto, Nicholas Turturro and Ellen Barkin. It won the Caméra d'Or award at the 1992 Cannes Film Festival and was nominated for an Independent Spirit Award. | 2 |
349 | mac | Mac (nickname) (wikipedia) | As a nickname, Mac may refer to:
== In arts and media ==
Mac Brandt (born 1980), American actor
Mac Curtis (1939–2013), American musician
Mac DeMarco (born 1990), Canadian singer-songwriter, musician and producer
Mac Martin (1925-2022), American bluegrass musician
Mac McNeilly (born 1960), American drummer
Mac Miller (1992–2018), American rapper and record producer
Malcolm John "Mac" Rebennack (1940–2019), better known by the stage name Dr. John, American singer-songwriter, pianist and guitarist
Mac Sebree (1932–2010), American journalist, writer and publisher
McLean Stevenson (1927–1996), American actor
Mac Wiseman (1925–2019), American bluegrass singer
Akshay Kumar (born 1967), Indian film actor, known as "Mac" after the character portrayed by him in the 2005 comedy film Garam Masala
== In sport ==
Mac Cody (born 1972), American National Football League player
Mac Colville (1916–2003), Canadian National Hockey League player
Mac Evans (1884–1977), Australian cricket and soccer player
Mac Foster (1942–2010), American heavyweight boxer
Mac Jones (born 1998), American football player
Mac May (born 1999), American volleyball player
Mac McCain (born 1998), American football player
Clark McConachy (1895–1980), New Zealand billiards and snooker player
Stan McCormick (1923–1999), English rugby league footballer and coach
Macdonald Smith (1892–1949), Scottish golfer
Mac Suzuki (born 1975), Major League Baseball pitcher from Japan
== In other fields ==
Malcolm Baldrige Jr. (1922–1987), American businessman and United States Secretary of Commerce
McGeorge Bundy (1919–1996), United States National Security Advisor to Presidents John F. Kennedy and Lyndon B. Johnson
Charles H. MacDonald (1914–2002), American World War II fighter ace
Linious "Mac" McGee (1897–1988), Alaskan aviation pioneer and founder of McGee Airways
== See also ==
All pages with titles beginning with Mac
All pages with titles containing Mac
Mac (disambiguation)
Big Mac (disambiguation)
Johnny Mac (disambiguation)
Little Mac (disambiguation)
Mack (given name)
Ian McCulloch (singer) (born 1959), lead singer of the English band Echo & The Bunnymen, nicknamed "Mac the Mouth" | As a nickname, Mac may refer to: | 0 |
350 | mac | Mac (novel) (wikipedia) | Mac is a youth novel by John MacLean about a young teenage boy dealing with a sexual assault. Mac was published in 1987 by Houghton Mifflin.
Mac is a quiet 14-year-old schoolboy who is just discovering girls. A new girl, Jenny, joins his year group and all the 'state-of-the-art' kids boast how they are going to make her their girl. Mac is awkward and shy around her, but she makes the moves and picks him as he is different from all the other boys. But something happens to ruin their relationship.
Mac is sexually assaulted by the school doctor during a routine examination. As a consequence, Mac undergoes dramatic personality changes that leaves his friends and family baffled; he is hostile to all of their efforts to discover his problem.
A professional counselor at school finally earns his trust, and Mac reveals what happened during the physical examination.
== External links ==
A review in the New York Times | Mac is a youth novel by John MacLean about a young teenage boy dealing with a sexual assault. Mac was published in 1987 by Houghton Mifflin.
Mac is a quiet 14-year-old schoolboy who is just discovering girls. A new girl, Jenny, joins his year group and all the 'state-of-the-art' kids boast how they are going to make her their girl. Mac is awkward and shy around her, but she makes the moves and picks him as he is different from all the other boys. But something happens to ruin their relationship.
Mac is sexually assaulted by the school doctor during a routine examination. As a consequence, Mac undergoes dramatic personality changes that leaves his friends and family baffled; he is hostile to all of their efforts to discover his problem.
A professional counselor at school finally earns his trust, and Mac reveals what happened during the physical examination. | 8 |
351 | mac | Mac (rapper) (wikipedia) | McKinley Phipps, Jr. (born July 30, 1977), better known simply as Mac, is an American rapper from New Orleans' 3rd Ward. He began rapping as a child, releasing his debut album The Lyrical Midget at the age of 13 in 1990, under the stage name Lil Mac. Mac would eventually sign with Master P's No Limit Records and would grow to be one of the most critically acclaimed artists on the label, both as a solo rapper and as a member of the super group 504 Boyz. Mac released two solo albums and one album as part of the 504 Boyz on No Limit, including 1998's Shell Shocked, which peaked at #11 on the US Billboard 200.
In 2001, Mac was convicted of manslaughter and sentenced to 30 years in prison at the Elayn Hunt Correctional Center in Louisiana, and was released on parole on June 22, 2021 after serving 20 years of his sentence. Phipps maintained his innocence throughout, and his parents have campaigned to re-open the investigation into his case.
== Career ==
Mac was born McKinley Phipps, Jr. to Sheila Phipps and McKinley Phipps, Sr. in New Orleans, Louisiana, the oldest of their six children. He began his music career in 1990, and by the time he was 13 years old, under the name "Lil Mac", he released his debut album, The Lyrical Midget. The album was one of the earliest commercial hip-hop albums to come out of New Orleans, and featured production from New Orleans producer Mannie Fresh.
=== Late 1990s: No Limit Records, Shell Shocked, and World War III ===
Lil Mac joined the Psychoward, a New Orleans-based group consisting of 28 rappers, and the group released their debut album, www.psychoward.com, in 1997. After rejecting an offer to move to New York and sign with Def Jam Records, Lil Mac changed his name to simply Mac and signed with Master P's No Limit Records. He toured with No Limit throughout the U.S. and Europe, and made guest appearances on many other artists' albums before releasing his own. He was featured on Master P's Ghetto D, Mystikal's Unpredictable, and Mia X's Unlady Like, among others. The next year in 1998, Mac released his second solo album and first with No Limit, Shell Shocked. The album is Mac's most commercially successful to date, reaching #11 on the Billboard 200. Mac again was featured on many other No Limit artist's releases that year. In 1999, he released his second album on the label, World War III. While it was still on the label, this release differed from usual No Limit releases in that it was not exclusively produced by the production team Beats by the Pound, and featured only three guest appearances from major No Limit names Master P, C-Murder, and Silkk the Shocker. The album did not fare as well commercially as his first No Limit release, peaking at #44 on the Billboard 200. Mac's musical style differed from many other Southern hip hop artists in this period, and he often displayed a level of lyrical complexity that has come to be associated with East Coast hip hop.
=== 504 Boyz and later releases ===
World War III would be Mac's last album released on No Limit and his last solo album to date. In 2000, he joined the group 504 Boyz, whose name was a reference to the area code 504. The group was a collective of other No Limit rappers such as Master P, Silkk the Shocker, and C-Murder. Mac was with the group for one album, 2000's Goodfellas, which went gold and reached #2 on the Billboard 200. He was featured prominently on the group's hit single "Wobble Wobble", rapping the first verse and the chorus. The song reached #17 on the Billboard Hot 100 Phipps would be sentenced to a 30-year prison term for manslaughter after 19-year-old Barron C. Victor, Jr. died from a gunshot wound in a Louisiana nightclub in 2001.
In 2007, while Mac was still serving his prison term, No Limit released the album The Lost Tapes, which consisted of unreleased material Mac recorded with the label.
On May 31, 2012, DJ 5150 released the mixtape Uptown Veterans, a compilation of Mac's greatest hits.
Mac Phipps has announced his first album in 23 years, Son of the City, which comes just over a year after being released from prison after two decades behind bars. Son of the City was released on October 31, 2022, with features from Fiend, D1, Curren$y,3d Na'tee, Cognac, Rayvon Neal, and many more.
== Legal issues ==
On February 21, 2000, Phipps was scheduled to perform at Slidell, Louisiana nightclub Club Mercedes, but a fight broke out before the show that resulted in a gunshot that struck and killed 19-year-old Barron C Victor, Jr. after Victor attempted to break up the fight. Phipps was arrested and charged with second-degree murder of Victor. He was convicted of manslaughter and sentenced to thirty years in prison on September 21, 2001. He would serve his sentence at the Elayn Hunt Correctional Center in Louisiana. Days into the police investigation, Thomas Williams, a man who was working security that night at the club, confessed to shooting Victor after another patron charged him with a beer bottle. Despite this, police pursued charges against Phipps.
In December 2014, Northwestern University's Medill Justice Project (MJP), in partnership with The Lens, published the results of a three-month investigation of Phipps' conviction, revealing that a key eyewitness at his trial gave his private investigator an affidavit in 2013 that stated she was coerced into identifying Phipps as the shooter because of investigators' threats to charge her. Following Medill's investigation, David Lohr of The Huffington Post published the results of a four-month review of Phipps' conviction, further revealing that four other witnesses to the shooting told the publication that they also were threatened, intimidated or outright ignored by investigators. Phipps' family has since obtained affidavits from many of the individuals in an effort to get him a new trial.
On March 25, 2015, rapper Killer Mike told students at Dillard University in New Orleans that it was unacceptable for authorities to use rap lyrics in the prosecution of Phipps: "If we let this stand, what you're going to see is that tool is going to be used to wipe out an entire potential generation of [artists] out of our community."
Phipps has applied for the Louisiana governor’s clemency in 2016, asking to be released from prison for time served. In the petition sent to the Louisiana Board of Pardons and Parole he seeks a commutation due to a "wrongful conviction and excessive sentence", as "evidence developed over the last two years" which includes, among other things, findings from MJP's investigation.
On February 22, 2021, the Louisiana Board of Pardons and Parole voted for Phipps' immediate eligibility for parole. On April 8, 2021, the Louisiana governor granted Phipps clemency. According to Louisiana law, Phipps has one more hearing before he is released.
On June 22, 2021, Phipps was released from prison after serving twenty years.
== Discography ==
=== Studio albums ===
=== Collaboration albums ===
Goodfellas with 504 Boyz (2000)
=== Compilation albums ===
Lost Tapes (2007)
=== Mixtapes ===
Uptown Veterans (2012)
=== Singles ===
== References ==
== External links ==
Mac on Myspace
Mac at AllMusic | McKinley Phipps, Jr. (born July 30, 1977), better known simply as Mac, is an American rapper from New Orleans' 3rd Ward. He began rapping as a child, releasing his debut album The Lyrical Midget at the age of 13 in 1990, under the stage name Lil Mac. Mac would eventually sign with Master P's No Limit Records and would grow to be one of the most critically acclaimed artists on the label, both as a solo rapper and as a member of the super group 504 Boyz. Mac released two solo albums and one album as part of the 504 Boyz on No Limit, including 1998's Shell Shocked, which peaked at #11 on the US Billboard 200.
In 2001, Mac was convicted of manslaughter and sentenced to 30 years in prison at the Elayn Hunt Correctional Center in Louisiana, and was released on parole on June 22, 2021 after serving 20 years of his sentence. Phipps maintained his innocence throughout, and his parents have campaigned to re-open the investigation into his case.
| 5 |
352 | mac | 7+3 (chemotherapy) (wikipedia) | "7+3" in the context of chemotherapy is an acronym for a chemotherapy regimen that is most often used today (as of 2014) as first-line induction therapy (to induce remission) in acute myelogenous leukemia, excluding the acute promyelocytic leukemia form, which is better treated with ATRA and/or arsenic trioxide and requires less chemotherapy (if requires it at all, which is not always the case).
The name "7+3" comes from the duration of chemotherapy course, which consists of 7 days of standard-dose cytarabine, and 3 days of an anthracycline antibiotic or an anthracenedione, most often daunorubicin (can be substituted for doxorubicin or idarubicin or mitoxantrone).
== Dosing regimen ==
=== Standard-dose cytarabine plus daunorubicin (DA or DAC chemotherapy) ===
=== Standard-dose cytarabine plus idarubicin (IA or IAC chemotherapy) ===
=== Standard-dose cytarabine plus mitoxantrone (MA or MAC chemotherapy) ===
=== Intensified versions ===
There were attempts to intensify the "7+3" regimen in order to try to improve its efficacy. Attempts were made to prolong the course (cytarabine for 10 days instead of 7, or daunorubicin/idarubicin for 4–5 days instead of 3).
On the other hand, there were attempts to minimize the toxicity of the regimen by reducing the dose or the duration of the course. But this proved to compromise the efficacy of the regimen.
The addition of vinca alkaloids (vincristine or vinblastine) to the "7+3" regimen, which addition was quite popular in AML(ALL?) in old times (when the biology of AML and the differences between AML and ALL was poorly understood) proved to be harmful in AML, lowering the chance of the patient to get remission. This is because vinca alkaloids are rapidly deactivated in myeloid cells by their enzyme myeloperoxidase. So the vinca alkaloids do much more damage to the lymphoid cell lines (including the T-cell lines responsible for antileukemic immunity) than to the myeloid cell lines. Moreover, vinca alkaloids in the context of AML cause AML cells to undergo a cell cycle arrest in the phase that renders those cells less sensitive to cytarabine and anthracyclines.
Addition of glucocorticoids (like prednisolone) or methotrexate or alkylating drugs (like cyclophosphamide or melphalan) to the "7+3" regimen is also of no benefit in AML.
The addition of etoposide to the standard "7+3" regimen is sometimes of benefit in poor-risk patients (many of which are primary refractory to standard "7+3" induction regimens). It gave rise to the so-called ADE (or DAE = DA + etoposide) induction regimen in AML. The ADE induction (unlike, say, combinations of 7+3 with vinca alkaloids or prednisolone) is still sometimes used, especially in poor-risk AML patients.
The addition of 6-thioguanine gave rise to the DAT regimen, and the addition of 6-mercaptopurine gave rise to the DAM regimen.
== References == | "7+3" in the context of chemotherapy is an acronym for a chemotherapy regimen that is most often used today (as of 2014) as first-line induction therapy (to induce remission) in acute myelogenous leukemia, excluding the acute promyelocytic leukemia form, which is better treated with ATRA and/or arsenic trioxide and requires less chemotherapy (if requires it at all, which is not always the case).
The name "7+3" comes from the duration of chemotherapy course, which consists of 7 days of standard-dose cytarabine, and 3 days of an anthracycline antibiotic or an anthracenedione, most often daunorubicin (can be substituted for doxorubicin or idarubicin or mitoxantrone). | 1 |
353 | mac | Celtic onomastics (wikipedia) | Onomastics is an important source of information on the early Celts, as Greco-Roman historiography recorded Celtic names before substantial written information becomes available in any Celtic language.
Like Germanic names, early Celtic names are often dithematic.
== Suffixes ==
suffix -rix "ruler"
Ambiorix
Boiorix
Cingetorix
Dumnorix
Orgetorix
Vercingetorix
suffix -maris / -marus "great"
Britomaris
Indutiomarus
Viridomarus
== Celtic polytheism ==
Some information on prehistoric Celtic polytheism can be drawn from names in Irish and Welsh mythology, which often continue older theonyms:
Gwenhwyfar, from *Uindā Seibrā "White Phantom"
Brigid, from *Brigantia "the High one"
Lugh and Lleu, cognate with Gaulish Lugus
== Surnames ==
Many surnames of Gaelic origin in Ireland and the other Celtic nations derive from ancestors' names, nicknames, or descriptive names. In the first group can be placed surnames such as MacMurrough and MacCarthy, derived from patronymics, or O'Brien and O'Grady, derived from ancestral names.
Gaelic surnames derived from nicknames include Ó Dubhda (from Aedh ua Dubhda—Aedh, "the dark one"), O'Doherty (from Ó Dochartaigh, "destroyer" or "obtrusive"), Garvery (garbh, "rough" or "nasty"), Manton (mantach, "toothless"), Bane (bán, "white", as in "white hair"), Finn (fionn, "fair", as in "fair hair") and Kennedy (ceann éidigh, "ugly head")
Very few Gaelic surnames are derived from placenames or from venerated people or objects. Among those that are included in this small group, several can be shown to be derivations of Gaelic personal names or surnames. One notable exception is Ó Cuilleáin or O'Collins (from cuileann, "holly") as in the holly tree, considered one of the most sacred objects of pre-Christian Celtic culture. Another is Walsh (Irish: Breatnach), meaning Welsh.
In areas where certain family names are extremely common, extra names are added that sometimes follow this archaic pattern. In Ireland, for example, where Murphy is an exceedingly common name, particular Murphy families or extended families are nicknamed, so that Denis Murphy's family were called 'The Weavers" and Denis himself was called "Denis 'The Weaver' Murphy". (See also O'Hay.)
For much the same reason, nicknames (e.g. "the Fada Burkes", "the long/tall Burkes"), father's names (e.g. "John Morrissey Ned") or mother's maiden name ("Kennedy" becoming "Kennedy-Lydon") can become colloquial or legal surnames. The Irish family of de Courcy descends from Anglo-Normans who came to Ireland following the Norman Conquest; the name is of French derivation, and indicates that the family once held a manor of that name in Normandy. The de Courcy family was prominent in County Cork from the earliest days of the Norman occupation and subsequently became prominent in Ireland.
In addition to all this, Irish-speaking areas still follow the old tradition of naming themselves after their father, grandfather, great-grandfather and so on. Examples include Mike Bartly Pat Reilly ("Mike, son of Bartholomew, son of Pat Reilly"), Seán Mícheál Seán Óg Pádraic Breathnach ("John, son of Michael, son of young John, son of Pat Breathnach"), Tom Paddy-Joe Seoige ("Tom, son of Paddy-Joe Seoige"), and Mary Bartly Mike Walsh ("Mary, daughter of Bartly, son of Mike Walsh"). Sometimes, the female line of the family is used, depending on how well the parent is known in the area the person resides in, e.g. Paddy Mary John ("Paddy, son of Mary, daughter of John"). A similar tradition continues even in English-speaking areas, especially in rural districts.
=== Surname prefixes ===
Bean: "Wife", pronounced [bʲanˠ].
De: "of the": a Norman-French habitational prefix used by some of the most common Irish surnames among which are De Búrca, Le Brún, De Barra, De Cíosóg, Devane and de Faoite. 'De' historically has signaled ownership of lands and was traditionally therefore a mark of prestige.
Mac (in English also written Mc, Mc, M’, and Mic): for most purposes, taken to mean 'son of', as in Mac Néill, 'son of Neil'. However, literally, the 'of' part does not come from the Mac prefix but from the patronymic that follows it; e.g., in the case of Mac Néill, Mac merely means 'son'; Néill (meaning 'of Neil') is the genitive form of Niall ('Neil'). In some cases, if the second word (nominal element) begins with a vowel, Mac then becomes Mag, as in Mag Eocháin.
Mhic: [vʲɪc]. Compressed form of bean mhic ("wife of the son of") e.g. Máire Mhic Néill (Máire, the wife of Mac Néill). This is the grammatically correct form of the prefix Mac always taken by a woman after marriage (e.g. a woman marrying someone of the surname Mac Néill would become Mhic Néill). Mhig (also pronounced [vʲɪc]) is used similarly to Mag in some cases (e.g. Mag Shamhráin/Mhig Shamhráin).
Maol: In Pagan times this was expressed as Mug, as in the case of Mug Nuadat. The literal expression of this is "slave of Nuada", i.e. "devotee of Nuada". In the Christian era the word Mael was used in its place for given names such as Mael Bridget, Mael Padraig, Mael Lagan, Mael Sechlainn, and Mael Martain. In later times, some of these given names evolved into surnames, e.g. Ó Máel Sechlainn and Mac Mael Martain or Mael Lagan, which became after the 15th century the name Milligan.
Fitz: a Norman-French word derived from the Latin word filius ("son"). It was used in patronymics by thousands of men in the early Norman period in Ireland (e.g. fitz Stephen, fitz Richard, fitz Robert, fitz William) and only on some occasions did it become used as an actual surname, the most famous example being the FitzGerald Earls of Kildare. Yet well into the 17th and 18th century it was used in certain areas dominated by the Hiberno-Normans of Ireland in its original form, as a patronymic. The Tribes of Galway were especially good at conserving this form, with examples such as John fitz John Bodkin and Michael Lynch fitz Arthur, used even as late as the early 19th century. A number of illegitimate descendants of the British royal family were given surnames with this element: some of the illegitimate children of King Charles II were named FitzCharles or FitzRoy ("son of the King"); those of King James II were named FitzJames; those of Prince William, Duke of Clarence and St Andrews (later King William IV) were named FitzClarence. Note that "Fitzpatrick" is not Norman: it is actually a Normanisation of the Gaelic surname Mac Ghiolla Phádraig.
Ó: In Old Irish as ua ("grandson", "descendant"). E.g., the ancestor of the O'Brien clan, Brian Boru (937–1014) was known in his lifetime as Brian mac Cennéide mac Lorcán ('Brian, the son of Cennéide, the son of Lorcán'). Not until the time of his grandsons and great-grandsons was the name O'Brien used as a surname, used to denote descent from an illustrious ancestor. It has for some three hundred years been written as O', but in recent years the apostrophe is often dropped, bringing it into line with early medieval forms. The apostrophe came into existence as an error by the English, when in the process of anglicizing the surnames in Ireland, the accent above the O was mistakenly recognized as an apostrophe; it is sometimes popularly thought to be an abbreviation of 'Of'.
Uí: This is the plural of Ó and is used in reference to a kin-group or clan, e.g. Uí Néill, in reference to the O'Neill clan. It is pronounced [i].
Ní: This is used for women instead of Ó before a surname (e.g. Máire Ní Bhriain, "Mary O'Brien"), and comes from a shortened form of the Irish word for a daughter.
Nic: This is used for women instead of Mac, but only if this is their maiden name, never their married name. Compressed form of iníon mhic ("daughter of the son of/Mac..."), e.g. Máire Nic Charthaigh ("Mary, daughter of McCarthy"). Nig [nʲɪc] is used in cases where the surname uses Mag e.g. Nig Shamhráin.
== See also ==
Celtic toponymy
Irish name
Place names in Ireland
Germanic name
Scottish Gaelic name
Scottish toponymy
Welsh surnames
Welsh toponymy
== References ==
== External links ==
Ancient Celtic names (behindthename.com)
Name Constructions in Gaulish | Onomastics is an important source of information on the early Celts, as Greco-Roman historiography recorded Celtic names before substantial written information becomes available in any Celtic language.
Like Germanic names, early Celtic names are often dithematic. | 1 |
354 | mac | Green Wing (wikipedia) | Green Wing is a British sitcom set in the fictional East Hampton Hospital. It was created by the same team behind the sketch show Smack the Pony – Channel 4 commissioner Caroline Leddy and producer Victoria Pile – and stars Mark Heap, Tamsin Greig, Stephen Mangan and Julian Rhind-Tutt. It focuses on soap opera-style twists and turns in the personal lives of the characters, portrayed in sketch-like scenes and sequences in which the film is slowed down or sped up, often emphasising the body language of the characters. The show had eight writers. Two series were made by the Talkback Thames production company for Channel 4.
The series ran between 3 September 2004 and 19 May 2006. One episode, filmed with the second series, was shown as a 90-minute-long special on 4 January 2007 in the UK, but was shown earlier in Australia and Belgium on 29 December 2006. Separate from the series, a sketch was made for Comic Relief and screened on 11 March 2005. Another was performed live at The Secret Policeman's Ball on 14 October 2006. On 29 April 2024, Green Wing returned as a six-part audio series released by Audible entitled Green Wing: Resuscitated.
== Synopsis ==
Green Wing's plot revolves around the lives of the staff of the East Hampton Hospital Trust, a fictional National Health Service (NHS) hospital with staff ranging from the slightly unusual to the completely surreal.
The series begins with a new arrival, surgical registrar Caroline Todd (Tamsin Greig). Caroline works alongside two other doctors: Guy Secretan (Stephen Mangan), an arrogant, half-Swiss, womanising anaesthetist, and "Mac" Macartney (Julian Rhind-Tutt), a suave, fashionable surgeon. Caroline soon develops feelings for both of them, though she is unsure as to which of the two she truly loves. Throughout the series, it becomes clear that Mac is her true love, but a range of misadventures prevent their relationship from flourishing. Other people Caroline meets include Martin Dear (Karl Theobald), a friendly house officer who is constantly failing his exams. He is unloved by his mother and is often bullied by Guy. Martin soon develops feelings for Caroline. There is also Angela Hunter (Sarah Alexander), a seemingly perfect, but irritating, senior registrar in pediatrics. Caroline dislikes Angela, but ends up taking her in as a lodger.
Caroline's main rival for Mac's affections is Sue White (Michelle Gomez), the staff liaison officer employed to listen and respond to the problems of East Hampton's staff. Sue is hostile and contemptuous towards everyone except Mac, whom she loves to the point of madness.
Alan Statham (Mark Heap) is an overbearing, stuttering and pedantic consultant radiologist. He is in a relationship with Joanna Clore (Pippa Haywood), the 48-year-old head of human resources, although she despises him. Their relationship is an open secret, with student doctor Boyce (Oliver Chris) often hinting at it when goading Alan. Joanna's staff include Kim Alabaster (Sally Bretton); Naughty Rachel (Katie Lyons); Harriet Schulenburg (Olivia Colman), an overworked mother of four trapped in an unhappy marriage; and Karen Ball (Lucinda Raikes), who is often bullied by Kim and Rachel.
== Creation ==
=== Writers and crew ===
Green Wing was devised, created and produced by Victoria Pile. She was also the casting director, one of the writers, and part of the editing, filming and post-production teams. She described Green Wing as "a sketch-meets-comedy-drama-meets-soap", and a continuation of her previous show, Smack the Pony, where Green Wing's crew also worked. Unusually for a British sitcom, which typically has only one or two writers, the show had eight: Pile, her husband Robert Harley, Gary Howe, Stuart Kenworthy, Oriane Messina, Richard Preddy, Fay Rusling and James Henry.
Pile and her co-writers initially used battery packs to represent characters, moving them around on her desk to develop scenarios for the show. The decision to make the characters doctors came later. Pile recalls that she mentioned to Peter Fincham that a hospital setting would work well and that he subsequently reported that Channel 4 were enthusiastic about a hospital location, which settled the matter. Even later still, a plot was developed and wall charts were used to mark up story arcs.
The show was directed and edited (along with Pile) by Tristram Shapeero and Dominic Brigstocke. Sketches were sped up or slowed down to create comic effect, often using body language to create humour. Editing was also used due to the amount of corpsing that occurred during the filming of the show. Tamsin Greig was said to corpse frequently, and episodes were written to minimise the contact between the characters of Caroline Todd and Alan Statham because Greig found it difficult not to laugh when acting alongside Mark Heap. The music, which features prominently in the show, was written by Jonathan Whitehead (under the name "Trellis") and won him an RTS Craft & Design Award.
=== Production ===
Following her success with Smack the Pony, Channel 4 gave Pile a fairly free hand with her next project. Their only requirement was that it should have enough of a narrative thread to make it more of a sitcom than a sketch show.
The show had a half-hour pilot made in 2002 that was never aired. Scenes from the pilot were used in the first episode, "Caroline's First Day", and can be spotted due to the characters' appearance, most notably Rhind-Tutt's haircut. The pilot allowed the writers to experiment, such as using different filming techniques. In the pilot, Doon Mackichan played Joanna Clore and was meant to play her in the original series, but left when she became pregnant.
Although each script was fully written, the actors were allowed to improvise their own jokes, frequently adding to what had already been written. Workshops were often used to allow actors to improvise their own material. One example of improvised material was Stephen Mangan's idea of Guy falling in love with Caroline. The show's crew also make appearances in the show as extras. For example, Pile's former assistant Phil Secretan (after whom Guy is named) appears at the end of a scene in the first episode. Henry appears in the background during Martin's exam in the episode, "Tests".
The filming was done at two hospitals, the Northwick Park Hospital in Middlesex and the North Hampshire Hospital in Basingstoke. This presented a problem because the show had to work around the real-life hospitals, with their actual doctors, patients and emergency situations. In one scene in the final episode in series one, Guy (Mangan) was hitting squash balls behind him, and nearly hit a patient. However, some scenes, such as those in Sue's and Alan's offices, were filmed in a studio. The pub in series two is filmed at the Foundation Beefeater in Fulwell, South West London.
Green Wing's title is said to have come from a small plastic green man with wings that was in executive producer Peter Fincham's top pocket, and fell on Pile's desk. Fincham claimed it was not his, so Pile kept it. This plastic man appears at the end of the credits on every show.
=== Unused storylines ===
Some plot lines written for Green Wing were never used. Unused storylines included Alan having an 80-year-old wife and step-grandchildren as old as him, and Guy suffering from impotence. Pile originally wanted the show to cover the entire hospital, not just doctors, but porters, car park attendants and kitchen staff. However, she decided that they had enough material with the eight main doctors and human resources workers.
Two endings were created for the special. The alternative ending is included on the DVD release of Green Wing, along with deleted scenes from the episode. The alternative ending was planned to be used if a third series was going to be commissioned, as this ending was much more ambiguous. Green Wing's cast preferred the alternative ending, but after some debate, it was not shown.
== Series summaries ==
=== Series 1 ===
Caroline arrives at East Hampton for her first day of work and meets her colleagues Guy and Mac. She is forced to spend her second day on the job quashing rumours that she slept with Guy after he put her up for the night. Failing junior doctor Martin soon falls in love with Caroline. Meanwhile, Alan and Joanna maintain their relationship, the worst kept secret in the hospital. Alan wants to shout their relationship from the rooftops, whereas Joanna wants more spontaneity and danger, so quickly turns her affections to Lyndon Jones (Paterson Joseph), the hospital's head of I.T.
Martin is revealed to be the son of Joanna Clore; she does not want anyone at the hospital to find out. Joanna briefly believes that she is pregnant once again, only to find out that the test results had been mixed up and it is in fact Harriet who is pregnant. Alan, elated by the thought that he may become a father, becomes obsessed with babies and suggests that they try for one when he finds out that Joanna is not pregnant. Joanna, bored of Alan's predictable behaviour, finally decides to end her relationship with him.
Caroline starts to get broody, but is unsure as to whether it is Mac or Guy that she loves. Sue White, staff liaison officer, is deeply in love with Mac, threatening to kill her love rivals. Both women are devastated to find that Mac is intending to move to Sheffield with his new girlfriend to take up a consultancy position. Before he leaves, Mac bets Guy that he would not be able to sleep with Joanna, so Guy picks her up at the leaving party. Caroline accuses Emily of being a fraudster, which turn out to be a misunderstanding, but Emily breaks up with Mac after he is amused rather than angered by Caroline's accusations. Mac and Caroline later kiss.
As they are about to leave, Caroline and Mac find out that there is an emergency at Guy's flat. Martin has discovered that Joanna is also Guy's birth mother. When Caroline and Mac arrive in an ambulance, Guy steals it in a drunken rage, with Mac and Martin in the back. Guy drives the ambulance to Wales, where, in an attempt to avoid a sheep, he drives onto a cliff edge. The series ends with the three of them balanced precariously on the cliff edge.
=== Comic Relief sketch (2005) ===
Mac fends off Sue's advances by saying he will only allow her to touch his arse if she can raise £10,000 for Comic Relief. Sue asks Martin, Joanna, Guy, and Alan for the money, which she eventually manages to raise, but Mac runs off before she can get hold of him.
=== Series 2 ===
Eight weeks after the incident with the ambulance, Mac is in a coma and Guy has been suspended from his job. During his coma, Sue steals some of Mac's semen and tries to make herself pregnant. At the end of the first episode, Mac wakes up, but with amnesia, which means he does not recall his nascent relationship with Caroline.
As Mac's memory returns, he and Caroline are on the verge of resuming their relationship when his former girlfriend Holly (Sally Phillips) returns to the hospital to replace Angela, who has left to pursue a career in television. Holly has a son, called Mackenzie, who she says is Mac's. Caroline distances herself from Mac and starts dating Jake Leaf (Darren Boyd), a complementary therapist. Sue then discovers that Holly is lying, that Mac is not her son's father after all. Holly leaves the hospital. Caroline, excited by the news, leaves Jake.
When Alan becomes unusually happy after winning an internet caption competition, Joanna seeks to destroy his good humour. Using her dwarf cousin (Big Mick), dressed up in green body paint, she plans to scare him. The plan backfires when Alan is so scared that he beats Joanna's cousin to death with a stuffed heron. Alan and Joanna throw the body into the incinerator, but become paranoid that they will be discovered. Alan, however, learns from Boyce that the death is being viewed as a suicide, so Alan and Joanna go on a rampage, thinking themselves above the law.
After the death of a patient known as "Yo-yo Man" who offers them wise advice, Guy, Mac and Martin all decide to propose to Caroline. She rejects Martin, considers the offer from Guy, and Mac appears to be unable to form a proposal. Mac then tells Caroline to meet him at the railway station for a weekend away, but then suddenly discovers that he is terminally ill, and rides off into the distance on his motorbike. Guy goes to the railway station where he finds that Caroline is now willing to accept his proposal. Meanwhile, in the HR department, Karen is sitting on a windowsill, believing that there are Clangers in the office. Whilst on the phone to a friend, Rachel opens the window, tipping Karen out in the process. As the day continues, no one seems to notice her absence.
The police arrive at the hospital. Alan and Joanna believe that they will be arrested, and with Boyce's help escape from the hospital in a stolen camper van. When they discover that Martin is hidden in the back of the van, Alan, panicking, drives into a field, and series two ends in the same way as series one, with the van hanging over the edge of a cliff.
=== Secret Policeman's Ball sketch (2006) ===
A sketch was performed for Amnesty International's Secret Policeman's Ball, with performances from Tamsin Greig, Stephen Mangan, Julian Rhind-Tutt and Michelle Gomez. Mangan and Rhind-Tutt appeared in two sketches.
When the announcer at the ball asks if there is a doctor in the house, Mac puts his hand up, to Caroline's embarrassment. Things get more embarrassing when Guy also volunteers, and asks why Caroline is sitting next to Mac when she is Guy's fiancée. An unconscious patient lies on an operating table. Guy touches her breasts, takes pictures of her naked body under the blanket, and kisses her. Caroline alleges that the patient is transgender, which repels Guy. Sue White then appears in a tutu, claiming that the patient is stalking Mac, and repeating the assertion that the patient is transgender.
=== Special ===
The episode begins with the funeral of Angela, who departed the show during the second series, and was later killed by a moose. Mac, after a month's leave, discovers what has happened between Caroline and Guy, and although hurt, makes no attempt to interfere. Guy, on learning of Mac's terminal illness, tells Caroline to marry Mac instead of him.
Meanwhile, Alan and Joanna are still on the run, having abandoned Martin. Whilst on their journey, they accidentally kill three more people, a mechanic, a shop assistant and a policeman. Soon, they decide that, with no transport, money or employment, the only option is suicide. They are last seen, naked, walking hand-in-hand towards the sea. Meanwhile, Karen returns to work after her fall, but has changed drastically. She has become more confident and has developed better dress sense. Boyce ends up missing Alan, after finding that his replacement will not tolerate any misbehaviour. With Joanna gone, the office girls start to run riot. They form their own tribe and become hostile to anyone who enters the department.
Mac and Caroline finally marry, despite Mac's terminal illness (the exact nature of which is never disclosed, although Mac does tell Guy that its name has an "a" and an "e" in it). Sue gets over her obsession with Mac and finds love with a new man, who reciprocates her feelings. The episode concludes with Caroline being carried into the air by a mass of helium filled balloons at the wedding reception. The DVD box set extras include an alternative ending where Guy and Mac grab onto Caroline's ankles and are taken to the sky with her; this alternative ending concludes with Mac saying, "Caroline, there's something I've been meaning to tell you."
=== Green Wing: Resuscitated ===
The revival is set 12 years after the original series ended. Caroline is now a medical pioneer in the USA, Guy has become a TV personality, and Mac has returned from several near-death experiences to continue working as a surgeon. Boyce has been promoted to head of radiology and Harriet is now head of human resources. Following their murder spree Joanna is now in prison, while Statham's lawyers got him a reduced sentence involving psychiatric care, and he is now working under Boyce. Sue is still working as the staff liaison officer and Martin has still not qualified as a doctor.
== Cast ==
=== Main characters ===
=== Recurring characters ===
Darren Boyd – Jake Leaf
Keir Charles – Oliver
Daisy Haggard – Emmy
Paterson Joseph – Lyndon Jones
Sally Phillips – Holly Hawkes
== Critical reaction ==
The show received generally very positive reviews. The Evening Standard said that it was "a comedy as physically adroit as it was verbally sharp," and The Guardian said that "Channel 4’s hospital sitcom is the most innovative comedy since, well, The Office." In 2006, Kathryn Flett of The Observer voted it one of the top ten TV programmes of the year. In Broadcast Magazine, the second series was voted joint-second best comedy series in 2006. In South Africa, where Green Wing was broadcast on BBC Prime, The Sunday Times of South Africa voted the show the best DStv programme of 2007. Composer Daniel Pemberton wrote that the soundtrack to Green Wing was, "One of the most innovative TV soundtracks in recent years."
Criticisms of Green Wing include the lazzi methods of filming and the overall length of the episodes, with some critics claiming that hour-long episodes are too long. The show won the 2005 and 2006 Comedy Tumbleweed Awards for "Worst Camerawork." Some were also critical of what was seen as a decline in quality when the second series began. Cathy Pryor in The Independent on Sunday said that, "Sadly, though, since I'm something of a fan, I have to report that the first episode of the second series is, disappointingly, rather flat. To be fair, there were a couple of laugh-out-loud moments - Dr Statham banging his head and falling down being one of them - but the whole [thing] didn't quite gel. Or should that be coagulate? I'll stop making bad jokes now since I'm still not as funny as anyone in the show. But I sincerely hope that the opener is a one- off and not a sign that Green Wing is going down the pan."
Similar comments were made by A. A. Gill. When the first series was broadcast, he praised the cast and characters, but commented negatively on the filming style and dramatic qualities. He also said:
"...it was one of the most freshly funny and crisply innovative comedies for years. The humour was all based in the character, not the situation. The story lines were negligible; there were no catch phrases; it was surreal in a way we hadn’t seen since Monty Python; and the cast were actors being funny from inside a characterisation, not stand-up comics bolting a cartoon persona onto the back of gags."
Subsequently, Gill critiqued the first episode of series two, in particular the use of a dream sequence at the beginning of the episode. He wrote,
"Now, every 11-year-old knows dream sequences are the lowest form of plotting solution, lower than unexplained superpowers such as the ability to stop time or become invisible; even lower than a magic get-better potion. Within two minutes, Green Wing had destroyed itself, lost its assured grip on the cliff of comedy and tumbled into the abyss of embarrassing overacting, formless gurning and pointless repetition. What had once looked Dada-ishly brilliant now looked like stoned improv from a show-off's drama school. The lack of plot and coherent narrative that previously had been a blessed freedom was revealed to be a formless free-for-all, brilliant performances as silly mannerisms. Nothing I've seen this year has disappointed me as sharply as the second series of Green Wing. As Tom Paine so poignantly pointed out, only a step separates the sublime from the ridiculous."
The rest of the series received some praise and, in a 2009 article, Gill–– writing about the current comedy output at the time–– said: "Show me a funny indigenous comedy series; show me one that has been made in the past five years, other than Green Wing."
== Media ==
=== DVDs ===
=== Books ===
The first series scripts were released as Green Wing: The Complete First Series Scripts in paperback on 22 October 2006 (ISBN 1-84576-421-8) by Titan Books. The book contains bonus material made exclusively for the book and previously unseen photos.
=== Soundtrack ===
The soundtrack, entitled Green Wing: Original Television Soundtrack, was released by Silva Screen on 8 October 2007. It contains 23 tracks of the best of Jonathan Whitehead's Original Music created for the show.
=== Online viewing ===
The complete series is available on Channel 4 on Demand.
== Awards and nominations ==
Green Wing won the first BAFTA Pioneer Audience Award in 2005. This is the only BAFTA award that is voted on by the general public. Pippa Haywood won the 2005 Rose d'Or for "Best Female Comedy Performance". Tamsin Greig won an award at the RTS Awards in 2005 for "Best Comedy Performance". Jonathan Whitehead won "Best Original Score" at the RTS Craft & Design Awards 2005. Greig received a BAFTA nomination for Best Comedy Performance in 2005, losing to David Walliams and Matt Lucas.
Green Wing also won a number of The Comedy.co.uk Awards, including the "Comedy of the Year" award in 2006.
== Possible spin-off ==
A third series of Green Wing was not made, due to scheduling difficulties with the cast and crew undertaking new projects, and a lack of budget at production company talkbackTHAMES. However, creator Victoria Pile mentioned in a 2007 interview in the Radio Times that she may create a spin-off, saying, "I'm hoping to do another Channel 4 comedy imminently, possibly starring some of the same cast. Hopefully, it will be some kind of spin-off from Green Wing."
In 2009, Pile and most of the writing team behind Green Wing created a sitcom pilot set at a university, entitled Campus, which featured similar concepts to Green Wing, including improvisation. The motto of the university was "with wings," a reference to the show. The pilot was broadcast as part of Channel 4's Comedy Showcase. A full series began in 2011, but was cancelled after one series.
== Impact ==
A cocktail called the Green Wing was served at the 2005 BAFTAs. It was made using vodka, cloudy apple juice, elderflower cordial, and sparkling mineral water. A Green Wing convention called "Wingin' It" was organised to raise money for Great Ormond Street Hospital, and took place on 13 January 2007 at the Brook Green Hotel, Hammersmith. There was a special appearance by Green Wing cast at the British Film Institute, on 17 January 2007; Pile, Greig, Mangan, and Rhind-Tutt appeared. Some of the other writers, as well as Theobald and Heap, were in the audience. The event was hosted by John Lloyd. Green Wing appeared in an episode of the BBC documentary series Imagine, entitled A Funny Thing Happened on the Way to the Studio. Some of the funeral scenes from the special were shown, and the presenter of the show, Alan Yentob, appeared as one of the mourners.
== References ==
== External links ==
Green Wing on Channel 4
Green Wing at the British Film Institute
Green Wing at IMDb
Green Wing at British Comedy Guide | Green Wing is a British sitcom set in the fictional East Hampton Hospital. It was created by the same team behind the sketch show Smack the Pony – Channel 4 commissioner Caroline Leddy and producer Victoria Pile – and stars Mark Heap, Tamsin Greig, Stephen Mangan and Julian Rhind-Tutt. It focuses on soap opera-style twists and turns in the personal lives of the characters, portrayed in sketch-like scenes and sequences in which the film is slowed down or sped up, often emphasising the body language of the characters. The show had eight writers. Two series were made by the Talkback Thames production company for Channel 4.
The series ran between 3 September 2004 and 19 May 2006. One episode, filmed with the second series, was shown as a 90-minute-long special on 4 January 2007 in the UK, but was shown earlier in Australia and Belgium on 29 December 2006. Separate from the series, a sketch was made for Comic Relief and screened on 11 March 2005. Another was performed live at The Secret Policeman's Ball on 14 October 2006. On 29 April 2024, Green Wing returned as a six-part audio series released by Audible entitled Green Wing: Resuscitated. | 9 |
355 | mac | It's Always Sunny in Philadelphia (wikipedia) | It's Always Sunny in Philadelphia is an American sitcom created by Rob McElhenney and developed with Glenn Howerton for FX. It premiered on August 4, 2005, and was moved to FXX beginning with the ninth season in 2013. It stars Charlie Day, Howerton, McElhenney, Kaitlin Olson, and Danny DeVito. The series follows the exploits of "The Gang", a group of narcissistic and sociopathic friends who run the Irish dive bar Paddy's Pub in South Philadelphia, Pennsylvania, but spend most of their free time drinking, scheming, arguing among themselves, and plotting elaborate cons against others, and at times each other, for personal benefit, financial gain, revenge, or simply due to boredom or inebriation.
With its fifteenth season, the series became the longest running live-action American sitcom, and the longest running series ever on cable TV surpassing The Adventures of Ozzie and Harriet, which ran for 14 seasons (435 episodes) between 1952 and 1966. In December 2020, the series was renewed for a total of four additional seasons, bringing it to 18 seasons. The sixteenth season premiered on June 7, 2023. The show has received critical acclaim, with many lauding the cast performances and dark humor. It has amassed a large cult following.
== Plot ==
The series follows a group of misfit, narcissistic sociopaths, referred to as "The Gang", who run a meager, unsuccessful Irish bar called Paddy's Pub in the neighborhood of South Philadelphia. The Gang originally consisted of janitor Charlie Kelly (Charlie Day), bouncer Mac (Rob McElhenney), and bartender Dennis Reynolds (Glenn Howerton), the three of whom own Paddy's Pub, in addition to Dennis' twin sister Dee Reynolds (Kaitlin Olson), a struggling actress who works as a waitress there. In the second season, they are joined by Frank Reynolds (Danny DeVito), an eccentric millionaire and the neglectful father of the Reynolds twins, who takes over most of the ownership of the bar. He soon becomes the financial catalyst for the Gang, often funding many of the Gang's over-complicated plots, while simultaneously succumbing to the brazen depravity of the group.
Each member of The Gang exhibits unethical behavior and anti-social traits such as extreme selfishness, pathological dishonesty, narcissism, physical and emotional aggression, excessive drinking and substance abuse, unregulated emotions, cruelty, greed, misogyny, manipulative tendencies, predatory behavior, jealousy, sociopathy, apathy toward suffering, emotional detachment, frequent abuse of the legal system, exploitation, discrimination against disability, race, and appearance, rudeness and contempt to others, and absolutely no regard for the people around them, while also displaying acute codependency, stupidity, negligence, and a surprising lack of awareness of basic social norms. The comedy of the show emerges from these extreme character traits resulting in conflicts that lead The Gang into absurd, dark, and painfully embarrassing situations, typically ending with them getting their comeuppance, but never learning their lesson. This allows the show to mine a variety of socio-political and economic issues for satire and dark humor while keeping the characters in a state of relative stasis conducive to the long-running sitcom format.
Episodes usually find The Gang hatching elaborate schemes and regularly conspiring, against both outsiders and one another, for personal gain, revenge, or simply schadenfreude. They habitually inflict physical and psychological pain on anyone who crosses their path, even each other, yet always return to the status quo at Paddy's Pub because they have alienated the rest of society and have only each other's company in the end. The Gang has no sense of shame when attempting to get what they want and often engages in activities that others would find humiliating, disgusting, or shocking. Some of these situations include pretending to be disabled, becoming addicted to crack cocaine in order to qualify for welfare, attempted cannibalism, kidnapping, waterboarding, blackface, blackmail, stalking, grave robbing, hiding naked inside a couch to eavesdrop on people, tricking a man into giving his daughter a lap dance, foraging naked in the sewers for rings and coins, impersonating police officers to extort civilians, creating a cult, secretly feeding someone their dead pet, plugging their open wounds with trash, setting an apartment full of people on fire and nailing the exit shut, taking out life insurance on a suicidal person, and lying about having AIDS in order to get priority access to water park rides. In an angry summation of their circumstances during one such escapade, Dennis laments The Gang's dynamic:
We immediately escalate everything to a ten... somebody comes in with some preposterous plan or idea, then all of a sudden everyone's on the gas, nobody's on the brakes, nobody's thinking, everyone's just talking over each other with one idiotic idea after another! Until, finally, we find ourselves in a situation where we've broken into somebody's house – and the homeowner is home!
With rare exceptions, Paddy's Pub generates limited revenue. Most stay away from the establishment due to the numerous stabbings that have taken place. The few regular customers have been known to serve themselves. The Gang has been known to close Paddy's for extended periods without warning. When the bar is open, they shirk their respective jobs' responsibilities and choose to drink instead. Paddy's is only able to stay in business because of Frank's financial backing, government bailouts and tax fraud.
== Cast and characters ==
The show features a core cast of five characters (The Gang) and a recurring cast of colorful side characters, including the Waitress, Cricket, the McPoyles, the Ponderosas, the Lawyer and various family members like Mrs. Kelly, Mrs. Mac and Uncle Jack Kelly, who cross paths and interact with the Gang in increasingly unhinged ways as the show progresses.
=== Main ===
Charlie Day as Charlie Kelly, co-owner and janitor of Paddy's Pub. He is a childhood friend of Mac, and high school friend of Dennis and Dee. He lives in squalor with Frank in a run-down, vermin-infested apartment, and has deep-seated psychological problems, partly due to substance abuse from huffing paint and glue, and partly due to his complicated family background possibly involving child abuse. He has an extensive history of pica and regularly eats various items not meant for human consumption, such as cat food, stickers, paint, and bleach. Due to his general lack of intelligence and his illiteracy, he is arguably the simplest member of The Gang. Despite this, Charlie is a naturally gifted musician, a self-proclaimed expert in "bird law" and possibly the only competent worker at Paddy's with his knack for unorthodox maintenance practices ("Charlie Work"). He also has an unhealthy obsession with "The Waitress", a recurring character who finds his interest in her creepy.
Glenn Howerton as Dennis Reynolds, co-owner and the main bartender of Paddy's Pub, in addition to being Dee's twin brother and Frank's son. Originally the most intelligent and normal-seeming of the three co-owners, Dennis is slowly revealed to be the most narcissistic and psychopathic of The Gang. Dennis is extremely superficial, selfish, vain and abrasive. His predatory nature is often depicted through numerous attempts to seduce various women; which, when successful, result in him gaslighting and emotionally abusing them in order to win over their favor before inevitably dumping them once he has had sex with them ("The D.E.N.N.I.S. System"). It is strongly hinted at times that Dennis may secretly be a serial killer, though this remains ambiguous as a running gag. In season 10, he is diagnosed with borderline personality disorder, though he frequently denies this and believes himself to be completely rational, and is convinced that he is in complete control of everything and everyone around him, going as far as to label himself a 'golden god'. In the season 12 finale, Dennis reveals to the rest of the gang that he has an infant son, and moves to North Dakota to raise him. He returns to Philadelphia in season 13, supposedly supporting his family from a distance.
Rob McElhenney as Ronald "Mac" McDonald, co-owner and self-proclaimed bouncer of Paddy's Pub. He is Charlie's childhood friend and Dennis's high school friend. The son of a convicted felon who has been in prison for much of Mac's life, he frequently attempts to demonstrate his toughness and refers to himself as the "sheriff of Paddy's". Deeply insecure, Mac constantly seeks the approval of those around him, especially his father, his apathetic and emotionally absent mother, and Dennis, his roommate. He suffers from extreme bouts of body dysmorphia, and has been depicted at various weights throughout the course of the series: prior to the beginning of Season 7, he gained 60 pounds (27 kg) and was diagnosed with Type 2 diabetes, and when he finally returned to a healthy weight in the following season, he admitted he misses being fat, as he believed he had come across as "scary" to people. In Season 13, he is noticeably fit and physically stronger, though it is quickly revealed his motives for attaining his shape was strictly due to his intense desire for acceptance from the rest of the Gang. He often brags about his hand-to-hand combat skills, but typically flees from physical confrontation and is usually depicted as the most cowardly of the gang. Mac is a Roman Catholic, though he often espouses strong Christian fundamentalist opinions, despite his often amoral behavior, such as casual sex with numerous women, including Dennis's and Dee's mother. Though it is frequently insinuated Mac harbors homosexual feelings, he maintained an adamant denial of any such proclivity, much to the gang's annoyance, until he comes out in season 12. Later episodes reveal that Mac is sexually attracted to his best friend, Dennis.
Kaitlin Olson as Deandra "Sweet Dee" Reynolds, waitress and sometimes bartender at Paddy's Pub, as well as Dennis's twin sister and Frank's daughter. Though initially depicted as The Gang's 'voice of reason' in the debut season, she gradually loses any sense of moral fortitude that she once had, and is frequently shown to be just as prejudiced and depraved as her male friends by the end of season 1, arguably becoming the most petty member of the group, often plotting against others whom she deems more successful than herself in a vain effort to boost her own image. Dee wore a back brace in high school, leaving her with the nickname "The Aluminum Monster", and she is frequently referred to by the gang as a bird. Dee lives alone in an apartment. Though often the butt of the gang's jokes, she frequently involves herself in their schemes, perhaps due to her constant need for approval and attention from her peers. She does not hold any ownership stake in the bar – perhaps due to the gang's various prejudices against her, but also in part to her desire to become a professional actress/comedian (an ambition she consistently fails to achieve due to her debilitating stage fright and her general lack of any apparent talent). In multiple episodes, it is referenced that Dee set her college roommate on fire, and she is often portrayed as the most physically violent of the group. Despite expressing outward disgust at her brother's more predatory behavior, later episodes reveal Dee not to be above such behavior herself.
Danny DeVito as Frank Reynolds, legal father of Dennis and Dee Reynolds, and the majority owner of Paddy's Pub soon after his introduction in season 2 onward. Frank is a millionaire and often funds and enables The Gang's worst schemes and impulses, just to feel a sense of youthfulness and energy. He was once a successful businessman with a long history of illegal operations and dealings with sordid characters, but chooses to abandon that life and redeem himself after leaving his "whore wife", Barbara Reynolds. It is revealed at the end of season 2 that Dennis and Dee are products of an affair and not actually his biological children. He has since embraced his "feral" nature and describes himself as "fringe class". Despite his substantial financial resources, he chooses to share a decrepit studio apartment with Charlie, where they sleep together on a pullout couch and have a surprisingly affectionate pseudo-father/son relationship. The two have similar interests, such as playing the inexplicable game of Night Crawlers and foraging naked in sewers for valuables. He always arms himself with at least one loaded handgun and does not hesitate to brandish or even discharge one when provoked, and often snorts cocaine as part of his daily routine.
== Production ==
Charlie Day, Glenn Howerton, and Rob McElhenney first met each other while auditioning for Tuck Everlasting and other projects in New York City and, later, in Los Angeles—they were going up for similar parts, moved to Los Angeles around the same time and even had the same manager Nick Frenkel. Day and Howerton, notably, got to know each other on a car ride back from testing for That '80s Show in late 2001, when Howerton was cast as Corey Howard and Day did not get the part of his best friend. While living in New York, Day had been making comedic home movies with his friends from the Williamstown Theatre Festival—Jimmi Simpson, Nate Mooney, David Hornsby and Logan Marshall-Green, (many of whom would later go on to be involved with Sunny)—which inspired McElhenney and Howerton to want to make short films of their own with him. McElhenney, in particular, had been writing screenplays between jobs and since none of them were picked up, decided to shoot them himself with Howerton, Day and other actor friends. The decision to make their own short films was further influenced by the release of the affordable Panasonic DVX100A digital camera as well as the accessible, low-budget look of The Office (UK) and Curb Your Enthusiasm.
It's Always Sunny in Philadelphia grew out of an idea for a short film conceived late one night by McElhenney "where a friend came over to another friend's house to get sugar, and the friend tells him he has cancer, and all the guy can think about is getting his sugar and getting out of there". He wrote the scene down before taking it to Howerton the next day to flesh it out and work on making it comedic. Day was soon roped in and the first script was written, featuring three struggling actors in LA named Charlie, Glenn and Mac, and the ensuing awkwardness around Charlie's cancer diagnosis. The home movies were shot and reshot multiple times, initially with Hornsby playing the Mac character and McElhenney behind the camera as director. It was via this process that McElhenney, Day and Howerton learned the basics of shooting, editing and other aspects of film-making. The three then developed a second "episode" of their home movie series, this time focused on the humor from Mac's sense of shame around his relationship with Carmen, a transgender woman. At this point, it became clear that the home movies had potential as a television series, instead of the short films they were envisioned as originally. Both parts would eventually end up in the episode "Charlie Has Cancer".
The home movie was titled It's Always Sunny on TV after the a-ha song "The Sun Always Shines on T.V.". Howerton had been listening to the album Hunting High and Low (1985) while stretching at a Crunch gym in West Hollywood. This was then developed into a pilot called It's Always Sunny on TV and was shot on a digital camcorder and filmed in the actors' own apartments. They expanded the central cast to four people living in Los Angeles, "a group of best friends who care so little for each other", Howerton said.
It was believed the pilot was shot with a budget of just $200, but Day would later comment, "We shot it for nothing... I don't know where this $200 came from... We were a bunch of kids with cameras running around shooting each other and [the] next thing you know, we're eleven years in and we're still doing the show." This pilot was shopped by the actors around various studios, their pitch being simply showing the DVD of the pilot to executives. After viewing the pilot, FX Network ordered the first season. The show was budgeted at $450,000 an episode, less than a third of a network standard, using Panasonic's DVX100 MiniDV prosumer video camera. The original concept had "the gang" being out-of-work actors with the theme song being a cha-cha version of "Hooray for Hollywood"; however there were too many shows at the time with a similar premise. "The network came to us and said, 'We don't want a show about actors,' and we said, 'Fine, let's put it somewhere else,'" McElhenney explained. "I'm from Philly, let's put it in Philly, and we'll make it about a bar, because that's a job where you can have lots of free time and still have income that could explain how these people can sustain themselves." The title was later changed to reflect that, in the unaired pilot, the gang had been rewritten as bar owners in Philadelphia, instead of actors in LA. Prior to Kaitlin Olson joining the show, the character Sweet Dee was going to be played by Jordan Reid, who at the time was the girlfriend of McElhenney. The part was recast after they broke up.
After the first season, FX executives were worried about the show's low ratings and demanded that changes be made to the cast. "So, John Landgraf, who's the president of FX, he called me in for a meeting and was like, 'Hey, no one's watching the show, but we love it,'" McElhenney recalled. "'We wanna keep it on, but we don't have any money for marketing, and we need to add somebody with some panache that we can hopefully parlay into some public relations story, just so we can get people talking.'" FX began suggesting actors such as Danny DeVito that could boost the show's profile. "It's not that we were reticent to the idea of adding Danny to the show," Howerton recalled, "It's that we were reticent to add a name to the show. You know, because we kinda liked that we were no-names and it was this weird, small thing, you know." Initially, McElhenney refused, saying "No, I just don't think we wanna do that, and they were like, 'Oh OK, well, you know... the show's over.'" Realizing they needed to change the trajectory of the show to please the network, McElhenney, Howerton, and Day became open to adding a new cast member who was familiar to the public. However, McElhenney, Howerton, and Day were hesitant at first since they thought they would "ruin the show", but during an interview, Day commented on how they got lucky with DeVito in the end: "We didn’t know what Danny would be like as a person. It turned out he was as great an actor as he was a person. As I said, we got lucky with Danny." DeVito joined the cast in the first episode of the second season, playing the father of Dennis and Dee.
The show is shot in both Philadelphia and Los Angeles. The exterior of Paddy's Pub is located at the Starkman Building on 544 Mateo Street in Los Angeles. On April 1, 2016, the series was renewed for a thirteenth and fourteenth season, which matched The Adventures of Ozzie and Harriet with the most seasons for a live-action sitcom in American television history. In January 2023, McElhenney confirmed that filming for the sixteenth season had begun. In May 2024, DeVito said that the seventeenth season would begin filming in September 2024.
== Episodes ==
== Broadcast and syndication ==
The first season ran for seven episodes with the finale airing September 15, 2005. According to McElhenney, word of mouth on the show was good enough for FX to renew it for a second season, which ran from June 29 to August 17, 2006. Reruns of edited first-season episodes began airing on FX's then-parent network, Fox, in June 2006, for a planned three-episode run—"The Gang Finds a Dead Guy," "Gun Fever" (which was renamed "Gun Control") and "Charlie Gets Molested" were shown. The show was not aired on broadcast television again until 2011, when FX began offering it for syndication.
The third season ran from September 13 to November 15, 2007. On March 5, 2008, FX renewed It's Always Sunny in Philadelphia for a fourth season. On July 15, 2008, it was reported that FX had ordered 39 additional episodes of the series, produced as seasons five through seven of the show. All five main cast members were secured for the entire scheduled run. The fifth season ran from September 17 to December 10, 2009. On May 31, 2010, Comedy Central began airing reruns. WGN America also began broadcasting the show as part of its fall 2011 schedule.
The sixth season ran from September 16 to December 9, 2010, comprising 12 episodes, plus the Christmas special. The seventh season ran from September 15 to December 15, 2011, comprising 13 episodes. On August 6, 2011, FX announced it had picked up the show for an additional two seasons (the eighth and ninth) running through 2013. On March 28, 2013, FX renewed the show for a tenth season, and announced that it would move to FX's new sister network, FXX.
In April 2017, Kaitlin Olson announced that It's Always Sunny in Philadelphia would go on an extended hiatus. In an interview with TV Guide, she said, "We ended up pushing our next season a year because we were all busy with separate projects this year. So at the end of this coming shooting season of The Mick, I'll step right into Sunny after that." On October 2, 2017, the show premiered on Vice on TV.
The series is available for streaming on Hulu except for the episodes "America's Next Top Paddy's Billboard Model Contest", "Dee Reynolds: Shaping America's Youth", "The Gang Recycles Their Trash", "The Gang Makes Lethal Weapon 6" and "Dee Day", due to scenes involving blackface. The same episodes are missing from Netflix in the UK, Disney+ in Australia, Canada, and Scandinavia, and Star+ in Latin America.
== Music ==
The show uses recurring orchestral production music selections. "We had a music supervisor called Ray Espinola and we said, 'Give us everything you have in a sort of Leave It to Beaver with a big band-swing kind of feel,' and the majority of the songs are from what he sent over," Charlie Day explained. "When you set it against what these characters were doing—which often times can be perceived as quite despicable, or wrong—it really disarmed the audience. It just became our go-to library of songs."
The theme song is called "Temptation Sensation" by German composer Heinz Kiessling. Kiessling's work ("On Your Bike" and "Blue Blood") can also be heard during various scene transitions throughout the show, along with other composers and pieces such as Werner Tautz ("Off Broadway"), Joe Brook ("Moonbeam Kiss"), and Karl Grell ("Honey Bunch"). Many of the tracks heard in the series are from Cafe Romantique, an album of easy listening production music collected by Extreme Music, the production music library unit of Sony/ATV Music Publishing. Independent record label Fervor Records has also contributed music to the show. Songs from The Jack Gray Orchestra's album Easy Listening Symph-O-Nette ("Take A Letter Miss Jones," "Golly Gee Whiz," and "Not a Care in the World") and the John Costello III release Giants of Jazz ("Birdcage," "Cotton Club" and "Quintessential") are heard in several episodes. The soundtrack, featuring most of the music heard on the show, was released in 2010.
=== Soundtrack track listing ===
== Reception and legacy ==
=== Critical reviews and commentary ===
It's Always Sunny in Philadelphia has received critical acclaim for its humor and the performances of the cast. Emily Nussbaum of The New Yorker praised the show, calling it "not merely the best sitcom on television but one of the most arresting and ambitious current TV series, period." Gillian Flynn of Entertainment Weekly reviewed the first season negatively, commenting, "[I]t is smug enough to think it's breaking ground, but not smart enough to know it isn't." Brian Lowry of Variety gave the first season a positive review, saying it was "invariably clever and occasionally a laugh-out-loud riot, all while lampooning taboo topics." However, later seasons of the show have received favorable ratings on review aggregator Metacritic, receiving 70/100, 78/100 and 85/100 for seasons 4, 5 and 6 respectively. The show has become a cult hit with viewers and is often compared in style to Seinfeld—particularly due to the self-centered nature of its main characters. The Philadelphia Inquirer reviewer Jonathan Storm wrote, "It's like Seinfeld on crack," a quote that became widely used to describe the series, to the point that FX attached the tagline, "It's Seinfeld on crack."
In 2014, Entertainment Weekly listed the show at number 7 in the "26 Best Cult TV Shows Ever," with the comment that "it's a great underdog story ... If it sounds too dark for you, consider that there's an episode about making mittens for kittens, and it's adorable." In 2016, a New York Times study of the 50 TV shows with the most Facebook likes found that Sunny was "more popular in college towns (and most popular in Philadelphia)." In 2015, Rolling Stone rated the top 20 greatest and funniest It's Always Sunny in Philadelphia episodes, stating "for 10 seasons, the series had mined comic gold from the execrable behavior of the owners of Paddy's Pub." They claimed the two-part season 4 episode, "Mac and Charlie Die" is the sitcom's greatest episode yet. In 2019, the BBC called the show "the best US sitcom." They praised the show's unique outlook and ability to range from nihilistic humor to genuine heartfelt moments. According to Matt Fowler of IGN, the series "broke new ground" due to its sociopathic depiction of "The Gang". It was also ranked 63rd in IGN's list of the top 100 TV shows of all time.
=== Awards ===
== Other media ==
=== The Nightman Cometh live ===
In September 2009, the cast took their show live. The "Gang" performed the musical The Nightman Cometh in New York City, Boston, Seattle, San Francisco, Los Angeles, and Philadelphia. Mary Elizabeth Ellis and Artemis Pebdani also appeared in the performance as The Waitress and Artemis. Actress Rhea Perlman (wife of Danny DeVito) assumed the role of Gladys. Creator Rob McElhenney said that Live Nation originally approached the cast about doing the show at 30 cities, but in the end the cast settled on six. Co-developer Glenn Howerton described the show as "essentially an expanded version of the actual episode of "The Nightman Cometh," which was the final episode for season four. There are some added moments, added scenes, added songs, and extended versions of songs that already existed." The performance featured two new songs, and the actors were given more opportunity to improvise thanks to the longer running time. An episode from season five was also previewed before the show. The Los Angeles performance, filmed at The Troubadour, was included as a bonus feature on the season four DVD box set.
=== Russian adaptation ===
A Russian adaptation of It's Always Sunny in Philadelphia premiered in Russia on the television channel TNT on May 12, 2014. This version is titled В Москве всегда солнечно (V Moskve vsegda solnechno, It's Always Sunny in Moscow) and like the original, centers around four friends, who own a bar called "Philadelphia" in Moscow.
=== Book ===
A book based upon It's Always Sunny in Philadelphia was released on January 6, 2015, titled The Gang Writes a Self-Help Book: The 7 Secrets of Awakening the Highly Effective Four-Hour Giant, Today.
=== Podcast ===
On November 9, 2021, Howerton, Day, and McElhenney started The Always Sunny Podcast, an episode-by-episode rewatch podcast, with Megan Ganz as producer. Occasional guest stars include Kaitlin Olson, David Hornsby, Mary Elizabeth Ellis, Michael Naughton, Lin-Manuel Miranda, Cormac Bluestone and Danny DeVito.
== Notes ==
== References ==
== External links ==
Official website
It's Always Sunny in Philadelphia at IMDb | It's Always Sunny in Philadelphia is an American sitcom created by Rob McElhenney and developed with Glenn Howerton for FX. It premiered on August 4, 2005, and was moved to FXX beginning with the ninth season in 2013. It stars Charlie Day, Howerton, McElhenney, Kaitlin Olson, and Danny DeVito. The series follows the exploits of "The Gang", a group of narcissistic and sociopathic friends who run the Irish dive bar Paddy's Pub in South Philadelphia, Pennsylvania, but spend most of their free time drinking, scheming, arguing among themselves, and plotting elaborate cons against others, and at times each other, for personal benefit, financial gain, revenge, or simply due to boredom or inebriation.
With its fifteenth season, the series became the longest running live-action American sitcom, and the longest running series ever on cable TV surpassing The Adventures of Ozzie and Harriet, which ran for 14 seasons (435 episodes) between 1952 and 1966. In December 2020, the series was renewed for a total of four additional seasons, bringing it to 18 seasons. The sixteenth season premiered on June 7, 2023. The show has received critical acclaim, with many lauding the cast performances and dark humor. It has amassed a large cult following. | 8 |
356 | mac | List of Foster's Home for Imaginary Friends characters (wikipedia) | This is a list of characters from the Cartoon Network animated television series Foster's Home for Imaginary Friends.
== Main characters ==
=== Mac ===
Mac (voiced by Sean Marquette) is Terrence's younger brother who is a bright, shy, and creative eight-year-old boy and Bloo's creator who visits Foster's every day. Mac is often the voice of reason among his friends when they are making decisions. However, his extremely good nature tends to make him somewhat naive. He is very attached to Bloo and it is shown that his biggest fear is never seeing him again, because Bloo is what keeps him happy and cheerful and vice versa. Mac becomes hyperactive to the point of a rabid mania when he eats sugar. Once in this state, he becomes impossible to control, will often become obsessed with seeking any other source of sugar. He, alongside Bloo, made a cameo appearance in The Powerpuff Girls series finale, "The Powerpuff Girls Rule!".
=== Bloo ===
Blooregard "Bloo" Q. Kazoo (voiced by Keith Ferguson) is Mac's best friend and imaginary friend, Bloo is a blue-colored friend who resembles as a dome cylinder not unlike a bollard with two eyes. He is often very immature, happy-go-lucky, self-centered and egotistical as well as having a knack for getting in trouble and prone for doing kid's and children's antics. Despite all this, he still has a good heart and apologizes for his jealousy. Bloo loves paddle-balls and toys even though he cannot make the ball hit the paddle. His full name is Blooregard Q. Kazoo. He, along with Mac, made a cameo appearance in The Powerpuff Girls series finale, "The Powerpuff Girls Rule!".
=== Wilt ===
Wilt (voiced by Phil LaMarr) – A very tall, friendly and incredibly nice imaginary friend with only a right arm and a crooked left eye-stalk. However, in "Good Wilt Hunting", it is discovered that he was not always this way; he was injured during a basketball game, leaving his left eye crushed and his left arm injured. Wilt exhibits consummate good sportsmanship, which he applies to every part of life he can. He is considered the nicest person at Foster's and is known for being excessively polite and apologetic; this is often taken advantage of by the other imaginary friends. Wilt has a big heart, is frequently cool and collected, and, only on very rare occasions shows anger at all, at which point, he will express his anger in overdramatic hysterics. According to the episode "Room with a Feud", among him, Coco and Eduardo, he has been in the house for the longest time. He is named after basketball legend Wilt Chamberlain.
=== Eduardo ===
Eduardo (voiced by Tom Kenny) is a big, hairy and purple Spanish-speaking imaginary friend who resembles a mixture of a minotaur and one of the beasts from Maurice Sendak's storybook, Where the Wild Things Are with horns, a snout, a pointy demon-like tail and large teeth. Despite his large size, overwhelming strength, and menacing demeanor, Eduardo is usually docile, timid and has a somewhat overly sensitive nature, crying at minor negative occurrences, and being scared of almost everything. However, he can be ferocious if angered or in the circumstance that danger befalls his friends. Eduardo has a fondness for potatoes, dogs, and his cuddly toys. His creator, Nina Valerosa, created him to protect her in a rough neighborhood and is now a police officer.
=== Coco ===
The Coco Bird (voiced by Candi Milo) is a chicken-like imaginary friend with a palm tree for a head, a crooked red beak and an aeroplane-like body who can only say her name at various speeds and different emphases. A talent unique to her is her ability to lay colorful eggs containing a plethora of objects. Mac, Bloo, Eduardo, Frankie, Wilt, and others usually understand her when she speaks, and often translate for her. Despite her appearance and quirky behavior, she can demonstrate a perceived intelligence, principle and kindness. No one knows who her creator is as she was found on a South Pacific island by two scientists named Adam and Douglas.
=== Frankie Foster ===
Frankie Foster (voiced by Grey DeLisle) is Madame Foster's redheaded 22-year-old granddaughter, addressed as "Miss Francis" by Mr. Herriman. Her parents are never seen in the series. Frankie is the caregiver at Foster's and helps keep everything in order. In spite of Mr. Herriman's fussiness and fixation with rules and cleanliness, she is usually very friendly, outgoing and laid-back. According to her driver's license in "Bus the Two of Us", she was born on July 25, 1984. Frankie is friends with most of the imaginary friends at Foster's (particularly Wilt, Eduardo, Coco, and Bloo) and can be described as a protective big sister to them, but sometimes gets unsuccessfully annoyed at Bloo, Mac, Cheese, Madame Foster and Mr. Herriman.
=== Mr. Herriman ===
Mr. H. Herriman (voiced by Tom Kane) is a gray and white, large, elderly, anthropomorphic, lop-eared and rabbit-like British accented imaginary friend imagined by Madame Foster, in fact, quite similar to Bruce Wayne's butler, Alfred Pennyworth. He wears a tailcoat, white gloves and a top hat, as well as a monocle. He is in charge of the house and is extremely strict about the house rules, but he is also seen to put the rules before common sense, as seen in "Destination: Imagination" when he sticks to the rule written on the chained up toy box of never letting the imaginary friend who is trapped in there out despite what would happen to him if he did not. He is often found punishing Bloo for his various misdemeanors. It was revealed in "Busted" that the reason Mr. Herriman is so hard on Bloo is because he feels that, given that he is allowed to stay at Foster's even though he still has an owner, he has already broken one of the main house rules. He is extremely fond of his creator Madame Foster, harboring great respect and loyalty to her, even at her most prominent levels of unabashed pep and energy. He has a fear of dogs (due to the fact that dogs are the natural predators of rabbits) and is easily scared out of his wits whenever he comes across one. He also has a rabbit's stereotypical obsession with carrots and will do anything to have them, as demonstrated in "Crime After Crime".
=== Madame Foster ===
Madame F. Foster (voiced by Candi Milo) is the founder of Foster's and grandmother of Frankie. She's an old person but has childlike boundless energy and enjoys herself to the fullest. Her imaginary friend is Mr. Herriman, whom she imagined when she was a child and never gave up, and is the only one who can control him. Like Bloo, Madame Foster occasionally becomes hyperactive and mischievous. However, there are times she is shown to be the wisdom of the house.
== Recurring characters ==
Duchess (voiced by Grey DeLisle) - A banshee-like high-maintenance pedigree imaginary friend who is pompous, ugly, rude, arrogant, selfish and lazy up to the points she orders Frankie to open her eyelids for her first thing in the morning. She considers herself superior to all the other imaginary friends, is extremely negative towards everyone, and never says anything nice. Whenever Duchess turns on the spot, her entire body pivots like a sheet of paper being flipped, revealing that she is two-dimensional. Her full name is "Her Royal Duchess Diamond Persnickety the First, Last, and Only". She speaks with a German accent. Details about Duchess's life before moving to Foster's or who created her remain a mystery since neither Duchess nor her creator were even shown at the reunion in "Good Wilt Hunting".
Mac's Mom (voiced by Grey DeLisle) - The mother of Terrence and Mac who is rarely shown but often mentioned. She tells her youngest son Mac to give up Bloo because she gave up her imaginary friend at his age. She seems completely unaware that Mac visits Bloo at Foster's everyday.
Goo (voiced by Grey DeLisle) – A hyperactive, happy-go-lucky, overly imaginative and talkative African-American girl who first appeared in "Go Goo Go". Her parents allowed her to name herself when she was a baby resulting in the full name "Goo Goo Ga Ga". Goo enjoys playing games such as Checkers and Truth or Dare, but she does not know how to play and Mac is the only one who notices. In her first appearance she constantly created imaginary friends because she had no real friends because of her weirdness. She finally stopped making new friends and undoes them after Mac told her to get to know the ones she had made already. However, she has still created a few by mistake or to help on rare occasions. She is also shown to be friends with Cheese, as both of them get along because of their odd doings. Despite appearing older than Mac, her exact age has never been stated.
Terrence (voiced by Tara Strong) – Mac's sadistic older brother and the recurring villain of the series. He enjoys bullying Mac and coming up with various schemes to make Mac's life hard and miserable. His stupidity always gets the better of him, making him easily outsmarted by Mac or Bloo.
Cheese (voiced by Candi Milo) – The simple, dimwitted, light yellow imaginary friend who debuted in "Mac Daddy". Cheese was thought to be an imaginary friend accidentally created by Mac, but was actually created by Mac's neighbor Louise. He appears to be a nuisance and dimwitted, often saying incoherent or non-sequitur phrases, and breaking into sudden bouts of screaming when frightened or when he does not get his way. Cheese likes goldfish crackers, cereal, juice, chocolate milk (although he is lactose-intolerant), etc.. He is prone to flatulence. In the series finale "Goodbye to Bloo", he becomes the newest resident at Foster's, much to the other residents' horror.
== Recurring imaginary friends ==
Fluffer Nutter (voiced by Grey DeLisle) – A small pink squirrel-like friend.
Bloppy Pants (voiced by Jeff Bennett) – A shy and nervous grey tabby cat-like friend.
Yogi Boo Boo (voiced by Tom Kenny) – A tall green giraffe-like friend who speaks with an Indian accent. His name is a parody of Yogi Bear and Boo-Boo Bear.
Billy the Squid (voiced by Tom Kenny) – A pink octopus/alien-like friend with 3 horn-like appendages on his head.
Sunset Junction (voiced by Keith Ferguson) – A tall navy blue bear-like friend with carpet-like fur wearing a woolen scarf.
Jackie Khones (voiced by Phil LaMarr) – A tiny green one-eyed stick figure-like friend. Despite his tiny size, He speaks in a deep voice.
Handy (voiced by Keith Ferguson) – A friend who appears as an animate baseball mitt.
Scissors (voiced by Tom Kenny) – A friend who resembles a pair of scissors with bird-like legs with the scissors forming a beak.
Uncle Pockets (voiced by Kevin Michael Richardson) – An old clown-like friend who resembles Willy Wonka, the Cat in the Hat or the Mad Hatter, considered widely to be the best imaginary friend ever.
== Other characters ==
World/Tyrant King (voiced by Max Burkholder) – An imaginary friend, and the main and later former antagonist of "Destination: Imagination".
Red (voiced by Phil LaMarr) – Terrence's imaginary friend and rival, who he creates in "Seeing Red". Red is a red-colored cube-like creature similar to Bloo with arms and a face but no legs and refers to himself in third person.
Ivan (voiced by Kevin McDonald) – A seeing-eye friend created by a blind kid named Stevie (a parody of Stevie Wonder and Steve Urkel) with over 100 eyes. He is first seen in "Sight for Sore Eyes".
Berry (voiced by Grey DeLisle) – A polite magenta friend. Has a crush on Bloo, but dislikes how close Mac and Bloo are. Berry is jealous and disrespectful of Mac despite the latter being Bloo's creator.
Bendy (voiced by Jeff Bennett) – A non-canon yellow Grinch-like friend with black stripes, and the main antagonist of the equally non-canon episode "Everyone Knows It's Bendy". Bendy was put up for adoption by his family when they could no longer tolerate his destruction around their house. Immediately after his arrival, he begins committing crimes, such as breaking a vase and leaving mud in the house, and framing the other imaginary friends, getting them punished for his wrongdoings until Bloo comes up with a master plan. Due to Bendy never actually getting any consequence for his actions even by the end of the episode, the other characters being constantly punished for his crimes, and Mr. Herriman and Frankie acting way out of character by siding with him, Bendy's appearance was so infamous that writer Lauren Faust apologized for writing the episode that he appeared in, and he was permanently written out of the show and the episode was declared non-canon as a result.
== References == | This is a list of characters from the Cartoon Network animated television series Foster's Home for Imaginary Friends.
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357 | mac | List of It's Always Sunny in Philadelphia characters (wikipedia) | The following is a list of recurring characters from the FX television series It's Always Sunny in Philadelphia.
== The Gang ==
=== Charlie Kelly ===
Charles "Charlie" Kelly is the janitor of Paddy's Pub and a co-owner, a childhood friend of Mac, and high school friend of Dennis. Frank is his roommate and until "The Gang's Still in Ireland", it was hinted that Frank might be the biological father of Charlie. Charlie is illiterate in the English language, even though he repeatedly denies this. Charlie is an alcoholic and a chronic user of inhalants. He suffers from various psychological problems including but not limited to anger management issues and possible borderline personality disorder. Charlie often screams to get his point across and refers to the dirty work of the bar as "Charlie Work". He is shown to be the most unintelligent member of the gang, making plans that almost always end up affecting the entire plotline in a negative way. He is played by Charlie Day.
=== Mac ===
Mac is Charlie's childhood friend and Dennis' high school friend and later roommate. He is a co-owner of Paddy's Pub and its bouncer. He brags about his incredible hand-to-hand combat skills, strength, and general athletic ability though it is quite obvious he lacks any real skill or even a proper sense of balance. He is shown to be constantly seeking approval from others.
His full name is revealed to be Ronald McDonald in the seventh-season episode "The High School Reunion", though his last name involving "Mac" had been established since the introduction of his father. It is heavily implied throughout the series that Mac is gay, even momentarily coming out of the closet in season 11, and again in season 12, although this time permanently. He also displays anti-semitic views, driven by his Catholic upbringing. He is played by Rob McElhenney.
=== Dennis Reynolds ===
Dennis Reynolds is Deandra's twin brother, main bartender, and co-owner of Paddy's Pub. He is narcissistic, superficial, demented, hypersexual, selfish, and abrasive, perpetuated by his Ivy League education at the University of Pennsylvania. Dennis is repeatedly implied to be a sociopath, and in one episode was diagnosed with borderline personality disorder and prescribed medication. His sense of self-worth is entirely dependent on what others think of his appearance and he often suggests the best way to sleep with a woman is to use his personal system, the D.E.N.N.I.S. system (a satire of seduction community techniques for bedding women).
He is revealed to be an atheist in the season 7 episode "Sweet Dee Gets Audited". He is also a big fan of the music of Rick Astley, Bryan Adams, and Steve Winwood. He uses the nickname "The Golden God" for himself, although no one else calls him by it. He is played by Glenn Howerton.
=== Deandra "Sweet Dee" Reynolds ===
Deandra Reynolds (usually called Dee or Sweet Dee) is Dennis's twin sister, the main waitress at Paddy's Pub, and the show's main female character. She is self-absorbed, shallow, petty, and the most often subject to ridicule from The Gang in many different forms: they call her extremely ugly (resembling a bird in a negative and humorous way), lazy, and completely talentless. They don't count her as one of the gang, but rather as just someone who works for them.
Dee dreams of becoming an actress even though she has no acting experience or acting talent. She aspires to be a comedian, although suffers from a crippling fear of doing stand-up, often dry-heaving before she can deliver the punchline. Like her brother, Dee is egotistical and often states that she thinks she is talented and pretty, although she is constantly told otherwise. She is played by Kaitlin Olson.
=== Frank Reynolds ===
Frank Reynolds is the legal (but not biological) father of twins Dennis and Dee, and until "The Gang's Still in Ireland", was hinted at being the biological father of his roommate Charlie. In season 13, his expired driver's license displays his date of birth as July 31, 1943. With an Irish-American surname and an Italian-American appearance (but apparently a member of neither community), his ethnicity is unclear. He constantly carries a gun with him and frequently pulls it out for any number of situations. He used to be a successful businessman with a long history of illegal operations (such as running sweat shops, drug-dealing, and working for Jeffrey Epstein "on the sex island" to score discounted snorkeling) and dealings with sordid characters.
Owning 51% percent of shares at Paddy's Pub, Frank "The Captain of the Gang" is considered to be the de facto boss and makes a majority of the business decisions at the bar. Though he is fairly wealthy and has the money to live elsewhere, he chooses to live in squalor with Charlie in order to add excitement to his life following his split from his ex-wife Barbara, to whom he frequently refers as his "whore wife". This lifestyle choice involves eating cat food, using a "toe knife", living on about five dollars a week (not counting his morning cocaine routine), keeping a mini meats fridge in his apartment, as well as sausages in his shirt pocket, and sharing a bed (which is also their couch) with Charlie.
He is the only member of the gang to frequently involve himself with politics, often ranting about how bad the government is. He doesn't believe in or trust psychiatrists, and was admitted into a school for clinically insane children for a short while as a child before he was cleared of any legal mental issues, having received a certificate stating that he did not have "donkey brains". He is frequently seen in strip clubs and sleeping with prostitutes (even proposing marriage to a "crack whore" in the season 7 premiere). He is played by Danny DeVito.
== Recurring characters ==
=== Artemis Dubois ===
Artemis Dubois (Artemis Pebdani) is one of the more frequently recurring secondary characters, introduced in "Charlie Gets Cancer" as Dee's friend from her acting classes who acts out a scene from Coyote Ugly (a film that featured Kaitlin Olson in a small part). Artemis is overly serious about her craft and displays bizarre habits and outbursts. She is very open about her sexuality and often offers to perform in the nude, even when it is unnecessary. Recently, she was involved in a sexual relationship with Frank and the two shared a food fetish. She likes having sex with bacon bits in her hair because it "makes her feel like a Cobb salad." She and Frank once had makeup sex in a dumpster behind Wendy's, where she incorporated a bun. She has openly proclaimed that she has a "bleached asshole". In the season 11 episode "Being Frank" it is shown that Artemis' family is Jewish.
=== Brad Fisher ===
Brad Fisher (Nick Wechsler) is first introduced as the Waitress' fiancé in the season 5 episode "The Waitress Is Getting Married". Brad dated both Dee and the Waitress in High School but both dumped him because of his acne. He rekindles both relationships in a plot to humiliate them. Charlie gives Brad a wedding gift of a box full of hornets. Brad returns in the season 7 episode "The High School Reunion" where his face is scarred from the hornet stings. He gets "revenge" on Charlie for this by attempting to give him a wedgie when Charlie has passed out from huffing chemicals in a restroom, but is horrified when Charlie's filthy underwear splinters into shreds in his hands.
=== Carmen ===
Carmen (Brittany Daniel) is a trans woman who was dating Mac. She first appears in the season 1 episode "Charlie Has Cancer", then reappears in the season 3 episode "Mac Is a Serial Killer". She is attractive and displays an obvious bulge in her pants. She keeps Mac interested in her with promises of undergoing gender affirming surgery and with constant flattery of Mac's physique. In "Mac Fights Gay Marriage", she has had genital reassignment surgery and has married Nick, much to Mac's dismay. In "Dee Gives Birth" it is revealed that Carmen is the father of Dee's baby (she had her sperm frozen before she had GRS) and that they used an anonymous egg donor and Dee was merely a surrogate. Dee gave the baby to Carmen and her husband Nick to raise. In the unaired pilot, Carmen is portrayed by Morena Baccarin.
=== Duncan & Z ===
Duncan (David Gueriera) and his right-hand man, Z (Chad Coleman), are Frank's bizarre friends that he met under a bridge. They appear in "Charlie Kelly: King Of The Rats" where Frank wants the gang to invite them to go to the gang's luau. They later appear in "Dee Gives Birth" to provide music for their party/interrogation of Dee's potential baby's daddies. Z also makes a brief appearance in "The Gang Tries Desperately to Win an Award," as The Gang attempts to show that they are a diverse crowd; the episode then makes a pointed reference to the no-Emmy wins-ever show Coleman formerly starred on, The Wire when Dennis flatly states that "black bars don't win awards." Z appeared in the season 12 premiere, "The Gang Turns Black."
=== Da Maniac ===
Da Maniac (Roddy Piper) is a deranged, homeless wrestler. The gang enlists him for their wrestling act in season five, and he drifts into both their timeshare scam and pyramid scheme in season 9, the latter of which he proves surprisingly adept at.
Da Maniac is legitimately disturbed, with Dennis noting that "his mania is NOT confined to the ring." He is seen reacting violently over a fifteen dollar debt, foraging chestnuts for food, and displaying extreme PTSD. When the guys suggest that he adopt a terrorist-themed persona for a match, his response is simply to repeat the phrase "I'm... da Maniac" until it is clear he will not respond to anything else. When asked if he has children, he ominously replies, "Naw... not anymore." He also claims to love the members of the gang, "even with [their] feathers," all while calling Mac the N-word behind his back.
Despite his mental illness, da Maniac is a competent wrestler, with props, determined rates, and a sense for wrestling trends. He also displays marked skills as a salesperson in "Mac and Dennis Buy a Timeshare", far outselling all other Invigaron distributors.
Piper died in 2015.
=== Ernie ===
Ernie (David Zdunich) is the "Barfly" who is commonly seen in the background in the bar. He is in every single episode that is shot in the bar, but he is noticed in the episode "Paddy's Pub: The Worst Bar in Philadelphia" handing over the paper to the "gang" for them to see the journalist's article. Also, in "Sweet Dee is Dating a Retarded Person" in which he sets up Mac, Frank and Charlie's band equipment. David Zdunich died in 2009. A portrait of Ernie (Zdunich) is hung behind the bar in memoriam.
=== Gladys ===
Gladys (Mae Laborde) is a senior citizen the gang calls upon who has a penchant for long rambling stories. She played the piano during Charlie's play in the season 4 finale "The Nightman Cometh". Dennis pretends she is his grandmother to win back a former girlfriend in "The D.E.N.N.I.S. System". She claims she was friends with Calvin Coolidge and that her grandmother was the lesbian lover of Susan B. Anthony. Laborde died in 2012.
=== Josh Groban ===
Josh Groban (played by himself) is a famous singer. Dee and Artemis are huge Groban fans, calling themselves "Grobanites". Dee's love of the singer leads her to self-tan and wear white shorts, explaining "Josh Groban likes his ladies to pop". Dee and Artemis get backstage passes to a Groban show, but Dee is unable to attend because Frank had poisoned her and tied her up. In the season 9 episode "The Gang Saves the Day," Groban appears in a fantasy of Dee's. In the fantasy, Dee is a celebrity who achieves fame after entering witness protection through her portrayal of an English butler character, in an allusion to the 1980s television series Mr. Belvedere. She marries Groban, but their marriage lasts only 17 minutes with Dee divorcing Groban for Brad Pitt.
=== Jack Kelly ===
Uncle Jack Kelly (Andrew Friedman) is Charlie's uncle (the brother of Charlie's mother Bonnie) and a lawyer. He first appeared in the season 1 finale "Charlie Got Molested" wherein Charlie's family gives him an intervention to get him to admit he had been molested by his elementary school teacher (this belief was fostered by the scam the McPoyles were running to extort money from the school system). Uncle Jack appears again in the season 5 episode "The Great Recession." When Charlie tries to move back in with his mother after Frank kicks him out of their apartment, she reveals that she sublet Charlie's room to Uncle Jack to earn extra money. Jack insists they share the room and spend time wrestling there. In the season 6 episode "Dennis Gets Divorced," Charlie and Frank call in Jack, who is revealed to be a lawyer, to handle their divorce. Later, Dennis and Mac use him to try to get their apartment back from Dennis' ex-wife, only to find that she hired The Lawyer. Jack proves to be incompetent, getting the apartment back in exchange for Dennis taking his wife's $90,000 debt. Jack has a bizarre fixation on the size of his hands, constantly worrying that they may appear to be too small. It is heavily implied that Uncle Jack is a pedophile and wants to have sex with his nephew. Charlie has mentioned how, as a child, he would stay awake at night because Uncle Jack would want to sleep in his bed. Coincidentally, Charlie's lyrics to "Nightman" seem to revolve around a man sneaking into his room at night and raping him. In season 13's "Time's Up For The Gang" Charlie denies he was molested by Uncle Jack.
=== The Lawyer ===
The Lawyer (Brian Unger) is a recurring character first seen in "Dennis and Dee's Mom Is Dead" where The Gang mistake him for having personal involvement as the executor of Barbara Reynolds' will. He returns in season 5, eager to personally stop Frank—he represents a family that Frank is trying to force out of their house. After Charlie makes an attempt to prove that he's more legally apt than the actual lawyer, he challenges him to a duel; the lawyer immediately accepts, claiming to have a loaded gun in his office desk. He also appears again in "Paddy’s Pub: Home of the Original Kitten Mittens" when The Gang goes to him to get patents for products that they have created. He later tricks them into signing a document that grants him all the profits from the products as well as imposing a restraining order on them. He is also present at the end of "Dennis Gets Divorced" where he works pro-bono for Maureen Ponderosa, securing a deal with Charlie's Uncle Jack Kelly, who is a lawyer, where Dennis can keep his apartment in exchange for assuming $90,000 of Maureen's debt. In season 11, he represents one of the McPoyles in a lawsuit against Bill Ponderosa over a bird attack that cost his client an eye, but in addition to being hit with nonsensical anti-Semitic baiting from Frank and Dee (even though he's not Jewish), he ends up injuring one of his eyes in another bird attack that leads to Bill's acquittal.
=== Lil Kev ===
Kevin Gallagher (Kyle Davis) a popular local rapper who is possibly mentally disabled. He is introduced as Dee's boyfriend in "Sweet Dee Is Dating A Retarded Person," where the gang makes ableist assumptions toward him. Dennis convinces Dee to dump Kevin because he's challenged, only for her to later decide he isn't. He later returns as one of Dee's baby's potential fathers in "Dee Gives Birth".
=== Korean Busboy ===
The Korean Busboy (Maxie J. Santillan Jr.) worked at the Korean restaurant that threatened to steal business away from Paddy Pub's in "The Gang Solves The North Korea Situation". Dee sleeps with him to get information about their secret microbrew recipe. He gives her a note written in Korean purportedly containing the recipe, but when the Gang has it translated it turns out to read "Bony American is dirty dirty whore. She bring much shame to herself and country." He later returns as one of Dee's potential baby's fathers in "Dee Gives Birth". Santillan died in 2022.
=== Rickety Cricket ===
Matthew Mara, better known as Rickety Cricket, or simply Cricket, (David Hornsby), is a former Catholic priest who becomes defrocked, destitute, abducted, assaulted (both physically and sexually), threatened, hunted, severely injured, and addicted to PCP all directly or indirectly resulting from the influence or actions of the Gang. As a boy he suffered from a medical condition that required the use of very conspicuous complex leg braces which inspired the pejorative nickname "Rickety Cricket". He first appears in "The Gang Exploits a Miracle" where it is revealed that he has continued to harbor a high school crush on Dee (who at the time used an elaborate semi-permanent aluminum medical back brace). He admits he was convinced to eat horse feces for a chance to kiss Dee, which she refused since, as she says, "his breath smelled like shit". Mac and Dennis have been teabagging Cricket at every opportunity since high school. Dennis claims that he has a shoebox full of pictures of him and Mac doing this, and pictures are surfacing on the Internet.
One recurring theme in the series is Cricket's downward spiral; due to his involvement with the Gang he leaves the priesthood, supports himself by grifting or panhandling, becomes addicted to PCP and crack cocaine, has his legs broken by members of the Philadelphia Mafia, frequently commits sex acts with dogs, has his throat sliced by Frank in a wrestling match, is hunted by Mac and Dennis for sport, and suffers a gunshot wound in his hand when he is trespassing at Paddy's and Frank accidentally shoots him. He is then left bleeding in the car by Frank and Dee while they go into a store full of hurricane-panicking people, and he ends up driving through the doors of the place and further injuring himself. The wound to his throat wasn't fatal, but got badly infected, severely damaging his vocal chords and giving him a gravely voice. He has since carried a vendetta against The Gang and attempts to get his revenge in various episodes, but consistently fails to do so. He shows up in "Mac's Big Break", when he appears on Dennis and Dee's inaugural podcast, remarking about his life as a homeless person - during this episode he reveals that he stopped believing in God since "a Chinaman stole my kidney". He also shows up in "Dee Gives Birth" because Frank was trying "to cast a wider net" in finding out the identity of Dee's baby's father and he considered Rickety Cricket to be "the wildcard". He shows up at his high school reunion cleaned up, claiming to have returned to being a priest. However, he actually uses the opportunity to steal jewelry from the other alumni. The other alumni mock him and physically eject him when it is discovered he has ringworm, but his rants about how Dee loved and left him leads the cool crowd to reject her. In the season 8 premiere, "Pop–Pop: The Final Solution", he is working at a local pound for community service. He has a new scar over his now-blind left eye, which he says was from a "skirmish" with a stray chocolate lab, in which he paralyzed the dog; later on he makes numerous references to raping and being raped by feral dogs. He claims to be a dog executioner, but then admits he's a janitor.
In season 9, he suffers horrific facial burns when he's locked in Mac and Dennis's apartment during "The Gang Squashes Their Beefs" when a fire breaks out (ironically, he was not even invited because the Gang didn't consider him someone they'd wronged), leaving the entire left side of his head covered in scar tissue. In season 10, when Charlie and Mac seek him out to help make their old friend Psycho Pete crazy and fun again, he is fully homeless and describes in disgusting detail the sex acts he must perform to earn money for alcohol and other drugs (frequently remarking that it will cost a six pack of beer for him to perform oral sex). Also from season 10 onwards, his crack-addicted life on the streets has resulted in him losing many of his teeth. By seasons 10 and 11, he often casually appears in the bar to use its bathroom to smoke PCP in, and/or to perform sex acts for money. After having half of his head nearly burned off, he also stops giving any thought whatsoever to his physical appearance, with long, filthy, matted hair and scraggly beard. While he occasionally gives himself wipe-down showers in the bar's bathroom, he is almost always covered in an extensive coating of dirt and grime. In the season 11 episode "Dee Made a Smut Film", Cricket says that a cat bit off one of his toes at some point, and describes in exacting detail how he was involved in a dog orgy (almost bragging about it).
Cricket is given his own storyline in the season 12 episode "A Cricket's Tale". In the episode, his father finds him and gives him a chance to turn his life around and work at his company. Cricket accepts the job offer and starts turning his life around and meets a woman he falls in love with. However, it turns out that Cricket was hallucinating from PCP and that the woman is actually a dog. Dejected, Cricket decides to turn back to his old lifestyle. In the episode, the gang casually mentions that they injected a GPS pet tracking chip into Cricket's body, without his knowledge.
=== Dr. Larry Meyers ===
Dr. Larry Meyers (René Auberjonois) is the high-school drama teacher who taught Dee. He appeared in "The Gang Gets A New Member", in which Dee and the Gang open a time capsule and find a check from Dee to him for a million dollars. Dee goes back to her high school to talk to Dr. Meyers. He tells her that he was an alcoholic and that she must give up. He also reminds her of a musical she was in, Frankenstein. Later he trips and gets injured as a result of Charlie becoming a member of the school's custodial staff and waxing Dr. Meyers's classroom. He does not appear again in the series due to the injury. Dee takes over as a substitute. Auberjonois died in 2019.
=== Principal Brian McIntyre ===
Principal Brian McIntyre (Dave Foley) is the high school principal who hires Dee as a substitute teacher and Charlie as a janitor in "The Gang Gets A New Member". He fires both of them in the next episode "Dee Reynolds: Shaping America's Youth" because Dee took her students on a field trip to Paddy's Pub to watch Mac and Dennis's Lethal Weapon 5 movie and because Charlie's mentoring of a student named Richie led to him dressing up in blackface after watching the movie. The principal laments that he probably won't be employed at the school much longer, due to their shenanigans. Principal McIntyre appears again in the episode "Gun Fever Too: Still Hot", where he is now the principal of a middle school. It is revealed that because of tenure, he was reassigned instead of being terminated.
=== The McPoyles ===
Fraternal twin brothers Liam (Jimmi Simpson) and Ryan McPoyle (Nate Mooney) are creepy, incestuous, former elementary-school classmates of Mac and Charlie. They are introduced in "Charlie Got Molested" in Season 1 when they falsely accuse a former teacher of pedophilia. Charlie and the gang foil their plan and turn them in to the police, which sparks the McPoyles' antipathy toward the Paddy's Pub gang. Their clan is built entirely from inbreeding and Liam and Ryan have an incestuous relationship with each other and their deaf-mute sister Margaret (Thesy Surface). As seen in "The Gang Gets Invincible" in Season 3, they have at least 14 other siblings and family members, who all sport the McPoyle unibrows, acne, and eczema. The most notable relative is Doyle McPoyle (Bob Rusch), an aspiring football player who lost his chance to play for the Philadelphia Eagles when a hallucinating Frank accidentally shot him in the leg.
Ryan, Liam, and Margaret avenge this in the episode "The Gang Gets Held Hostage" by faking a raid on the bar. Ryan seems to have an addiction to inhaling Pledge furniture cleaner, and all the McPoyles seem to exclusively drink milk and to prefer warm, clammy conditions, which explains their constant sweaty appearance. In Season 8, Liam becomes engaged to Maureen Ponderosa in the episode "The Maureen Ponderosa Wedding Massacre", which would break the incestuous bloodline if successful, but the marriage is called off after Dennis sleeps with Maureen. During the wedding Liam loses his right eye in a riot triggered by Bill Ponderosa spiking the McPoyles' milk with bath salts. Ryan and Liam later reappear in the Season 9 episode "The Gang Squashes Their Beefs" as part of an ensemble invited to Dennis and Mac's apartment to make amends for past transgressions. Liam and Ryan are revealed to be the owners of the very last video rental store in Philadelphia whom accept the Dennis and Mac's invitation to Thanksgiving dinner. During the episode Liam displays immense difficulty adapting to his disability, relying on Ryan for assistance in most situations, as well as wearing a flesh-colored eye-patch and later painting on an eye in the hopes of making his injury less visible. As retribution for Liam's disfigurement the brothers demand a new eye from Dennis and Mac, to no avail. As the episode ends Frank manages to set fire to Dennis and Mac's apartment. The McPoyles along with the other guests are locked inside the burning apartment by the gang but seemingly escape unharmed. The McPoyle family return in the Season 11 episode "McPoyle vs. Ponderosa: The Trial of the Century", pursuing legal action against Bill Ponderosa for spiking the milk at the wedding and the subsequent mutilation of Liam. Though many members of the family are present at the trial (including Margaret McPoyle) Liam and Ryan do not attend, as it transpires Liam contracted pink eye after pouring "healing milk" into his eye. The case is thrown out of court due to a revelation made by Charlie that the true culprit responsible for Liam's injury was Royal McPoyle, the pet Poconos Swallow of Pappy McPoyle (Guillermo del Toro), patriarch of the McPoyle family.
Liam and Ryan make an appearance in the Season 16 episode "The Gang Goes Bowling" where they are revealed to have sold their video store and now own and manage the bowling alley that the gang bowls at during a battle of sexes match between Charlie, Dennis, Mac and Frank against Dee, the Waitress, Artemis and Gail the Snail.
=== Ingrid "Fatty Magoo" Nelson ===
Ingrid Nelson AKA Fatty Magoo (Judy Greer) was a high school friend of Dee's who appeared in the season 3 episode "The Aluminum Monster Vs. Fatty Magoo". In High School Dee wore a back brace and was dubbed the Aluminum Monster while Ingrid was morbidly obese and was given the name Fatty Magoo. Dee would always build herself up and put Ingrid down. Ingrid grew up to be a rich and successful fashion designer. Dee, feeling threatened by Ingrid's success, tried to get the Gang's help in destroying Ingrid while Dennis tried to sell his dress design to her, even going so far as to wear it himself. Ingrid later returns in the season 7 finale "The High School Reunion: The Gang Gets Revenge" where the Gang's efforts to pick on her fail badly: Dee's deranged insults of her just make Ingrid roll her eyes and walk away (and even sociopathic Dennis thinks Dee looked like an idiot there, something Dee silently agrees with) and when Mac and Charlie taunt her for being "fat" she insults them in turn and abruptly cuts off a short conversation, leaving them standing around looking like losers.
=== Gail the Snail ===
Gail (Mary Lynn Rajskub) is Dennis and Dee's disgusting cousin (the daughter of their mother Barbara's sister Donna). Dennis and Dee found the best way to get rid of her is to throw salt at her, hence the nickname. She first appears in Season 5 when Frank goes to her father's funeral and attempts to pick up her mother Donna. Gail gives Frank (her uncle by marriage) a handjob under the table in front of her mother. In Season 9, Dee later invites Gail, who is now working at a local Wawa convenience store, to a Thanksgiving dinner at Dennis and Mac's apartment to "squash their beefs". Gail is one of the many people the Gang leaves in a fire in Mac and Dennis's apartment at the Thanksgiving dinner. In Season 13, Gail is seen on the same flight as Dee, Artermis, the Waitress, Mrs. Mac, and Bonnie Kelly who are trying to do a lady reboot of a previous episode where the gang tried to outdo Wade Boggs' record of beers drunk on an airplane flight. In Season 16, Gail appears as part of a bowling team alongside Dee, Artemis and the Waitress in a battle of the sexes bowling match between Dennis, Charlie, Mac and Frank.
=== Nick ===
Nick (Windell Middlebrooks) is Carmen's portly African-American husband. Mac is initially annoyed that Carmen had moved on to Nick instead of calling him after she had her penis removed. Mac does not agree with gay marriage and quotes the Bible verse Romans 1:27 to Nick, to which Nick responds with the Bible quote Exodus 21:20 endorsing slavery. Nick later appears in "Dee Gives Birth" where it is revealed that Dee is a surrogate for the couple since Nick cannot have kids but Carmen had frozen her sperm before her operation. Middlebrooks died in 2015.
=== Bill Ponderosa ===
Bill Ponderosa (Lance Barber) first appears in "Mac Fights Gay Marriage" and the follow-up episode "Dennis Gets Divorced" as Dee's high school crush and the brother of Dennis's high school girlfriend, Maureen Ponderosa. He has put on a lot of weight since high school and become a lecherous drug addict who neglects his family. Dee eventually becomes his mistress when Dee thinks he bought her a new car when in fact the car belongs to another of Bill's mistresses. Bill returns to his wife. Bill later returns in "Dee Gives Birth" as one of Dee's baby's potential fathers. Bill reveals that he tells girls he's had a vasectomy so he doesn't have to use a condom. He appears in the episode "The Maureen Ponderosa Wedding Massacre", where he spikes a punch bowl with bath salts and it is revealed that Frank is his AA sponsor. He also displays an affinity for cocaine. Ponderosa also appears in the season 11 episode "Being Frank", where it is revealed that he and Frank have developed a friendship based on hard partying and other social activities and that Frank has nicknamed him "Pondy." Frank borrows Ponderosa's car to help the rest of the gang spring Dennis' Land Rover from a city impound lot without paying, dropping Ponderosa off at a roller rink, where he ends up being brutally beaten by a group of men for hitting on underage girls. Ponderosa also makes a brief appearance in the season 12 episode "Making Dennis Reynolds a Murderer", where he implies in an interview that he does not miss his dead sister and that Dennis "did us all a favor. You ever seen a grown woman take a dump in a sandbox?" He states that Dennis did not kill Maureen, who "died three years ago". He killed Bastet, a reference to Maureen having come to identify as a cat and begun transitioning, having renamed herself after the Egyptian cat goddess.
=== Maureen Ponderosa ===
Maureen Ponderosa (Catherine Reitman) is Dennis's high school girlfriend and the sister of Bill Ponderosa. Dennis eventually gets back in touch with Maureen and marries her in "Mac Fights Gay Marriage". She has a dead tooth that makes her breath "smell like she nibbled on little pieces of shit". Dennis gets tired of Maureen fairly quickly and in "Dennis Gets Divorced" she hires the Lawyer as her divorce attorney, ending up in a total demolition of Dennis where he has to assume her tens of thousands of dollars in debt as well as pay her monthly alimony. She later appears in "The High School Reunion" and reveals she's spending her alimony money on a diamond for her dead tooth. Maureen eventually got her dead tooth removed, as well as getting a breast enhancement sometime between seasons 7 and 8. She became engaged to Liam McPoyle but on the day of the wedding, upon seeing Maureen's new body, Dennis sleeps with her again. By season 10, she has undergone a series of bizarre plastic surgeries in order to turn herself into a literal "cat lady", and, in season 11, she says in a courtroom that she wants to be referred to as just a "cat", period. She dies in the season 12 episode "Making Dennis Reynolds a Murderer", and Dennis is the prime suspect (considering the aftermath of their divorce), until it's revealed neither he nor anyone else murdered her; she was trying to walk along the edge of a roof like a cat and fell off it, landing in an alley headfirst where she broke her neck and died. Despite these revelations, Charlie and Mac try to paint Dennis as the killer via a Making a Murderer-style documentary. However, a comment Dennis makes in the season 14 episode "Paddy's Has a Jumper" about her being pushed implies that he did indeed kill her. In the season 16 episode "The Gang Gets Cursed", Dennis also slips up and claims Maureen was murdered, and when Dee accuses him of having done it himself he does not explicitly correct her.
=== Rex ===
Rex (T. J. Hoban) first appears in "America's Next Top Paddy's Billboard Model Contest" as one of the male models vying for the spot on Paddy's Pub's billboard. Although an early favorite of Frank's, eventually Frank himself appears on the billboard. He also appeared in the season 6 episode, "Dee Gives Birth" as a potential father of Dee's baby although it is later revealed that Dee was acting as a surrogate for Carmen and her husband Nick. Rex also appears briefly in the season 9 episode "The Gang Saves the Day" as an angel in part of Mac's fantasy. Rex also made an appearance in the finale of season 10, "Ass Kickers United: Mac and Charlie Join a Cult." Rex also appears in the two-part S13 episodes "Charlie's Home Alone" and "The Gang Wins the Big Game."
=== Peter "Schmitty" Schmidt ===
Peter Schmidt aka Schmitty (Jason Sudeikis) is a former member of the gang back in high school. Mac and Dennis kicked Schmitty out of the gang (and a moving car) to make Charlie happy. Charlie and Schmitty used to be roommates and Charlie always feels upstaged by Schmitty. The gang kicks Charlie out and welcomes Schmitty back in the season 6 episode "The Gang Gets A New Member", but he quickly earns their ire when he upstages Mac and Dennis and is kicked out again. He returns in the season 7 finale "The High School Reunion: The Gang Gets Revenge" and appears right at the end of the reunion, seemingly now forgiving the gang, to take the Waitress up on her drunken offer to bang 'the next guy who talks to her', right before Charlie can utter a word.
=== Ben the Soldier ===
Ben Smith a.k.a. Ben the Soldier (Travis Schuldt) is first introduced in "The Gang Wrestles for the Troops" as Dee's online chat buddy "soldier of fortune". Dim-witted and genial, he served as an American soldier in Iraq. He is mistaken as a disabled person while getting off a bus from the airport in a wheelchair. Dee reluctantly says he was talking to Artemis over the internet, due to him being disabled but soon discovers he isn't; he just twisted his knee getting off a plane in Germany. Ben is seen again in the episode "The D.E.N.N.I.S system" as Dee's boyfriend. He dumps her, calling her a "mean person" and goes for a pharmacist that dumped Dennis after the latter "Dennis-ed" her. Ben resurfaces again in season six with the episode "Mac's Big Break." Ben is seen chiefly wearing the jean shorts Frank purchased for him as a welcome-home gift. He appears again in "Dee Gives Birth" as a potential father of Dee's child. He is again seen wearing the jean shorts, and breaks down in tears when discussing Dee's manipulative behavior towards him. He next appears in ”Mac & Dennis buy a Timeshare” when the Gang attempts to get themselves out of their financial schemes by triggering his PTSD. It is revealed Ben doesn't suffer from PTSD, he was a computer programmer who never saw actual combat. In "Charlie’s Home Alone" and "The Gang wins the Big Game" he is among the characters that go with the Gang to Super Bowl LII.
=== The Unknown Actor ===
The Unknown Actor (Geoffrey Owens) first appears in the episode "The Gang Gets Invincible" when the gang tries out for the Philadelphia Eagles. He pretends to be Donovan McNabb doing a plug for McDonald's but the gang calls him out, recognizing him as "that guy from The Cosby Show" who played "Sondra's husband Alvin." Owens was indeed on The Cosby Show as Sondra's husband Elvin. In the season 7 episode "Frank's Pretty Woman", he appears, claiming to be Tiger Woods paying Frank's hooker girlfriend for her services, revealing that he's into "foot shit." Dee calls him out for not being Tiger Woods and recognizes him as that actor who pretended to be Donovan McNabb. He then claims to be actor Don Cheadle, but Dee doesn't fall for it, either. It's implied that Dee does take him up on his offer to pay her to play with her "bizarrely huge" feet. He also appears in S10 E4, Lethal Weapon 7, as an actor playing Murtaugh.
=== The Waitress ===
The Waitress (Mary Elizabeth Ellis) is the most frequently recurring character outside of The Gang. Introduced in the first episode, "The Gang Gets Racist," as the object of Charlie's affections, she works at a coffee shop near Paddy's. She has absolutely no interest in Charlie but does have sex with him in season 12 "Dennis' Double Life" and has also slept with Frank and Dennis. She harbors an unrequited crush on Dennis, who slept with her in the episode "Charlie Has Cancer". Attempting to make Dennis jealous, she "banged" Frank in "Mac Bangs Dennis' Mom" and grinds on a homeless man in "The Gang Dances Their Asses Off". She nearly has relations with Mac in "Mac's Banging the Waitress".
She spent a night with Charlie at the Jersey Shore while she was high on ecstasy; in the morning she was sickened and left, but Charlie was just happy he got to spend that time with her. Charlie goes to great lengths to woo her, while she goes to great lengths to attract Dennis' attention. Frequently, her infatuation with Dennis causes her to make decisions against her better moral judgment and often end up the victim of The Gang's manipulative schemes. She is a recovering alcoholic, a fact first referenced in "The Gang Gives Back," when she becomes Charlie's Alcoholics Anonymous sponsor, and then in "Who Pooped the Bed", "The Waitress Gets Married", and "The Gang Beats Boggs: Ladies' Reboot."
As a running gag, her real name is never mentioned; she is simply referred to as "The Waitress," and directly as "Waitress." It was hinted Charlie may know her name in "The Gang Sells Out" when he chides her for liking Dennis when he doesn't even know her real name. The only clues to her name are that it does not start with "W" and is not "Beautiful," the name Dennis guessed when he was accused of not knowing it. In "The Waitress Is Getting Married," it is revealed that she went to high school with the Gang, where she and Dee dated the same guy (a retcon after not knowing Dee when they 'first meet' in the second episode of the series). She attends the high-school reunion with the Gang, where her name tag is missing (further implying her status as 'easily forgettable', a theme in that episode), preventing her name from being revealed. Many fans assumed her name was Nikki Potnick when Frank showed up with a stolen tag bearing that name. However, Glenn Howerton specified on Twitter that this is not the case. Nikki Potnick is mentioned by Charlie in the episode "Underage Drinking: A National Concern" when he reminisces how the gang crashed Potnick's car into a tree during a night of underage drinking. In a tongue-in-cheek online special feature for season 10, Ellis is filmed making a promotional video and about to reveal her name when Glenn Howerton arrives. Howerton begins to allude to bad things happening to her and when she does not understand, he reveals her real-life husband Charlie Day pointing a sniper rifle at her. She whispers in his ear what she believes to be her name, but Howerton says it is wrong and calls off Charlie. After the men leave, she tried to report the crime but screams when she is asked for her name and does not know it.
== Parents ==
=== Barbara Reynolds ===
Barbara Landgraf Reynolds (Anne Archer) was Frank's gold-digging ex-wife and Dennis and Dee's mother whom Frank always refers to as "my whore wife" who appeared in Season 2. She was a cold, cruel and selfish woman who had no love or affection for her entire family. She is the daughter of Heinrich "Pop-Pop" Landgraf, an SS officer who escaped to America via the ratlines. Barbara tricked Frank into raising the twins, Dennis and Dee, because she thought he was wealthier than their biological father, Bruce Mathis. When she meets Bruce again, she is startled to learn he is actually a wealthy philanthropist. She died off-camera of a botched neck lift operation in the third season. An ecstatic Frank delivers the news of her death to The Gang while smoking a cigar and popping a champagne bottle. Frank later tricks the gang into exhuming her body to teach them a lesson (having convinced them that she had faked her own death and buried her jewelry in her grave), leaving Dee and Dennis horrified.
=== Bruce Mathis ===
Bruce Mathis (Stephen Collins) is Dennis and Dee's biological father. The antithesis of Frank, Bruce devotes his time and money to charities and philanthropic efforts, including adopting several suffering children in Africa. He reconnects with his twins through Dee's MySpace page, but they are unable to have a successful relationship with him because of his good nature clashing with their selfish ways. Bruce had always been wealthy but never mentioned it to Barbara who assumed he was poor and was thus surprised to learn about his wealth years later. After Barbara's death, he inherits Barbara's fortune (including her house, which originally went to Dennis until Mathis films evidence of Frank's presence in the house, which was against the terms of Barbara's will) and calls The Gang "the most horrible people alive."
=== Bonnie Kelly ===
Bonnie Kelly (Lynne Marie Stewart) is Charlie's mom. She is a sweet and timid woman who is attracted to cruel men. She had a one-night stand with Frank Reynolds 30 years ago. She later reconnects with Frank, enjoying his harsh treatment becoming his "bang maid," but she quickly transfers her affections to Mac's intimidating father Luther after meeting him at a dinner party thrown by Mac and Charlie. Quite neurotic and emotional (possibly suffering from obsessive compulsive disorder), she is prone to dramatic episodes. There is evidence that Bonnie may have once been a prostitute, which is later revealed to be true, a fact which greatly upsets Charlie. In "Mac's Mom Burns Her House Down", Mac's mother accidentally burns her house down and moves in with Bonnie. At first they can't stand each other, but they eventually bond over their mutual racism and xenophobia.
=== Shelley Kelly ===
Shelley Kelly (Colm Meaney) is Charlie's biological father. He was pen-pals with Charlie since he was a child. Charlie assumed he was just a friend, while the gang does not believe he existed, as they would converse in a made-up language. However, it is revealed in “The Gang's Still in Ireland” that Shelley was actually his father and that they were conversing in Gaelic. Charlie agrees to follow his father's footsteps, willing to become a cheese monger and to live in Ireland. However, Shelley dies of COVID-19 after it is revealed that Frank is not vaccinated. The gang throws him off a cliff, a Kelly family tradition.
=== Luther Mac ===
Luther McDonald (also referred to as Luther Mac) (Gregory Scott Cummins) is Mac's father and a convicted felon. He is tall, has numerous tattoos, and never blinks resulting in a very intimidating appearance. Out of fear, he is one of the few people The Gang does not immediately try to manipulate or exploit. The warm and gentle Bonnie Kelly is attracted to Luther's aloof behavior and criminal past. In his first appearance ("Dennis and Dee Get a New Dad"), he attempts to get Mac and Charlie (who have come to visit him in prison to bond with him) to smuggle heroin into the prison in their rectums. In "Dennis Looks Like a Registered Sex Offender", he is out on parole and convinces Mac to help him "take care of some people" he has listed, including former witnesses in his trial and the judge who sentenced him. Charlie and Mac become convinced that he is using them as drivers while making the rounds to murder the people on his list (similar to the movie Collateral) and try to get Luther sent back to prison. They fail to do so and Mac is initially relieved when Luther is arrested for violating the parole on his own. However, Mac is horrified to learn that Luther was apologizing to the people on his list and didn't harm any of them, and his parole violation occurred when Luther made proscribed plane reservations to leave the state and take Mac and Charlie to the Baseball Hall of Fame. Luther calmly tells Mac he had no plans to hurt him before, but once he gets out of prison again, he's definitely going to murder him and Charlie. When he is paroled anew, Mac and Charlie fake their deaths to escape what they believe is his unstoppable wrath. Luther forgives Mac for this in a note where he tells his son that he loves him and always had and to stay away from him for the rest of their lives. In "Mac Kills His Dad", Luther is the suspect in the beheading of a state official. Mac learns that the murder was committed by Luther's presumed lover Eduardo Sanchez and reveals this to Bill Ponderosa, who goes to the police intending to confess the crime himself but decides at the last minute to rat on Eduardo. This leads to the other inmates in the jail to think Luther is the rat and it is implied that Luther is attacked by the other inmates as a result. When Mac finally comes out of the closet to Luther in the Season 13 finale when Mac does an elaborate ballet performance for the jail inmates, Luther is visibly angry and walks out of the room without any words.
=== Mrs. Mac ===
Mrs. McDonald (also referred to as Mrs. Mac) (Sandy Martin) is Mac's mom. She is always portrayed smoking and usually watching television, completely apathetic to what's going on around her, and openly states that she hates both Mac and Luther, and the entire human race in general. When Mac and Charlie fake their deaths, she falls asleep at her son's "funeral" with a portable TV on her lap. Due to her damaged vocal cords as a result of her chain smoking, she often communicates through unenthused grunts which Mac translates. In Season 6, she accidentally burns her house down and moves in with Bonnie Kelly, the two bonding over their mutual racism. Mac claims that she is a skilled mechanic, having worked all the way up to the position of manager at a Jiffy Lube, which, despite Charlie's skepticism, she demonstrates by repairing Bonnie's ceiling fan. She rarely speaks, but often makes comments that are racist and xenophobic when she does.
=== Heinrich "Pop Pop" Landgraf ===
Heinrich "Pop Pop" Landgraf (Tom Bower) is Dennis and Dee's anti-Semitic maternal grandfather (and presumably their cousin Gail's) who is languishing in a nursing home and is rarely visited by relatives. A former SS officer who escaped punishment for his crimes, Pop Pop remains an unrepentant Nazi. In his youth, he was the spitting image of Dennis, much to the disturbance of Mac and Charlie. Charlie accidentally leads him to believe he is Dennis when he and Dee visited him in "The Gang Finds a Dead Guy". Charlie finds a box with Pop Pop's old Nazi uniform and a painting by Hitler. In season eight, a home video from the early 1980s shows that as children, Dennis and Dee were forced to attend a neo-Nazi Hitler Youth camp coordinated by their grandfather. In "Pop–Pop: The Final Solution", The Lawyer informs Dennis and Dee that they are the next of kin and must decide whether they want to pull the plug on Pop Pop. After the two of them could not come to a decision they turn power of attorney to The Lawyer. He tells the doctor to pull the plug, but Pop Pop begins to breathe on his own.
Bower died in 2024.
== References == | The following is a list of recurring characters from the FX television series It's Always Sunny in Philadelphia.
| 1 |
358 | mac | List of Veronica Mars characters (wikipedia) | Veronica Mars is an American television series created by Rob Thomas. The series premiered on September 22, 2004, during network UPN's last two years, and ended on May 22, 2007, after a season on UPN's successor network, The CW. Balancing murder mystery, high-school, and college drama, the series features social commentary with sarcasm and off-beat humor in a style often compared to film noir. Set in the fictional town of Neptune, the series stars Kristen Bell as the title character, a student who progresses from high school to college during the series while moonlighting as a private investigator under the wing of her detective father.
The first season had seven regular characters. However, Thomas decided to introduce and eliminate several characters in order to create an "equally fascinating mystery" for the series' second season. Thomas needed "new blood" since he felt unable to bring back the Kanes and the Echolls and "have them all involved in a new mystery". The third season features a cast of ten actors who receive billing, an increase from the nine actors in the second. Three of the regulars in the second season are written out of the series, two new characters are introduced and two others are upgraded from recurring roles.
== Overview ==
== Main characters ==
=== Veronica Mars ===
Kristen Bell portrays the titular Veronica Mars, a high school junior and skilled private detective. More than 500 women auditioned for the role; Bell felt that it was "just luck" that Rob Thomas saw that "I have some sass to me, and that's exactly what he wanted." Bell thought that her "cheerleader looks and outsider's attitude" set her apart from the other women who auditioned.
=== Duncan Kane ===
Teddy Dunn portrayed Duncan Kane, Veronica's ex-boyfriend and Lilly's brother. Dunn originally auditioned for Logan but ended up portraying Duncan Kane. Dunn left the series midway through the second season because Thomas felt that the Logan-Veronica-Duncan love triangle had run its course. He needed to put "other guys in her life" to keep the series fresh and attributed Dunn's removal to fan interest in the Logan-Veronica relationship, saying "It became clear that one suitor won out".
=== Logan Echolls ===
Jason Dohring played Logan Echolls, the "bad-boy 09er" son of an A-list actor. Dohring originally auditioned for the role of Duncan Kane. After his audition, the producers asked Dohring to audition for Logan's character, who was only going to be a guest role in the pilot. Dohring felt that his audition for Duncan "was a little dark", and was told by the producers that it was "not really right". The producers then asked Dohring to read for the role of Logan. Dohring acted out one scene from the pilot, bashing a car's headlights in with a tire iron. During the final auditions, Dohring read two times with Bell and met with the studio and the network. When reading with Bell, Dohring acted the whole scene as if he was the one who raped her and tried to give the character a certain evil feel.
=== Wallace Fennel ===
Percy Daggs III portrayed Wallace Fennel, Veronica's best friend and frequent partner in mystery solving. Daggs auditioned for Wallace's role twice before being cast and had to go through three tests with the studio and network executives. During his first audition, Daggs read four scenes from the pilot. Just before his studio test, Daggs read with Bell and had "a great conversation." He said that she "made me feel comfortable about auditioning" and was a big reason why he became more comfortable playing Wallace as the season went on.
=== Eli "Weevil" Navarro ===
Francis Capra portrayed Eli "Weevil" Navarro, the leader of the PCH Biker gang and Veronica's ally. Despite often being in trouble with the law, Weevil helps Veronica solve many of her cases. He is wrongfully accused of fellow gang member Thumper's murder and is arrested at his graduation. He later becomes a janitor at Hearst College after he is cleared.
Capra reprises his role in the Veronica Mars film, in which Weevil is revealed to have since married a woman named Jade, with whom he has a daughter, Valentina.
=== Keith Mars ===
Enrico Colantoni played Veronica's father Keith Mars, a private investigator and former Balboa County Sheriff. Keith's targeting of billionaire Jake Kane as the primary suspect for Lilly Kane's death led to a public outcry for Keith Mars to be immediately removed from office. Disgraced, Keith was forced into private investigator work. Veronica often helps him solve cases.
=== Mallory Dent ===
Sydney Tamiia Poitier played Mallory Dent, Veronica's journalism teacher at Neptune High, through the first half of the first season. Ms. Dent, as she was commonly referred to, was the only teacher who took Veronica at face value, not based on prejudices. Together with Veronica, she was responsible for uncovering the voting scam that led to Duncan winning the school elections illegally. Ms. Dent left her job after becoming pregnant. Although she was given regular series billing, Poitier appeared in only four episodes but was given credit for seven. Poitier's removal from the series was rumored to be due to budget issues.
=== Jackie Cook ===
Tessa Thompson portrayed Jackie Cook in the second season as Wallace's romantic interest and the daughter of a famous baseball player. Fan reactions to the character were generally negative, particularly after Veronica witnessed Jackie talking to a guy while dating Wallace. Thomas blamed the character's reception on his error in judgment: he had hoped fans would question whether it was Jackie or Veronica in the wrong; however, the audience automatically assumed that it was Jackie. Thomas decided not to change the story arc he had planned for Jackie, as he believed Thompson was "a fantastic actress and she's got more to play." He said that whether fans ended up liking Jackie was "up in the air", but he hoped that they did because "she's really, really good". Jackie was subsequently written out of the series at the end of the second season.
=== Dick Casablancas ===
Ryan Hansen portrayed Richard "Dick" Casablancas Jr., an 09er friend of Logan, a womanizer and former high-school bully turned frat boy. Dick was a recurring character in the first season but was upgraded to series regular in the second season.
=== Beaver Casablancas ===
Kyle Gallner acted as Cassidy "Beaver" Casablancas, Dick's introverted younger brother. Cassidy was a recurring character in the first season, but was upgraded to series regular in the second season.
=== Cindy "Mac" Mackenzie ===
Tina Majorino portrayed Cindy "Mac" Mackenzie, a computer expert befriended by Veronica. While looking into Mac's parents' past as a favor for her, Veronica uncovers that Mac was accidentally switched at birth with Madison Sinclair by the hospital where they were both born, but the respective parents did not learn about this until years later, by which time they had already grown to love their accidentally adopted daughters. Mac was a recurring character in the first two seasons but was upgraded to series regular in the third.
=== Parker Lee ===
Julie Gonzalo portrayed Parker Lee, Mac's extroverted roommate at Hearst College, described by Thomas as "everything that Mac is not." Parker was introduced in the third season as a series regular.
=== Piz ===
Chris Lowell played Stosh "Piz" Piznarski, Wallace's roommate at Hearst College and a music lover with his campus radio show. Piz was introduced in the third season as a series regular and was named after the director of the pilot, Mark Piznarski. The character's role was to have another male friend for Veronica, middle-class and not upper-class. Thomas used the radio show as a narrative device to capture the mood of the university. Throughout the third season, Piz is implied to have a crush on Veronica. The two develop a friendship, although he's initially hurt by seeing her with Logan. After Veronica breaks up with Logan, she starts dating Piz in "Debasement Tapes." When a sex tape of Veronica and Piz starts circulating via email, Logan beats up Piz, believing him to be behind it. Veronica's investigations revealed that the video originated from a Hearst College secret society named The Castle.
Piz reappears in the Veronica Mars film, where he is shown to have since relocated to New York City with Veronica. When she temporarily visits her hometown to help her ex-boyfriend Logan find a lawyer, she gets dragged to her high-school reunion by Wallace and Mac. Piz shows up at the reunion to surprise her, only to join the fight that ensued after Madison Sinclair played a copy of his and Veronica's college sex tape. Piz returned to New York the following morning. After she stayed in Neptune longer than initially planned and didn't show up to meet Piz's parents, he later broke up with Veronica.
=== Don Lamb ===
Michael Muhney portrayed Don Lamb, the Balboa County Sheriff who won the office from Keith in the recall election spearheaded by Jake Kane. Lamb was a recurring character in the first two seasons, but was upgraded to series regular in the third.
=== Gia Goodman ===
Krysten Ritter portrays Gia Goodman, a student at Neptune High and the daughter of influential professional baseball team owner Woody Goodman. Gia transfers to Neptune High from a private boarding school. She attends the class field trip to Shark Field and meets Dick Casablancas, his brother Cassidy, Duncan Kane, and Veronica for the first time. Gia rides the school bus on the way to the stadium. However, she opts to ride in Dick's limo with the other "09ers" on the way back. The bus crashes and all of the passengers die, save for Meg Manning. Later in the year, Gia invites Veronica to her slumber party. Veronica attends; however, she has an ulterior motive and is investigating families that Meg babysat for. When Gia is sent footage of herself at her brother's soccer game, she hires Veronica to find the sender. Gia and Veronica's friendship is broken when a feud erupts between their fathers, and she fires Veronica from the case. When Veronica realizes that Gia's stalker is Neptune High's janitor, Tommy "Lucky" Dohanic, she rushes to her aid. Lucky is arrested, but he is released when the Mannings pay for his bail. The next day, he comes to school with a gun looking for Gia; however, he is shot and killed by school security.
Gia reappears in the Veronica Mars film as a wealthy socialite engaged to Luke Haldeman, a former classmate. Veronica initially suspects her to be responsible for Carrie Bishop's death (who became a self-destructive pop star under the name Bonnie DeVille before the film's events). Veronica connects the murder to Carrie's best friend, Susan Knight, who allegedly died in a boating accident nine years earlier. She concludes that Gia and Luke, who were on the boat with Susan, covered up her death and killed Carrie because she threatened to confess. Veronica sends bugged flowers to Gia's apartment and calls her, playing recordings of Carrie's voice in an attempt to scare her into confessing. Gia panics and calls Stu "Cobb" Cobbler, another classmate who was on the boat with her. Veronica goes over to her apartment to confront her, and Gia reveals Cobb was the mastermind behind Carrie's death as well as what happened on Susan's boat; Susan succumbed to Alcohol poisoning, and Cobb took photos of a panicked Carrie, Gia, and Luke dumping Susan's body. He's been using the images to blackmail everyone. Veronica's bug broadcast everything on a frequency she believed to be unused but was used by a local rock station. Cobb heard everything from a radio in his apartment in the building across the street and then shot Gia through the window before coming after Veronica. Veronica calls the police and lures Cobb to the basement, beating him unconscious with a golf club. Gia is revealed to have died from her gunshot wound after Cobb is arrested and guilty of murdering her and Carrie.
=== Alonzo Lozano ===
Clifton Collins Jr. portrays Alonzo Lozano, a hitman for a Mexican cartel. Introduced in season 4, he begins a romantic relationship with Weevil's sister Claudia.
=== Daniel Maloof ===
Mido Hamada portrays Daniel Maloof, a congressman and Alex's older brother. After Tawny's family attempts to attack him and Alex over an engagement ring, he hires Logan as his bodyguard.
=== Matty Ross ===
Izabela Vidovic portrays Matty Ross, a teenager who lost her dad in bombings.
== Recurring characters ==
=== Members of main characters' families ===
==== Casablancas family ====
===== Kendall Casablancas =====
Charisma Carpenter portrays Kendall Casablancas (Kendall Lacey Shifflet, a fake real name; really Priscilla Banks), Cassidy and Dick's gold-digging stepmother. Kendall first appears in the Season 2 premiere, having married real estate magnate Richard Casablancas, seemingly for his vast wealth. She becomes the stepmother of Dick and Cassidy and begins an affair with their friend, Logan. Cassidy hires Veronica to investigate his stepmother, and she discovers that she helped Richard commit real estate fraud. Veronica told Cassidy and gave the information to the Securities and Exchange Commission; however, Richard fled the country before he could be arrested. Richard's lawyers told Kendall that while the boys both had trust funds, essentially, she had nothing. Kendall became desperate for money, and began selling Richard's belongings, and turned to Logan and Duncan, but no avail. Cassidy, who had started a real estate company called Phoenix Land Trust, needed Kendall to be his CEO for business purposes because of his underage status. Although Kendall and Cassidy admitted their mutual dislike of each other, the salary prospect eventually made Kendall come around. The business continued, though most people assumed Richard was behind Phoenix Land Trust, not Cassidy. When Cassidy informs Kendall they need to acquire more capital, she goes and visits the incarcerated Aaron. She makes a deal with him: he will buy into Phoenix Land Trust if she goes to Duncan and Logan's suite and gets something for him. Kendall goes to the suite and removes some of Duncan's hair from the shower drain. Aaron later uses the hair to plant false evidence implying Duncan committed the crime he was on trial, and Aaron was acquitted.
When Keith discovered that Kendall is the beneficiary of the life insurance policies on her stepsons, who could have been killed in the bus crash that claimed the lives of several people, he began investigating. He and Veronica discover that everything they know about Kendall is a lie; she is not a dumb trophy wife, rather a con artist named Priscilla Banks. She had been working with the Fitzpatrick crime family, and spent time in jail to protect her lover, Cormac Fitzpatrick (Jason Beghe). Keith breaks into Kendall's home, which leads to a dangerous confrontation with Kendall and Liam Fitzpatrick. When Cormac is released from prison, Keith reunites the two, trying to escape from Liam Fitzpatrick with the money Kendall received from Phoenix Land Trust. As Keith leaves the two, Cormac shoots and kills Kendall and tries to attack Keith, who escapes. Keith believes he got Kendall killed and feels guilty since he and Kendall had formed a cordial relationship while he was working for her. He goes back to the crime scene with the police, but neither Kendall nor Cormac's body are found, who is believed to have been killed by Liam for not giving up the money.
==== Richard "Big Dick" Casablancas ====
David Starzyk portrays Richard "Big Dick" Casablancas Sr., Cassidy and Dick's father. Richard marries Kendall to be a trophy wife and openly favors Dick over Cassidy. When Veronica discovers that he has committed real estate fraud and tells the U.S. Securities and Exchange Commission (SEC), Richard flees the country before he can be arrested.
Richard reappears as a recurring character in season 4. It's revealed he did a stint in prison after the SEC finally caught him.
==== Terrence Cook ====
Jeffrey Sams portrays Terrence Cook, an ex-major-league baseball player, gambler, and Jackie's formerly estranged father. He's introduced in season 2 along with Jackie. Terrence is initially suspected of causing a bus crash that killed several Neptune High students in the season 2 premiere.
==== Echolls family ====
===== Aaron Echolls =====
Harry Hamlin plays Aaron Echolls, an Oscar-winning A-list actor and is the main antagonist during the season 1 finale. At the beginning of the series, Aaron is married to his second wife, Lynn, with a son Logan. He adopted his daughter Trina while married to his previous wife. Aaron has numerous female fans due to his impressive physique and good looks. While Aaron is beloved by the American public, in real life, he is very different. Aaron cheats on his wife, and easily angered, he physically abuses Logan, but tolerates Trina. Aaron quits acting when Lynn commits suicide and tries to reconcile with Logan and Trina. Upon learning that Trina's boyfriend is physically abusing her, he beats the boy, threatening more if the boy ever returned. When Veronica exposes him as the man who killed Lilly, Aaron is indicted and held without bail. Logan visits his father in a holding cell after new evidence implicates Logan in a murder case. Aaron claims that he is innocent and tries to convince his son that he had been wrongfully accused. Logan, who despises his father, does not believe Aaron's story but recognizes that the evidence against Aaron is circumstantial at best. Later, Kendall visits Aaron in prison, and he agrees to invest in Phoenix Land Trust if she gets some of Duncan's hair. Aaron uses the hair to plant false evidence implying Duncan committed the crime, and Aaron is acquitted. He goes to the Neptune Grand and has sex with Kendall. While she is in the shower, Clarence Wiedman appears and kills Aaron with a silenced pistol on Duncan's orders.
===== Lynn Echolls =====
Lisa Rinna portrays Lynn Echolls, Logan's mother and Trina's stepmother. Lynn was a famous movie star who was married to Aaron Echolls, an even bigger movie star. Lynn tried to ignore Aaron's abuse of Logan by turning to alcohol and pills. After Aaron received several threatening letters, Lynn turned to Keith to discover who was behind them. It turned out to be a caterer who had seen Aaron having an affair at a party, and he had her fired. At the Echolls's Christmas party, the caterer knifed Aaron in the gut. Aaron recovered and hired Keith to find out who was leaking stories of his many infidelities to the press, only to discover Lynn. When Aaron confronted Lynn, she said that she wanted to hurt him as he hurt her, went back to her car, took some pills, and drove away. Her car was found abandoned on the Coronado Bridge. She had jumped, but no body was found. Even after the funeral, Logan refused to believe that his mother was dead. He thought she left him clues that she was still alive (e.g.: leaving behind a lighter engraved with "Free At Last" that she always kept in her purse) and that she was faking her death to get away from Aaron. Logan hired Veronica to prove his mother was alive; however, a video filmed by a freshman and his friends who were making a movie showed jumping from the bridge in the background, the exact time it was believed Lynn had jumped. Logan finally realizes that she's gone due to the video's evidence and after discovering that Trina was the one using his mother's credit cards. With all hope gone of his mother being alive, he breaks down crying in Veronica's arms. Later, when Lynn's will was read, it was discovered she had recently altered it, cutting Aaron out and leaving everything to Logan. Trina initially thought she had been cut out, too, only to be informed that she had not been left anything before it was altered.
===== Trina Echolls =====
Alyson Hannigan plays Trina Echolls, Logan's adopted sister and a struggling actress. She is first mentioned by Aaron in "Clash of the Tritons," who says that she is the only one who will talk to him. Logan asks Veronica to investigate his mother's death, and they discover Trina is staying at the Neptune Grand. The film Trina had been shooting in Australia had not worked out, and she had decided to return home. Trina moves back into the house and gets into trouble with money after borrowing money from her boyfriend, Dylan. She asks Logan for a loan; however, he does not give her any money. Because Trina can't pay Dylan, he beats her to which Logan finds out about after seeing her limp and has a black eye. Once Dylan arrives to talk to Aaron about starring in his movie, Aaron confronts him and beats him.
In "My Mother, the Fiend," Trina returns to Neptune as the "Special Celebrity Director" of the school play. During this time, Veronica investigates the case of a baby left in the bathroom of Neptune High during the prom of 1980. She believes Celeste Kane is the mother and wants her to own up to abandoning the child. Veronica eventually discovers Trina was the prom baby and tells Trina the truth, excited at the thought of inheriting some of Celeste's wealth. The next day at school, Veronica and Trina talk when Mary, the deaf lunch lady, begins pointing to herself and then to Trina. Veronica eventually deciphers her sign language: Mary is Trina's biological mother. It turns out then-student Mary had an affair with a teacher, and she left baby Trina at his doorstep. He then left the baby in the bathroom at the prom, knowing they would think it belonged to a student. It turned out the teacher was the current principal, Alan Moorehead. Trina busts him in the middle of a staff meeting in front of all the other teachers, and he is fired.
As a result of Hannigan's busy schedule, several of her storylines had to be swapped between episodes. Thomas said that he "loved having Alyson in the show" and had "a lot of fun with her".
==== Alicia Fennel ====
Erica Gimpel portrays Alicia Fennel, Wallace's mother, dated Keith Mars at the end of season one and season two. Alicia later breaks up with Keith after he tried to investigate her past with Wallace's biological father.
==== Kane family ====
===== Jake Kane =====
Kyle Secor recurs as Jake Kane, Lilly and Duncan's father, a software billionaire. He is Lianne Mars' sweetheart in high school and was having an affair with her at the start of season one. Jake invented streaming video, making him one of the most influential men in Neptune, California via his software company, Kane Software. When Veronica interviews Abel Koontz, he suggests that Veronica is Jake's biological daughter rather than Keith's because Jake and Lianne once dated while in high school. Keith later has a paternity test and is proved to be Veronica's biological father. Jake returns in the series finale as a member of the secret society "The Castle."
===== Celeste Kane =====
Lisa Thornhill plays Celeste Kane, Lilly and Duncan's mother. Celeste loathed Veronica because of her husband's affair with Veronica's mother. She disapproved of Veronica and Duncan's relationship and told Duncan that Veronica could have been his half-sister because of Jake's affair with Lianne. This caused Duncan to break up with Veronica. Before Lilly died, Celeste had shown resentment towards her daughters' way of life and blamed every problem her family faced on Lilly. In "Donut Run", her last appearance, she hired Vinnie Van Lowe to find Duncan.
===== Lilly Kane =====
Amanda Seyfried portrays Lilly Kane, Duncan's older sister, Veronica's best friend, and Logan's girlfriend. Lilly was the daughter of Jake and Celeste Kane. She was murdered on October 3, 2003 – roughly eleven months before the show's first episode. Abel Koontz, a disgruntled employee, fired from Jake's firm, confessed to the crime and was awaiting execution. Lilly is seen on the show throughout a series of flashbacks and Veronica's daydreams, which portray her as a fun, wild, and stylish teenage girl. She was best friend to Veronica, who was dating Lilly's brother, Duncan. Before her death, Lilly had been dating Logan but had also been in a relationship with Eli "Weevil" Navarro, as Lilly did not like to be tied down. Lilly's murder changes Veronica's life completely, being the catalyst for a series of events that include Veronica's father Keith losing his job, Veronica's mother Lianne leaving town, and all of Veronica's friends abandoning her. Through the first season, Veronica investigates Lilly's murder and finds that nothing is what it seems. All three of the Kanes falsified their alibis, and Lilly's time of death was three hours off. Clarence Wiedman, the head of security for Kane Software, called in the tip that caused Abel Koontz to be arrested.
In the episode "Leave It to Beaver" Veronica and Duncan discover several videotapes in Lilly's bedroom. They show Lilly in bed with Aaron, Logan's father. Veronica realizes that Aaron killed Lilly to get the tapes back. When Duncan found her body, he went into a catatonic state. When his parents discovered him reeling over Lilly's dead body, they assumed he had killed Lilly in an epileptic seizure. To protect their son, they began an elaborate cover-up of the murder. However, before Veronica can take the tapes to the police, Aaron tries to kill her. After a chase, Keith arrives, and he manages to subdue Aaron, and he is arrested. Later that night, Veronica has a dream about Lilly. The two of them are floating in a lily-covered pool. Leaning back and smiling, Veronica declared this was the way things were supposed to be and how they would be from now on. Lilly smiles sadly and replies, "You know how things are going to be from now on, don't you? You have to know." She then asks Veronica not to forget about her, and Veronica turns to see that Lilly has disappeared and she is alone in the pool. Veronica promises that she could never forget her best friend. Lilly also appears as a hallucination in the season two premiere, "Normal Is the Watchword". Distracted by seeing Lilly, Veronica misses the bus and has to ride with Weevil back to town instead; the bus later crashes, and all aboard eventually die. Lilly returns for one last dream sequence in "Not Pictured", wherein Veronica's subconscious suggests that Lilly would have attended Vassar had she lived. As high-spirited as ever, Lilly brags about her sexual experiments and promises Veronica will understand once she goes to college. A painting of Lilly is seen in the season 3 finale as an homage to the character.
Thomas described Seyfried as "the biggest surprise of the year." When casting Lilly Kane, who would only appear occasionally as "the dead girl," Thomas did not receive the same level of actors who auditioned for the role of a series regular. Thomas said that he had "never had a more cut and dry audition" than he did with Seyfried. He said that she was "about 100 times better than anyone else that we saw; she was just spectacular". He said that she ended up being so good in the series that he used her three or four more times than he initially planned.
==== Lianne Mars ====
Corinne Bohrer recurs as Lianne Mars, Veronica's estranged and alcoholic mother. Lianne was the high school sweetheart of Jake Kane, who she believed was Veronica's father. At Neptune High, Lianne Reynolds was credited to being a gossip and a friend to the deaf girl, Mary, who was later revealed to be the biological mother of Trina Echolls. Lianne later marries Keith; however, she has an affair with Jake. After the Lilly Kane murder is made public, Lianne develops a drinking problem and leaves town. When she returns, claiming to want to fix her problems, Veronica spends all of her college savings to enter her mother into rehab. Lianne returns to stay, seemingly sober; however, Veronica finds out that Lianne did not finish rehab. Veronica asks Lianne to leave, who steals the $50,000 settlement Veronica received from the Kanes on her way out. Lianne reappeared in Veronica's dream, where Lilly was never murdered, and Lianne is the perfect mother.
==== Charlie Stone ====
Ryan Eggold guest stars as Charlie Stone, Logan's half-brother and Aaron's son. When Logan asks Veronica to investigate his rapidly declining trust fund, she uncovers that Logan's father, movie star Aaron, had an illegitimate child. To keep this fact a secret from the tabloids, Aaron arranged for his accountant to deposit $10,000 a month from the Echolls estate into a fake charity set up to funnel the money to his son. After learning this information, Logan reaches out to his half-brother, finding a confidante and potential friend. Veronica continues her investigation to discover that the person Logan believes to be his half-brother (Matt Czuchry) is a writer for Vanity Fair who posed as Charlie Stone to get Logan to share personal details about growing up in the Echolls home. The real Charlie Stone refused to answer the reporter's questions, preferring to remain anonymous. Logan, believing that Charlie set up the reporter, reveals his brother's identity on Larry King Live in an attempt to scoop the magazine profile. After Veronica informs him that the real Charlie had nothing to do with the reporter, Logan tearfully contacts his half-brother again.
==== Nathan Woods ====
Cress Williams appears as Nathan Woods, Wallace's biological father with a shady past as an undercover cop.
==== Claudia Navarro ====
Onahoua Rodriguez recurs as Claudia Navarro, Weevil's sister, who begins a relationship with Alonzo.
==== Maloof family ====
===== Amalia Maloof =====
Jacqueline Antaramian portrays Amalia Maloof, Daniel and Alex's mother. She disapproved of Alex's engagement to Tawny Carr, going as far as offering to pay her off. She later hires Vinnie Van Lowe to find the ring Alex proposed with, which was a family heirloom.
===== Alex Maloof =====
Paul Karmiryan portrays Alex Maloof, Daniel's younger brother. Introduced in season 4, Alex was a victim of one of the bombings who survived. His parents disapproved of his fiancée Tawny Carr, who died in one of the bombings.
=== Residents of Neptune ===
==== Steve Batando ====
Richard Grieco portrays Steve Batando, a struggling actor and drug addict, as well as Mindy O'Dell's ex-husband. He killed Lamb with a bat then was shot and killed by Sacks.
==== Harmony Chase ====
Laura San Giacomo recurs as Harmony Chase, a married woman with whom Keith becomes romantically involved.
==== Leo D'Amato ====
Max Greenfield recurs as Leo D'Amato, introduced as the new Sheriff's Deputy, Veronica befriends. Without his consent, Veronica steals a recording of an anonymous tip implicating Abel Koontz in Lilly Kane's death from the evidence room. Leo is shortly suspended for the break-in, and when Veronica attempts to apologize, he is reluctant to forgive her. When Veronica admits she has fallen for him, he dismisses the claim; however, they kiss during her school dance. When Veronica secretly begins to date Logan, she confesses the affair to Leo and ends the relationship. The pair manage to remain on good terms, and Leo assists Veronica in breaking up a dognapping ring the same night she breaks up with him. To get enough money to send his little sister with Down syndrome to a private school, Leo steals and sells the Aaron Echolls and Lilly Kane sex tapes to Logan. Logan promptly destroys the recordings due to their traumatic nature; however, he inadvertently compromises the pending case against Aaron. Keith discovers Leo's participation in the theft; however, he covers for him by stating that the tapes were stolen because Leo was not at his post. Leo is promptly fired from the sheriff's department, but is able to keep the money that Logan paid him to help his sister. Leo begins working for a private security company and finds himself working for Woody Goodman's daughter Gia. Leo contacts Keith when he is concerned that his security company's warehouse is about to be robbed. Leo loses his job for involving Keith, although Keith asks him to return as a deputy. Greenfield reprises his role in the fourth season, where it is revealed that he has since joined the FBI and returns to Neptune to aid in the Spring Break bombing case.
==== Liam Fitzpatrick ====
Rodney Rowland plays Liam Fitzpatrick, a formidable Irish-Catholic gangster and drug dealer. Liam is in charge of the Fitzpatrick mafia family, also known as the Fighting Fitzpatricks. He shoots his brother, Cormac, in cold blood after Cormac fails to retrieve an original Van Gogh painting. It has been hinted that he and his family are helping Vinnie Van Lowe win the election for Sheriff. Liam tells Keith that if Vinnie does not win the election, or if Keith does anything to hurt Vinnie's campaign, he will kill Veronica.
==== Woody Goodman ====
Steve Guttenberg portrays Woody Goodman, the Sharks baseball team owner and Balboa County Executive. More commonly known as the "Mayor of Neptune," although the position is actually "County Supervisor." At the end of season two, he is revealed to be a pedophile who molested several boys on his Little League teams, including Cassidy Casablancas. Woody was killed when explosives planted by Cassidy blew up his private plane.
==== Tom Griffith ====
Rick Peters plays Tom Griffith, a plastic surgeon and coke-addict who the Fitzpatricks asked to testify that Logan killed Felix. Logan retaliated by dating his daughter Hannah until he dropped his charges.
==== Abel Koontz ====
Christian Clemenson plays Abel Koontz, Lilly Kane's falsely confessed murderer. Koontz was the person at Kane software who perfected streaming media but was cheated out of the patent. He then tried to invent a technology that "would put Kane out of business," though he failed, and his wife walked out on him. Three months after Lilly's murder, Koontz confessed to murdering her. Lamb found Lilly's backpack and shoes while searching Abel's houseboat, backing up Koontz's confession. Until this point, Keith's investigation was squarely focused on the Kane family as suspects. It was Keith's failure to investigate Koontz that led to his eventual ousting as Neptune's sheriff. A year later, when Veronica started to investigate Lilly's murder, she visited Koontz on death row twice. During their first visit, Koontz quickly recognizes Veronica and reveals that Jake Kane may be her birth father. She was suspicious of Koontz's confession because he fired his attorney while on death row, and she discovered that the same shoes found in Koontz's houseboat were in Lilly's room at the time of the murder. Veronica sneaked into Koontz's doctor's office and stole both his and Duncan's medical files. She found out that Duncan had type-4 epilepsy, whose symptoms included violent outbursts and seizures. For the first time, Veronica realized that Duncan was a possible suspect in Lilly's murder. She also found out that Abel Koontz had stomach cancer and that he was dying. She concluded that Jake Kane paid Koontz to confess to the murder, even though he was not the perpetrator, so that Keith Mars' investigation into the Kane family would end. Koontz accepted the offer because he knew he was dying and intended to give the money to his daughter, Amelia DeLongpré, who he had neglected in the past. Veronica locates Abel's daughter to help prove that he is innocent, but Clarence Wiedman, head of Kane security, bribes her with three million dollars in exchange for her silence. During Veronica's second visit to Koontz, she told him that she knew that he was dying and that he was paid to confess to the murder. Koontz's innocence was further solidified when Keith went to Las Vegas to talk to a prostitute with Koontz at Lilly's murder. Koontz's final appearance was in the second-season episode "Rat Saw God". After being cleared of all murder charges and released from prison, he asks Veronica to help locate Amelia before he dies. While investigating, Veronica discovers that Amelia's boyfriend killed her after they blackmailed Clarence Wiedman for more money. Instead of telling him the truth, Veronica says that his daughter was happily living in Aspen and that she could not fly down yet because of the weather. He then dies at the end of the episode, but it is not shown.
==== Cliff McCormack ====
Daran Norris recurs as Cliff McCormack, a Public Defender and Mars family friend. Cliff is a public defender in Neptune who has served as an ally to Keith and Veronica Mars and a steady client of Mars Investigations. Although rarely a key player in the series, he has had some notable and memorable appearances. In "The Rapes of Graff," Cliff was seduced by an escort hired by Aaron Echolls to steal Cliff's briefcase, which contained the Logan Echolls murder case files and keys to the storage locker containing Aaron's personal belongings, including an Oscar statue. Norris reprises his role in the fourth season, where he assists Mars Investigations in the Spring Break bombing case.
==== Mindy O'Dell ====
Jaime Ray Newman appears as Mindy O'Dell, Dean O'Dell's wife. Mindy and Cyrus share no children of their own, but parent Cyrus' adolescent son from a previous marriage and Mindy's younger son by her first husband, Steven Batando. In "President Evil," the O'Dells hire Keith to find Steven in the hopes that his bone marrow would be a match to that of his biological son, who has been diagnosed with leukemia. Keith locates Steven, who refuses to donate his marrow. When Batando later disappears, Keith suspects that the O'Dells kidnapped him and took the marrow donation against his will but looked the other way. In "Hi, Infidelity," Veronica finds Mindy sharing a hotel room with Hank, her criminology professor at Hearst College, and an employee of Cyrus'. Keith puts Mindy under surveillance after Cyrus hired him to find out if she's having an affair. Keith discovers no cheating, but Veronica reveals Landry's infidelity to her father, Keith, who tells it to Cyrus. Cyrus confides in Keith, saying that Mindy was too young and too beautiful, and their marriage had been doomed to fail. Mindy is preparing to leave Landry in the Neptune Grand hotel room they shared when Cyrus enters and confronts them both about the affair, brandishing a loaded pistol. When Cyrus is found shot to death in his office, the insurance company rules his death a suicide, leaving the O'Dell family with no compensation for the loss of income, in "Spit & Eggs." Mindy returns to Keith Mars and hires him to prove that Cyrus was murdered in "Show Me the Monkey." Mindy finally gets the insurance money from her husband's murder, buys a boat, and leaves town after being questioned by Acting Sheriff Keith Mars. Hank Landry catches up with Mindy on her boat, and he later confesses to accidentally killing her the night before being found, in "Papa's Cabin."
==== Vinnie Van Lowe ====
Ken Marino recurs as Vincent "Vinnie" Van Lowe, Keith's rival private investigator. Vinnie is a private investigator in Neptune and is the main competition for Keith and Veronica. Vinnie has rather lax moral standards and is often willing to take on cases that the Mars Investigation team would refuse. It is because of this that he has a much larger caseload than the Mars family. The cases that Vinnie Van Lowe takes on have sometimes helped the Mars family, but sometimes his work has been in opposition to Mars Investigations' cases. In "Kanes and Abel's," Veronica is attempting to find out who has been harassing Sabrina Fuller, the School Board President's daughter and one of the top candidates for the Kane Scholarship. The Kane Scholarship is a full scholarship named Lilly's honor, awarded to the valedictorian of Neptune High. In her investigation, Veronica discovers that one of the cars that was used during a harassment was owned by Vinnie Van Lowe's ex-wife, Debra Villareal. From this, she figured out that Vinnie Van Lowe was the person hired to harass Sabrina. In "Donut Run," Van Lowe was hired by Celeste Kane to watch Veronica because Celeste suspected that Veronica knew where Duncan took the kidnapped baby. Veronica was able to take advantage of Vinnie's willingness to change clients if he is offered a better deal. Veronica had Duncan offer Vinnie more money to drive the Manning baby and a Veronica look-alike over the Mexican border and pick Duncan up in Mexico. It was because of this that Duncan was able to escape authorities with the kidnapped baby successfully. In "Not Pictured," Vinnie and Keith team up to catch Woody Goodman. Vinnie had broken into the Goodman house and stole all their records. Vinnie was arrested but got away with the records. Using his one phone call, he meets with Keith to get him to split the bounty. Vinnie gives the records, and Keith gets the man. In "Welcome Wagon," he almost gets Keith killed while working for Liam Fitzpatrick. However, in "Of Vice and Men," Vinnie rescued Veronica and Meryl from danger from the Fitzpatricks when the two girls wander into the River Stix searching for Meryl's missing boyfriend. Marino reprises his role in the fourth season, where he is assigned by Congressman Daniel Maloof's mother Amalia to recover a family heirloom.
==== Clarence Weidman ====
Christopher B. Duncan recurs as Clarence Wiedman, the Head of Security at Kane Software. He kills Aaron Echolls at the end of season two on Duncan's orders. As Head of Security for Kane Software, Wiedman is known to do the less-than-savory jobs that Jake Kane needs to be done. It is known that Jake Kane called Wiedman before he reported his daughter's murder. Veronica speculates that he assisted in the cover-up of Lilly's actual time of death by lowering her body's temperature. It is known that Wiedman paid Amelia de Longpre so that her father, Abel Koontz, would falsely confess to the murder of Lilly. When Veronica found Amelia and tried to convince her to reveal the existence of the payoff money, Wiedman got to her first and gave her even more money so that she would leave Neptune, in "Kanes and Abel's." Wiedman also called in the anonymous tip that got Abel Koontz arrested and took photos of Veronica that were sent to Lianne Mars in "You Think You Know Somebody." Unfortunately, Amelia DeLongpre didn't stay away long. When Abel tried to get Veronica to find his daughter, Veronica found out that she had called Kane Software from a payphone across the street and confronted Wiedman about it. Later on, when Veronica found her body, Clarence was there and confessed that Amelia had asked for more money. As it turned out, it was Amelia's new boyfriend, Carlos Mercado, who had wanted the money, and after he got it, he killed Amelia. Wiedman traced the money to Las Vegas, and it was implied that he killed Carlos in "Rat Saw God." Wiedman made another appearance when Aaron was acquitted. In "Not Pictured" Aaron's hotel room, Clarence assassinated him with two bullets. Afterward, he called Duncan in Australia, who asked, "CW?" Wiedman responded, "It's a done deal." Duncan reprises his role in the fourth season episode "Entering a World of Pain" as Logan's replacement security detail for Congressman Daniel Maloof.
==== Penn Epner ====
Patton Oswalt recurs as Penn Epner, a delivery guy for Cho's Pizza and true crime enthusiast who also teams with Mars Investigations to solve the Spring Break bombing case.
==== Nicole Malloy ====
Kirby Howell-Baptiste recurs as Nicole Malloy, a friend of Veronica and owner of a Neptune nightclub.
==== Clyde Pickett ====
J. K. Simmons recurs as Clyde Pickett, an ex-con working as a fixer for Richard Casablancas and a friend of Keith.
==== Marcia Langdon ====
Dawnn Lewis recurs as Marcia Langdon, Neptune's chief of police.
=== Neptune High ===
==== Alan Moorehead ====
John Bennett Perry plays Alan Moorehead, the principal of Neptune High. When Moorehead was a teacher, he had an affair with then-student Mary, and she left their baby Trina Echolls at his doorstep. He then left the baby in the bathroom at the prom, knowing they would think it belonged to a student. Many years later, when Veronica discovers that he is Trina's father, Moorehead is fired as principal.
==== Van Clemmons ====
Duane Daniels plays Van Clemmons, the vice principal and later principal of Neptune High. During high school, Veronica continually gets into trouble and, as a result, regularly meets with Clemmons. Occasionally, Van Clemmons asks Veronica for help, once asking her to locate the missing school mascot. Clemmons is the one who instructs Veronica to organize some old files, which led to her discovering Moorehead as Trina Echolls' father. When Moorehead is fired as principal, Veronica realizes that Clemmons' plan was all along to become principal. Clemmons says that when Veronica graduates, he cannot decide if his life will be easier or more difficult with her gone. Clemmons reappears in "Un-American Graffiti," where he is caught on tape being shot with a paintball gun by several Neptune High students. He reappears in the film at the reunion where he admits to Veronica that life has been boring since she graduated and makes a brief appearance in the fourth season.
==== Butters Clemmons ====
Adam Hendershott portrays Vincent "Butters" Clemmons, a student at Neptune High and Van Clemmons' son. When he was a freshman, Vincent was pantsed by a bully and named "Butters." Vincent vowed revenge, and that following fall, the jock who had humiliated him and those who did nothing to save him, found themselves having failed mandatory drug tests, essentially barring them from playing sports in their final year of high school. Veronica believed Butters to be behind the crime; however, she discovered the real culprits were a conclave of parents who rigged the drug tests so that their children could gain the spots opened up in the wake of the mass suspension of athletes. Later, when Butters' only friend Marcos Oliveres was killed in the bus crash, and his parents sued the school, Veronica thought Butters was targeting the family, leaving them reminders of their son to torment the parents. She discovers that Butters and Marcos secretly ran the local pirate radio station, "Ahoy, Mateys!", which was infamous for its vicious slandering of the popular cliques at school. Butters tells Veronica that he had little contact with Marcos since the summer when he returned from summer camp and quit the radio show without telling Butters why. Veronica later found out summer camp was an anti-gay camp he was sent to and that the real culprit was Marcos' friend Ryan, who had a crush on Marcos and who sought to make the Oliveres suffer the same way they made their son suffer in regards to his potential homosexuality. Butters develops a crush on Mac, much to her disgust, and she is forced to attend Logan's "anti-prom" with him.
==== Lucky ====
James Jordan portrays Tommy "Lucky" Dohanic, the deceased former janitor at Neptune High. He previously acted as a batboy for Woody Goodman's baseball team, the Sharks. He later stalked Woody's daughter Gia and was later arrested when he attempted to attack her. However, the Mannings bailed Lucky out of jail, and he returned to the school the following day with a toy pistol, searching for Gia. After firing several (blank) bullets, including one at Wallace, he was shot and killed by school security.
==== Corny ====
Jonathan Chesner portrays Douglas "Corny," a Stoner and occasional ally of Veronica's. Corny is in the same graduation class as Veronica. Corny makes the bong that Veronica plants in Logan's locker in "Pilot." Resident stoner of Neptune High. Works at Cho's Pizza as a deliveryman. When he is mugged and tasered in "Versatile Toppings" he helps Veronica find the culprit. He appears to have somewhat of a crush on Veronica, as seen in "Blast from the Past" when he nominates her for Neptune High's Homecoming Queen. He was the DJ in between the Faders's sets at the Homecoming dance senior year. He's very proud of his brownie recipe claiming that "it's all in the butter." He appears to go to Logan's Alterna-Prom alone.
==== Hannah Griffith ====
Jessy Schram plays Hannah Griffith, an "09er" high-school sophomore student at Neptune High. Hannah meets Logan at the school carnival and is surprised when he asks her out. Logan reveals to Hannah that her father, plastic surgeon Dr. Thomas Griffith, is a cocaine user. He tells her that he is protecting his dealers, the Fitzpatricks, and has falsely testified against Logan in a murder trial. Hannah decides that she cannot trust Logan because he is only dating her to get to her father, but she is quick to forgive him. When her father catches her being undressed by Logan, he sends Hannah to a Vermont boarding school.
==== Deborah Hauser ====
Kari Coleman portrays Deborah Hauser, a divorced sex education teacher with a bitter approach to her students, disliking all non-09ers and kissing ass to the 09ers. Veronica baby-sits her demonic son to find out if he is being abused. It is also revealed she was friends with Lianne Mars when they attended Neptune High as teenagers and were suspended together for spreading a "false and malicious rumor." Mrs. Hauser maintained that Lianne told her a rumor, knowing it was false, and Deborah passing it on unknowingly; however, Veronica found out the real story. Lianne's friend had an affair with a teacher at the school and became pregnant, and not knowing how to help, she confided in Deborah, who passed the gossip around. This baby would end up being Trina Echolls. Mrs. Hauser makes another appearance during the Winter Carnival at school, where she steals money from the cashbox and tries to blame Veronica and Jackie. However, she is caught and deservedly fired.
==== Rebecca James ====
Paula Marshall portrays Rebecca James, the school guidance counselor who briefly dated Keith Mars. Paula had previously worked with series creator Rob Thomas on his earlier series, Cupid. Veronica disapproves of their relationship and digs up information on her to change Keith's mind – information being Ms. James was arrested for passing bad checks when she was 21. Ms. James and Veronica's relationship is strained because of this, although she does try to help Veronica discover the meaning of her haunting dreams in the second season.
==== Meg Manning ====
Alona Tal recurs as Meg Manning, an "09er" cheerleader and the daughter of mentally abusive fundamentalist Christian parents. She initially appears when Veronica is the victim of a nasty prank, lends her clothes, and sticks up for her when other 09ers start insulting her. When an online purity test posts all the participants' results, Meg's is faked to be unusually low, and she instantly gets a reputation as a slut. Veronica finds the person responsible for making this up about Meg (in "Like a Virgin"). When Meg asks Veronica to help find her secret admirer, she is keen to help, until she finds out that her secret admirer is Duncan Kane, Veronica's ex-boyfriend. Eventually, Veronica accepts Meg and Duncan's relationship. ("Ruskie Business") After finding out that he is not Veronica's half-brother, Duncan breaks up with Meg, who blames Veronica. Afterward, Meg's attitude towards Veronica is openly hostile. On the way back from a field trip to a baseball ground, while Veronica talked to Weevil during a rest stop, Meg deliberately implied that Veronica had returned to the bus, causing it to leave without her. However, the bus subsequently careened off a cliff and into the ocean. ("Normal Is the Watchword")
Meg was the only survivor, but she remained in a coma for much of the second season. Meg has two younger sisters, Lizzie and Grace. While Meg was in a coma, Lizzie brought Duncan Meg's laptop, asking him to remove Meg's files from the system before her parents were able to check them. Duncan and Veronica found that Meg had compiled information about a child whom she often babysat. His parents were abusing the young boy. Soon, the two uncovered that the abused child (who was referred to by Meg as a boy) was Meg's youngest sister, Grace. Meg's parents are religious zealots who lock Grace in a closet when they are out and make her fill out exercise book after exercise book with the phrase: "The path of God is paved with righteousness." Duncan and Veronica found dozens of these books in Grace's room. Veronica visited Meg in the hospital and discovered that Meg was pregnant with Duncan's child, which was why she was so mad at Veronica. Shortly after she left, Meg awoke from her coma. ("My Mother, the Fiend") Meg later apologizes to Veronica for her harsh treatment towards her and makes her promise not to let the baby end up with her parents if something happens to her. Later that same episode, Meg died of a blood clot to the heart, but not before giving birth to her daughter Faith, whom Duncan later renaming Lilly after fleeing the country with her.
==== Thumper ====
James Molina plays Eduardo "Thumper" Orozco, a PCH biker who betrays Weevil and starts dealing drugs for the Irish gang, the Fitzpatricks. He stabs Felix Toombs under orders from Liam Fitzpatrick for dating Liam's niece and sets up Logan as the culprit. Weevil later realizes Thumper did it, but can't prove it, so he sets up Thumper to make it look like stealing drugs and money from the Fitzpatricks. Liam and his cousin Danny Boyd lock Thumper inside "Shark Stadium" along with his bike, shortly before the building is blown up in a controlled demolition.
==== Carrie Bishop ====
Leighton Meester plays Carrie Bishop, nicknamed the queen of gossip at Neptune High. She appeared in two episodes. She was known for faking an affair with a teacher who Veronica strongly thought was innocent. The teacher found that he had a relationship with a previous student who had his baby, whom he denied and left. That student was the reason why Carrie had made these accusations. She also appeared in a later episode when Veronica is searching for the one responsible for raping her at Shelly Pomeroy's party. Carrie had told her that Duncan Kane was the one she saw with Veronica in the bedroom. Andrea Estella replaced Meester in Carrie's role for the Veronica Mars film, centering around the death of the character. Before the film, Carrie became a self-destructive pop star under the name Bonnie DeVille and began a relationship with Logan. Their relationship turned sour, and Carrie started attending Alcoholics Anonymous meetings with now ex-boyfriend Logan as her sponsor. At the start of the film, she was found dead in her bathtub.
==== Samuel Pope ====
Michael Kostroff portrays Samuel Pope, the teacher of Future Business Leaders of America and one of Neptune's few ethical people. After making a small fortune from real estate investment in Big Dick Casablancas' firm, he plans to retire to a life of sailing during the second season. Veronica discovers that the company is defrauding the investors and encourages Mr. Pope to get rid of his stock before she reports it, but he sadly replies he cannot do this; to get rid of it, he would have to sell it to someone else, and they would pay the price. He sadly admits he cannot do that and cannot retire as planned. It is assumed he continues teaching at Neptune High.
==== Madison Sinclair ====
Amanda Noret plays Madison Sinclair, Dick's ex-girlfriend and Neptune High's resident bitch. Shortly after Lilly's murder, at Shelly Pomeroy's party, Dick dosed Madison's drink with GHB to loosen her up; however, Madison spat in the drink, which she calls "A Trip to the Dentist," and gave it to Veronica. Veronica drank the soda and later had sex with Duncan, who had also unknowingly ingested GHB (given to him by Logan). The following year, Madison rigged the school election to get Duncan Kane elected to student body president. Veronica exposed the plot, which resulted in Madison losing her place on the student council and the position's special privileges. Veronica discovers in Season One that Madison was switched at birth with Mac. It is shown that Madison continually argues with her family.
In contrast, Mac's parents have entirely accepted Mac as their daughter and have shown no signs of wanting anything to do with Madison. After breaking up with Dick, she is secretly involved with Sheriff Don Lamb ("The Rapes of Graff"). Veronica discovers this and mocks Madison about her relationship with Lamb in front of their classmates through innuendo that, while her classmates do not understand, had a meaning that was quite apparent to Madison.
Madison, having gone off to college at USC, is absent from much of Veronica's life at Hearst, until she had several run-ins with her in Neptune in the episode "Poughkeepsie, Tramps and Thieves." Veronica first sees Madison when she arrived unexpectedly at Neptune Grand Suite shared by Logan and Dick; thinking that Madison was simply looking up her ex, Veronica sent her on her way. Later, however, she ran into her again at a lingerie shop where Madison maliciously let slip that she had spent the night with Logan while in Aspen over Christmas break Veronica and Logan were split up. In the following episode, Veronica, consumed by images of Madison's affair with Logan, follows her and eventually plots with Weevil to have Madison's new car crushed and cubed. However, Veronica has a change of heart and asks him to return it unscathed, save for a can of tuna in her air conditioning.
Madison reappears in the Veronica Mars film, attending Neptune High's 10-year reunion. She plays a copy of Veronica and Piz's college sex tape in an attempt to humiliate her, which causes a fight to break out.
==== Felix Toombs ====
Brad Bufanda plays Felix Toombs, Weevil's right-hand man. Bufanda initially tried out for the role of Weevil. Felix is a PCH bike gang member and Weevil's best friend. After the PCH gang beat up Logan for supposedly killing Weevil's lover Lilly Kane, Logan wakes up beside Felix, stabbed to death. Weevil first suspects Logan but later finds out he is innocent and enlists his help to solve the case. Weevil finds out the PCHers had been dealing drugs for the Fitzpatricks behind his back during that time. Felix was secretly dating Molly Fitzpatrick (Liam Fitzpatrick's niece), so Liam ordered Felix's fellow gang member Thumper, who works for the Fitzpatricks, to kill Felix.
==== Troy Vandergraff ====
Aaron Ashmore portrays Troy Vandegraff, a childhood friend of Duncan's, Veronica's boyfriend, for the early stretch of season one. He betrays Veronica and leaves town, but he is somewhat reformed by the time they meet again later in the series. Troy and Veronica dated for a short time in Season One. Their relationship didn't last long because Troy involved an unwitting Veronica in a plot to smuggle steroids from Mexico into the US. Veronica managed to find out his intentions before completing his plan and running away with his real girlfriend. He later comes back in the episode "The Rapes of Graff" in Season 2, where he is accused of raping and shaving the head of a girl at Hearst College. Veronica ended up clearing Troy's name but did not find out who the real rapist is until the third season.
==== Jane Kuhne ====
Valorie Curry plays Jane Kuhne, student-athlete at Neptune High and Wallace's girlfriend after returning from Chicago. She is introduced in Season 1 while Wallace is pursuing Jackie as a distant admirer of Wallace who has been ignored. After Wallace returns from Chicago, he takes up with Jane. She is featured in the episode "The Quick and the Wed" when her older sister disappears following a bachelorette party, and Veronica investigates the disappearance.
=== Hearst College ===
==== Tom Barry ====
Matt McKenzie plays Tom Barry, Wallace's basketball coach and father of Josh Barry. He is allegedly murdered the night after a basketball game during which he fights with Josh, and the team loses the game. Josh is believed to be his killer due to the argument that Mason drove past the area where Coach Barry died and saw someone who appeared to be Josh with him. It is revealed that he was dying of an incurable brain disease that would be slow, painful, humiliating, and costly. He arranged for his suicide to appear as a carjacking so that his family would be paid life insurance (which they would not in the case of suicide) and take care of them financially.
==== Chip Diller ====
David Tom plays Chip Diller, the President of the Pi Sig frat house. He first appears in season two when Veronica visits Hearst, and she accuses him of raping a student. While it turns out he is not a rapist, he is shown to be still a horrible person. A group of campus feminists attacked him, shaved his head, and shoved an egg into his rectum on the anniversary of Patrice Pitrelli's attempted suicide for his part in it. During the episode "Spit & Eggs," Veronica points out to Chip that the beer coasters provided by the Pi Sig's were not sufficient since they were supposed to be used for drug testing, but he does not care. Chip is one of the foremost perpetrators in spreading the sex video of Veronica and Piz; however, it did not have anything to do with its creation.
==== Tim Foyle ====
James Jordan appears as Tim Foyle, a teaching assistant for Professor Hank Landry at Hearst College. Tim seems to dislike Veronica, possibly because Landry seems to prefer her over him. In the first session of Landry's criminology class (in "Welcome Wagon"), he has his students play a detective game, "Murder on the Riverboat Queen." Veronica beats Tim's record time for solving the mystery by ten minutes, then embarrasses and annoys him by saying, "There is one thing I can't figure out: what did you do with the extra ten minutes?" In "Hi, Infidelity," Tim accuses Veronica of plagiarizing her mid-term paper and gives her three days to clear herself. After Veronica figures out what happened, she accuses Tim of setting her up just so that she would discover that Landry was having an affair with Mindy O'Dell, the Dean's wife, but Tim does not explicitly deny it; instead, he says that if he HAD set the whole thing up, it would have been to show Veronica what Landry was really like before she became his protege. Tim is also the boyfriend of Bonnie Capistrano, Dick's fling, and is presumably the father of her miscarried baby. While investigating the truth behind Bonnie's miscarriage, she discovers that Tim was very supportive of her decision to have the baby and that he even asked Bonnie to marry him to please her religious parents. In "Papa's Cabin," Tim and Veronica team up in an attempt to clear Dr. Landry of the murder of Hearst College's Dean of Students, Cyrus O'Dell. At the end of the episode, however, it is revealed that Tim himself murdered Cyrus O'Dell to take revenge on Landry for ruining his chances at a job at (a fictional version of) Pepperdine University, by giving an unfavorable reference to the prospective employer. Tim's name is, in fact, a joke by the writers. His character was created as a foil for Veronica and was referred to as "FOIL" during the early drafts. According to Rob Thomas on the DVD extras, they eventually decided to call him Foyle anyway, and Tim as his first name as a play on "tin foil." Jordan reprises his role in the fourth season episode "Heads You Lose," where Veronica visits him in prison.
==== Max ====
Adam Rose portrays Max, a geeky student who provides test answers for cash. While he started as a one-time guest star, he turned into a recurring character due to his likability. He makes a profit with his business and does not care when he is expelled from Hearst, planning to make his living from it anyway. Max comes to Veronica with the task of finding his dream girl whom he met at ComiCon and had an instant connection with, who left telling him she'd left her details in his hotel room, for him to return and find the hotel cleaners had already been and it had disappeared. It turned out that this girl was a hooker hired by his friends so that Max could lose his virginity; he decides to continue trying to find her even when he finds this out. Max convinced Chelsea to leave the prostitution business for him, and he pays off her $10,000 debt to her pimp. However, things are not the same when her past keeps being brought up; he finally asks whether she left her information, and Chelsea is heartbroken when he realizes she didn't – "But I really wish I had." She leaves but promises to pay him back – it is implied that she is making her money by stripping. Max comes back into the series as Mac's new boyfriend after she breaks up with Bronson for him. Rose reprises his role in the fourth season episode "Heads You Lose."
==== Mercer Hayes ====
Ryan Devlin recurs as Mercer Hayes, a friend of Logan and Dick, who runs an illegal casino out of his dorm room called the Benetian. Parker suspects him of being the rapist due to him wearing the same cologne she smelled the night she was raped, and Veronica investigates and finds he owns an electric razor. She reports this to Lamb, who agrees with her for once, due to seeing the same date rape drugs inside Mercer's money box. However, Logan provides Mercer with an incriminating alibi – they accidentally burnt down a Tijuana motel the night of one of the rapes – but Veronica finds other proof that he didn't do it (his live, call-in radio show being on at the time of one of the rapes). However, when at the Pi Sig party, she hears his show being played and recognizes electronic distortion and skipping, she realizes he is the rapist, the shows being recorded. She prevents him from raping a 5th girl and stabs him with a ceramic unicorn horn, and eventually, Keith arrests Moe and Mercer. He is last seen in a jail cell with Logan (who smashed a police cruiser to get arrested, get put into a cell with Mercer, and get revenge on him for what he did to Veronica and the other girls). Devlin reprises his role in the fourth season episode "Heads You Lose," where Veronica visits him in prison.
==== Hank Landry ====
Patrick Fabian portrays Hank Landry, Veronica's Criminology professor and admirer. He is having an affair with Dean O'Dell's wife Mindy O'Dell and accidentally kills her when framed by his TA Tim Foyle for the murder of the Dean. Hank Landry is Veronica's Intro to Criminology professor. Although Veronica has yet to decide on a major, Prof. Landry has been advocating criminal investigations as a career choice for her. Prof. Landry is joined in his Intro to Criminology class by his teaching assistant Tim Foyle. Veronica first impressed Prof. Landry by solving the murder mystery he presented on the first day of class in record time. Later, she impresses him by being the sole person to write an "A" caliber paper on his "Perfect Murder" assignment. After reading the paper, he talks to Veronica about her potential and offers her faculty adviser. While Veronica is considering Prof. Landry's offer, she is manipulated by Tim Foyle into finding out one of Landry's secrets: he has been having an affair with Mindy O'Dell, the wife of the Dean of Hearst College. Shortly after this incident, Prof Landry announces his end-of-term research paper: to plan the perfect murder. He then meets with Veronica and tells her that he will recommend her for a summer internship with the FBI and that he will accept her application essay for the position as a replacement for the end-of-term assignment. Veronica assumed that Prof. Landry was attempting to buy her silence about Landry's affair with Mindy and turned down the offer. Upon telling this to Prof. Landry, he explained that the internship offer had nothing to do with what she knew about him, but Veronica still opted to write the end-of-term paper. Veronica received one of the three "A"s that Prof. Landry gave out for this paper. When Veronica finds out that her father is investigating whether Dean O'Dell's wife is having an affair, she tells Keith what she knows about Prof. Landry and Mindy. Keith tells the Dean, who takes a loaded revolver and visits Prof. Landry and Mindy O'Dell in the middle of one of their rendezvous. It is as of now unknown what transpired in the room that night. When Keith takes the Dean O'Dell case, he finds Prof. Landry at a local bar and attempts to entice Landry's confession over some drinks. However, this does not work as Landry informs Keith that he read Keith's book and he knows that Keith is a private investigator.
==== Claire Nordhouse ====
Krista Kalmus plays Claire Nordhouse, a feminist and member of Lillith house, friends with Nish and Fern. She is one of the protestors who made a front-page newspaper picture of many topless women holding a banner reading, "We go to Hearst, go ahead and rape us!" Claire is beautiful, with long blonde hair, making her the target of the rival newspaper's response (topless men holding a banner saying "No thanks! (except maybe the blonde in the middle)"). The three use this response to have the Pi Sig house shut down and the rival newspaper run by them by faking Claire's rape. However, Veronica finds out that it was not real and exposes this – ATM photos showing the guy with her before her rape, who took her home, was Claire's boyfriend who helped set it up. She is then expelled from Hearst as a result. She was Patrice Pitrelli's best friend in their freshman year and was the source of information about the Theta Beta two-way mirror.
==== Cyrus O'Dell ====
Ed Begley, Jr. portrays Cyrus O'Dell, the Dean of Hearst College. Initially, Veronica's adversary, gradually becoming her ally and gaining her respect, and vice versa. Married to much younger Mindy, he suspects her of having an affair, which Keith later proves to be with Hank Landry. He confronts the two, threatening to leave her broke and ruin Landry's career. Tim Foyle kills him during the ninth episode in Veronica's Plan a Perfect Murder paper (a fake suicide). After his death, it is revealed that he wrote her a referral to the FBI, a statement of what a brilliant student she was and how he had not encountered a student with more talent in all his years in academia. His body is found by Weevil, who is rather gutted, having grown quite fond of the dean while working at Hearst.
==== Bronson Pope ====
Michael Mitchell plays Bronson Pope, an animal rights activist and Mac's first post-Cassidy boyfriend. He is shown to be extremely outdoorsy, encouraging Mac to play Ultimate Frisbee and take early morning hikes. She loses her virginity on Valentine's Day but breaks up with him not much later after falling for Max.
==== Moe Slater ====
Andrew McClain portrays Moe Slater, the R.A. of the Hearst College dorms. He is very earnest and is always offering oolong tea to everyone – implied to be how he drugs people. Mercer's partner helped him rape the girls as he was the Safe Ride Home driver. He would take drunk girls home (it is still unclear whether he drugged them at the party or drugged them once they were in their dorms) and then tell Mercer which room and provide him the keys to get in. The relationship between him and Mercer is implied to result from the prison warden experiment that Logan and Wallace underwent. He keeps a photo of the two of them in their uniforms. Moe was the prisoner, and Mercer, the warden, mentally dominated him and controlled him to rape. It was Moe that drugged Veronica and tried to shave her head to give Mercer an alibi.
==== Nish Sweeney ====
Chastity Dotson portrays Nancy "Nish" Sweeney, the former Editor of the Hearst Free Press and feminist of Lillith House. She and Veronica are initially friends when she gives Veronica the assignment to go undercover and infiltrate the Theta Beta sorority house. Veronica is supposed to find proof of a two-way mirror in which Theta Betas would make the rushes undress in front of for the Pi Sigs enjoyment. However, Nish publishes the article that Veronica asked her not to write about a cannabis farm at the sorority house, and they become enemies. Nish helps Claire fake the rape and eggs Dean O'Dell's window the night he was murdered. By the end of the semester, Nish and Veronica are on good terms, as Veronica gives her a list of names of members of the secret fraternity, the Castle.
==== Blake Long ====
Spencer Ward plays Blake Long, a Pi Sig member in the fourth season, involved in a mysterious cover-up that may be connected to the Neptune Spring Break bombings.
== Other characters ==
The following is a supplementary list of recurring or one-time guest stars, which includes characters that appear briefly in multiple episodes but have little to no real-world content to justify an entire section covering their in-universe histories.
Steve Rankin portrays Lloyd Blankenship, a newspaper reporter and ally of Keith.
Taylor Sheridan plays Danny Boyd, Liam Fitzpatrick's dim-witted cousin and accomplice.
Kate McNeil plays Betina Casablancas, Dick and Cassidy's biological mother.
Brandon Hillock plays Jerry Sacks, Sheriff Lamb's right-hand man.
Annie Campbell plays Molly Fitzpatrick, a member of the Fitzpatrick family and Felix's girlfriend until his death.
Kevin Sheridan plays Sean Friedrich, an "09er" with a penchant for thievery and drug dealing.
Cher Ferreyra portrays Fern Delgado, a disgruntled feminist and member of the "Take Back the Night" program. She lives in Lillith house with Nish and Claire and dislikes Veronica for proving the Pi Sigs weren't rapists. Veronica initially suspects her in the disappearance of Selma Hearst Rose.
Robert Ri'Chard plays Mason, a hot-tempered basketball jock and Wallace's new friend. He encourages Wallace to skip studying to hang out with him and instead puts him in contact with Max to cheat. He is the one who mistakes Josh as being the person out on the overlook with Coach Barry before he is killed.
Joss Whedon plays Douglas, a clueless car-rental salesman who inadvertently helps Veronica track down Abel Koontz' daughter Amelia Delongpre in the episode "Rat Saw God."
Logan Miller and Ashton Moio play Simon and Craig, two college students and Spring Breakers whose friendship with a bombing victim is a source of clues for Mars Investigations.
== References ==
== External links ==
Complete Episode, Soundtrack, and Character Information
Veronica Mars CWiki on CWTV.com
Veronica Mars on Warnerbros.com
Full cast and crew of Veronica Mars at IMDb | Veronica Mars is an American television series created by Rob Thomas. The series premiered on September 22, 2004, during network UPN's last two years, and ended on May 22, 2007, after a season on UPN's successor network, The CW. Balancing murder mystery, high-school, and college drama, the series features social commentary with sarcasm and off-beat humor in a style often compared to film noir. Set in the fictional town of Neptune, the series stars Kristen Bell as the title character, a student who progresses from high school to college during the series while moonlighting as a private investigator under the wing of her detective father.
The first season had seven regular characters. However, Thomas decided to introduce and eliminate several characters in order to create an "equally fascinating mystery" for the series' second season. Thomas needed "new blood" since he felt unable to bring back the Kanes and the Echolls and "have them all involved in a new mystery". The third season features a cast of ten actors who receive billing, an increase from the nine actors in the second. Three of the regulars in the second season are written out of the series, two new characters are introduced and two others are upgraded from recurring roles.
| 8 |
359 | mac | Mac, Birmingham (wikipedia) | Midlands Arts Centre also known as MAC is a non-profit contemporary arts centre situated in Cannon Hill Park, Edgbaston, Birmingham, England. It was established in 1962 and is registered as an arts charity . It presents a dynamic programme of art exhibitions, independent cinema, live performances and creative courses for all ages as well as offering spaces for hire within the building .
The centre re-opened in May 2010 after a £15m facelift. It has four performance spaces, rehearsal, media and recording studios, a 150 seat cinema, café, bar and 4 art gallery spaces. In 2022, MAC was voted the most visited free attraction in the West Midlands by VisitEngland.
== History ==
The idea for an arts centre in Cannon Hill Park was the result of a meeting between local residents: theatre writer and director John English, his wife, Mollie Randle, and local politician Frank Price in the late 1950s. Eventually 8.6 acres (3.5 ha) of land in Cannon Hill Park was made available by Birmingham City Council in 1962 for this purpose. It also housed the Cannon Hill Puppet Theatre under John M. Blundall. The foundation stone for the new arts centre was laid on 19 June 1962 by six people representing those for whom the centre was intended.
In 1965 director Mike Leigh went to work at the theatre and started experimenting with the idea that writing and rehearsing could potentially be part of the same process. Between 1972 and 1987 it was the home of the former Birmingham Youth Theatre, a company aimed at encouraging and nurturing talent amongst people aged 15 to 23 who were not involved with drama or theatre. This company was founded by local teacher Derek Nicholls, who later became Director of the mac. Adrian Lester and Andrew Tiernan began their careers there.
Other artists who performed here include Yoko Ono, Kate Malone, and Ewen Henderson; and renowned musicians and bands such as Ruby Turner, Ocean Colour Scene, UB40, and ELO played at MAC in the early stages of their career. Indian classical dancer Nahid Siddiqui taught Kathak classes here, and famous Bharatanatyam exponent Chitra Bolar started teaching at MAC in 1978. Their contributions established MAC as a centre for South Asian dance and performing arts.
The centre closed from April 2008 to 1 May 2010 for a £14.8 million refurbishment.
== References ==
== External links ==
Official website | Midlands Arts Centre also known as MAC is a non-profit contemporary arts centre situated in Cannon Hill Park, Edgbaston, Birmingham, England. It was established in 1962 and is registered as an arts charity . It presents a dynamic programme of art exhibitions, independent cinema, live performances and creative courses for all ages as well as offering spaces for hire within the building .
The centre re-opened in May 2010 after a £15m facelift. It has four performance spaces, rehearsal, media and recording studios, a 150 seat cinema, café, bar and 4 art gallery spaces. In 2022, MAC was voted the most visited free attraction in the West Midlands by VisitEngland. | 5 |
360 | mac | McIntosh (apple) (wikipedia) | The McIntosh ( MAK-in-tosh), McIntosh Red, or colloquially the Mac, is an apple cultivar, the national apple of Canada. The fruit has red and green skin, a tart flavour, and tender white flesh, which ripens in late September. In the 20th century, it was the most popular cultivar in Eastern Canada and New England, and is considered an all-purpose apple, suitable both for cooking and eating raw.
John McIntosh discovered the original McIntosh sapling on his Dundela farm in Upper Canada in 1811. He and his wife cultivated it, and the family started grafting the tree and selling the fruit in 1835. In 1870, it entered commercial production, and became common in northeastern North America after 1900. While still important in production, the fruit's popularity fell in the early 21st century in the face of competition from varieties such as the Gala. According to the US Apple Association website, it is one of the fifteen most popular apple cultivars in the United States.
Apple Computer employee Jef Raskin named the Macintosh computer line after the cultivar.
== Description ==
The McIntosh, or McIntosh Red (nicknamed the "Mac"), is the most popular apple cultivar in eastern Canada and the northeastern United States. It also sells well in Eastern Europe.
A spreading tree that is moderately vigorous, the McIntosh bears annually or in alternate years. The tree is hardy to at least USDA Hardiness zone 4a, or −34 °C (−29 °F). 50% or more of its flowers die at −3.1 °C (26.4 °F) or below.
The McIntosh apple is a small to medium-sized round fruit with a short stem. It has a red and green skin that is thick, tender, and easy to peel. Its white flesh is sometime tinged with green or pink and is juicy, tender, and firm, soon becoming soft. The flesh is easily bruised.
The fruit is considered "all-purpose", suitable both for eating raw and for cooking. It is used primarily for dessert, and requires less time to cook than most cultivars. It is usually blended when used for juice.
The fruit grows best in cool areas where nights are cold and autumn days are clear; otherwise, it suffers from poor colour and soft flesh, and tends to fall from the tree before harvest. It stores for two to three months in air, but is prone to scald, flesh softening, chilling sensitivity, and coprinus rot. It can become mealy when stored at temperatures below 2 °C (36 °F). The fruit is optimally stored in a controlled atmosphere in which temperatures are between 1.7 and 3.0 °C (35.1 and 37.4 °F), and air content is 1.5–4.5% oxygen and 1–5% carbon dioxide; under such conditions, the McIntosh will keep for five to eight months.
== Cultivation ==
The McIntosh is most commonly cultivated in Canada, the United States, and Eastern Europe. It is one of the top five apple cultivars used in cloning, and research indicates the McIntosh combines well for winter hardiness.
If unsprayed, the McIntosh succumbs easily to apple scab, which may lead to entire crops being unmarketable. It has generally low susceptibility to fire blight, powdery mildew, cedar-apple rust, quince rust, and hawthorn rust. It is susceptible to fungal diseases such as Nectria canker, brown rot, black rot, race 1 of apple rust (but resists race 2). Furthermore, it is moderately resistant to Pezicula bark rot and Alternaria leaf blotch, and resists brown leaf spots well.
The McIntosh is one of the most common cultivars used in apple breeding; a 1996 study found that the McIntosh was a parent in 101 of 439 cultivars selected, more than any other founding clone. It was used in over half of the Canadian cultivars selected, and was used extensively in the United States and Eastern Europe as well; rarely was it used elsewhere. Offspring of the McIntosh include: the Jersey Black hybrid the Macoun, the Newtown Pippin hybrid the Spartan, the Cortland; the Empire; the Jonamac, the Jersey Mac, the Lobo, the Melba, the Summered, the Tydeman's Red, and possibly the Paula Red.
== History ==
Apple trees were introduced to Canada at the Habitation at Port-Royal as early as 1606 by French settlers. Following its introduction, apple cultivation spread inland.
The McIntosh's discoverer, John McIntosh (1777 – c. 1845–46), left his native Mohawk Valley home in New York State in 1796 to follow his love, Dolly Irwin, who had been taken to Upper Canada by her Loyalist parents. She had died by the time he found her, but he settled as a farmer in Upper Canada. He married Hannah Doran in 1801, and they farmed along the Saint Lawrence River until 1811, when McIntosh exchanged the land he had with his brother-in-law Edward Doran for a plot in Dundela.
While clearing the overgrown plot, McIntosh discovered some apple seedlings on his farm. Since the crabapple was the only native apple in North America before European settlement, it must have had European origins. The Snow Apple (or Fameuse) had been popular in Lower Canada before that time; the seedlings may have sprouted from discarded fruit. Fall St Lawrence and Alexander have also been proposed, but the parentage remains unknown. He transplanted the seedlings next to his house. One of the seedlings bore particularly good fruit. The McIntosh grandchildren dubbed the fruit it produced "Granny's apple", as they often saw their grandmother taking care of the tree in the orchard. McIntosh was selling seedlings from the tree by 1820, but they did not produce fruit of the quality of the original.
John McIntosh's son Allan (1815–1899) learned grafting about 1835; with this cloning, the McIntoshes could maintain the distinctive properties of the fruit of the original tree. Allan and brother Sandy (1825–1906), nicknamed "Sandy the Grafter", increased production and promotion of the cultivar. Earliest sales were in 1835, and in 1836 the cultivar was renamed the "McIntosh Red"; it entered commercial production in 1870. The apple became popular after 1900, when the first sprays for apple scab were developed. A house fire damaged the original McIntosh tree in 1894; it last produced fruit in 1908, and died and fell over in 1910.
Horticulturist William Tyrrell Macoun of the Central Experimental Farm in Ottawa is credited with popularizing the McIntosh in Canada. He stated the McIntosh needed "no words of praise", that it was "one of the finest appearing and best dessert apples grown". The Macoun, a hybrid of the McIntosh and Jersey Black grown by the Agricultural Experiment Station in Geneva, NY, was named for him in 1923. In the northeastern United States, the McIntosh replaced many Baldwins that were killed in a severe winter in 1933–34. In the late 1940s, Canadian ambassador to the United Nations Andrew McNaughton told the Soviet Minister for Foreign Affairs Andrei Gromyko that the McIntosh Red was Canada's best apple.
The McIntosh made up 40% of the Canadian apple market by the 1960s; and at least thirty varieties of McIntosh hybrid were known by 1970. Its popularity later waned in the face of competition from imports; in the first decade of the 21st century, the Gala accounted for 33% of the apple market in Ontario to the McIntosh's 12%, and the Northern Spy had become the preferred apple for pies. Production remained important to Ontario, however, as 30,000,000 kilograms (66,000,000 lb) of McIntoshes were produced in 2010.
The original tree discovered by John McIntosh bore fruit for more than ninety years, and died in 1910. Horticulturalists from the Upper Canada Village heritage park saved cuttings from the last known first-generation McIntosh graft before it died in 2011 for producing clones.
=== Descendant Cultivars ===
O.P. = Open Pollinated
== Cultural significance ==
The McIntosh has been designated the national apple of Canada. A popular subscription funded a plaque placed 100 metres (110 yd) from the original McIntosh tree in 1912. The Ontario Archaeological and Historic Sites Board replaced the plaque with a more descriptive one in 1962, and the Historic Sites and Monuments Board of Canada put up another in a park nearby in 2001, by a painted mural commemorating the fruit.
Apple Inc. employee Jef Raskin named the Macintosh line of personal computers after the McIntosh. He deliberately misspelled the name to avoid conflict with the hi-fi equipment manufacturer McIntosh Laboratory. Apple's attempt in 1982 to trademark the name Macintosh was nevertheless denied due to the phonetic similarity between Apple's product and the name of the hi-fi manufacturer. Apple licensed the rights to the name in 1983, and bought the trademark in 1986.
In 1995, the Royal Canadian Mint commissioned Toronto artist Roger Hill to design a commemorative silver dollar for release in 1996. Mint engraver Sheldon Beveridge engraved the image of a group of three McIntoshes and a McIntosh blossom, which adorn one side with a ribbon naming the variety. An inscription on the edge reads "1796 Canada Dollar 1996". Issued sheathed in a silver cardboard sleeve in a black leatherette case, 133,779 pieces of the proof were sold, as well as 58,834 pieces of the uncirculated version in a plastic capsule and silver sleeve.
Big McIntosh (Big Mac for short) from the series My Little Pony: Friendship is Magic was named after this apple, like all other Apple Family members were named after other apple-based products
== See also ==
List of Canadian inventions and discoveries
Ambrosia (apple)
Jubilee apple
Spartan (apple)
Wijcik McIntosh
== Notes ==
== References ==
== Works cited ==
== External links ==
Macintosh Apples, Archives of Ontario YouTube channel
Ontario Plaques: John McIntosh
"UK National Fruit Collection".
"Oldest McIntosh apple tree descendant cut down". CBC News.
"Where does the McIntosh Apple Come From?". mysteriesofcanada.com. | The McIntosh ( MAK-in-tosh), McIntosh Red, or colloquially the Mac, is an apple cultivar, the national apple of Canada. The fruit has red and green skin, a tart flavour, and tender white flesh, which ripens in late September. In the 20th century, it was the most popular cultivar in Eastern Canada and New England, and is considered an all-purpose apple, suitable both for cooking and eating raw.
John McIntosh discovered the original McIntosh sapling on his Dundela farm in Upper Canada in 1811. He and his wife cultivated it, and the family started grafting the tree and selling the fruit in 1835. In 1870, it entered commercial production, and became common in northeastern North America after 1900. While still important in production, the fruit's popularity fell in the early 21st century in the face of competition from varieties such as the Gala. According to the US Apple Association website, it is one of the fifteen most popular apple cultivars in the United States.
Apple Computer employee Jef Raskin named the Macintosh computer line after the cultivar. | 8 |
361 | mac | Message authentication code (wikipedia) | In cryptography, a message authentication code (MAC), sometimes known as an authentication tag, is a short piece of information used for authenticating and integrity-checking a message. In other words, to confirm that the message came from the stated sender (its authenticity) and has not been changed (its integrity). The MAC value allows verifiers (who also possess a secret key) to detect any changes to the message content.
== Terminology ==
The term message integrity code (MIC) is frequently substituted for the term MAC, especially in communications to distinguish it from the use of the latter as media access control address (MAC address). However, some authors use MIC to refer to a message digest, which aims only to uniquely but opaquely identify a single message. RFC 4949 recommends avoiding the term message integrity code (MIC), and instead using checksum, error detection code, hash, keyed hash, message authentication code, or protected checksum.
== Definitions ==
Informally, a message authentication code system consists of three algorithms:
A key generation algorithm selects a key from the key space uniformly at random.
A signing algorithm efficiently returns a tag given the key and the message.
A verifying algorithm efficiently verifies the authenticity of the message given the same key and the tag. That is, return accepted when the message and tag are not tampered with or forged, and otherwise return rejected.
A secure message authentication code must resist attempts by an adversary to forge tags, for arbitrary, select, or all messages, including under conditions of known- or chosen-message. It should be computationally infeasible to compute a valid tag of the given message without knowledge of the key, even if for the worst case, we assume the adversary knows the tag of any message but the one in question.
Formally, a message authentication code (MAC) system is a triple of efficient algorithms (G, S, V) satisfying:
G (key-generator) gives the key k on input 1n, where n is the security parameter.
S (signing) outputs a tag t on the key k and the input string x.
V (verifying) outputs accepted or rejected on inputs: the key k, the string x and the tag t.
S and V must satisfy the following:
Pr [ k ← G(1n), V( k, x, S(k, x) ) = accepted ] = 1.
A MAC is unforgeable if for every efficient adversary A
Pr [ k ← G(1n), (x, t) ← AS(k, · )(1n), x ∉ Query(AS(k, · ), 1n), V(k, x, t) = accepted] < negl(n),
where AS(k, · ) denotes that A has access to the oracle S(k, · ), and Query(AS(k, · ), 1n) denotes the set of the queries on S made by A, which knows n. Clearly we require that any adversary cannot directly query the string x on S, since otherwise a valid tag can be easily obtained by that adversary.
== Security ==
While MAC functions are similar to cryptographic hash functions, they possess different security requirements. To be considered secure, a MAC function must resist existential forgery under chosen-message attacks. This means that even if an attacker has access to an oracle which possesses the secret key and generates MACs for messages of the attacker's choosing, the attacker cannot guess the MAC for other messages (which were not used to query the oracle) without performing infeasible amounts of computation.
MACs differ from digital signatures as MAC values are both generated and verified using the same secret key. This implies that the sender and receiver of a message must agree on the same key before initiating communications, as is the case with symmetric encryption. For the same reason, MACs do not provide the property of non-repudiation offered by signatures specifically in the case of a network-wide shared secret key: any user who can verify a MAC is also capable of generating MACs for other messages. In contrast, a digital signature is generated using the private key of a key pair, which is public-key cryptography. Since this private key is only accessible to its holder, a digital signature proves that a document was signed by none other than that holder. Thus, digital signatures do offer non-repudiation. However, non-repudiation can be provided by systems that securely bind key usage information to the MAC key; the same key is in the possession of two people, but one has a copy of the key that can be used for MAC generation while the other has a copy of the key in a hardware security module that only permits MAC verification. This is commonly done in the finance industry.
== Implementation ==
MAC algorithms can be constructed from other cryptographic primitives, like cryptographic hash functions (as in the case of HMAC) or from block cipher algorithms (OMAC, CCM, GCM, and PMAC). However many of the fastest MAC algorithms, like UMAC-VMAC and Poly1305-AES, are constructed based on universal hashing.
Intrinsically keyed hash algorithms such as SipHash are also by definition MACs; they can be even faster than universal-hashing based MACs.
Additionally, the MAC algorithm can deliberately combine two or more cryptographic primitives, so as to maintain protection even if one of them is later found to be vulnerable. For instance, in Transport Layer Security (TLS) versions before 1.2, the input data is split in halves that are each processed with a different hashing primitive (SHA-1 and SHA-2) then XORed together to output the MAC.
=== One-time MAC ===
Universal hashing and in particular pairwise independent hash functions provide a secure message authentication code as long as the key is used at most once. This can be seen as the one-time pad for authentication.
The simplest such pairwise independent hash function is defined by the random key, key = (a, b), and the MAC tag for a message m is computed as tag = (am + b) mod p, where p is prime.
More generally, k-independent hashing functions provide a secure message authentication code as long as the key is used less than k times for k-ways independent hashing functions.
Message authentication codes and data origin authentication have been also discussed in the framework of quantum cryptography. By contrast to other cryptographic tasks, such as key distribution, for a rather broad class of quantum MACs it has been shown that quantum resources do not offer any advantage over unconditionally secure one-time classical MACs.
== Standards ==
Various standards exist that define MAC algorithms. These include:
FIPS PUB 113 Computer Data Authentication, withdrawn in 2002, defines an algorithm based on DES.
FIPS PUB 198-1 The Keyed-Hash Message Authentication Code (HMAC)
NIST SP800-185 SHA-3 Derived Functions: cSHAKE, KMAC, TupleHash, and ParallelHash
ISO/IEC 9797-1 Mechanisms using a block cipher
ISO/IEC 9797-2 Mechanisms using a dedicated hash-function
ISO/IEC 9797-3 Mechanisms using a universal hash-function
ISO/IEC 29192-6 Lightweight cryptography - Message authentication codes
ISO/IEC 9797-1 and -2 define generic models and algorithms that can be used with any block cipher or hash function, and a variety of different parameters. These models and parameters allow more specific algorithms to be defined by nominating the parameters. For example, the FIPS PUB 113 algorithm is functionally equivalent to ISO/IEC 9797-1 MAC algorithm 1 with padding method 1 and a block cipher algorithm of DES.
== An example of MAC use ==
In this example, the sender of a message runs it through a MAC algorithm to produce a MAC data tag. The message and the MAC tag are then sent to the receiver. The receiver in turn runs the message portion of the transmission through the same MAC algorithm using the same key, producing a second MAC data tag. The receiver then compares the first MAC tag received in the transmission to the second generated MAC tag. If they are identical, the receiver can safely assume that the message was not altered or tampered with during transmission (data integrity).
However, to allow the receiver to be able to detect replay attacks, the message itself must contain data that assures that this same message can only be sent once (e.g. time stamp, sequence number or use of a one-time MAC). Otherwise an attacker could – without even understanding its content – record this message and play it back at a later time, producing the same result as the original sender.
== See also ==
Checksum
CMAC
HMAC (hash-based message authentication code)
MAA
MMH-Badger MAC
Poly1305
Authenticated encryption
UMAC
VMAC
SipHash
KMAC
== Notes ==
== References ==
Goldreich, Oded (2001), Foundations of cryptography I: Basic Tools, Cambridge: Cambridge University Press, ISBN 978-0-511-54689-1
Goldreich, Oded (2004), Foundations of cryptography II: Basic Applications (1. publ. ed.), Cambridge [u.a.]: Cambridge Univ. Press, ISBN 978-0-521-83084-3
Pass, Rafael, A Course in Cryptography (PDF), retrieved 31 December 2015
== External links ==
RSA Laboratories entry on MACs
Ron Rivest lecture on MACs | In cryptography, a message authentication code (MAC), sometimes known as an authentication tag, is a short piece of information used for authenticating and integrity-checking a message. In other words, to confirm that the message came from the stated sender (its authenticity) and has not been changed (its integrity). The MAC value allows verifiers (who also possess a secret key) to detect any changes to the message content. | 2 |
362 | mac | Money Access Center (wikipedia) | Money Access Center (MAC, also Money Access Card) was an ATM network in the Mid-Atlantic and Midwestern United States, between 1979 and 2005, when it was absorbed into the STAR network. The network was one of the first in the nation, and helped universalize ATM banking. At its height MAC operated 59,000 ATMs in Pennsylvania, New Jersey, Delaware, Maryland, West Virginia, Kentucky, Ohio, and Michigan.
== History ==
=== Creation ===
MAC was launched in 1979 by the Philadelphia National Bank (PNB), later renamed CoreStates, to compete with the GEORGE network, which was launched one year earlier by Girard Bank. PNB was able to line up support from thirteen other financial institutions at launch, capturing significantly more market share than GEORGE, to the point that the locals preferred the terms "MAC machine" and "MAC card" to "ATM" or "ATM card".
=== Growth and Independence ===
In 1988 CoreStates acquired and integrated MAC competitor CashStream, making MAC the second-largest regional ATM network, behind only NYCE. In 1992 CoreStates created a holding company for MAC, called Electronic Payment Services (EPS), headquartered in Wilmington, Delaware. The company was co-owned by CoreStates, Bank One, PNC Bank, and Society Corporation. These were later joined by KeyCorp and National City Corp.
=== Acquisition and Merger with STAR ===
Through the 1990s EPS expressed its desire to go public, either by issuing an IPO or by being acquired by a publicly traded company. The latter happened in 1999 when publicly-traded Concord EFS acquired EPS for $920 Million. This turned out to be a very profitable deal for Concord, so it acquired two more ATM networks in the next two years, Cash Station and STAR, which expanded Concord's networks to 28 states. In its press-release about the acquisition of STAR in 2001 Concord announced its intent to consolidate the three networks under the STAR banner due to STAR's better name recognition, making STAR the largest ATM network in the country. The MAC (and Cash Station) banner was to be phased out over a period of four years
=== Revival of the Name ===
In 2014, JetPay, founded by Bipin Shah, who ran the MAC network while working at CoreStates, announced a product called Money Access Card, a reloadable payment card for JetPay's payroll-processing-company clients
== Legacy ==
MAC Machine and MAC Card continue to be used to refer to ATMs and ATM cards respectively as a regionalism in certain parts of Pennsylvania and New Jersey, along with the phrase tap MAC to describe getting money from an ATM.
== References == | Money Access Center (MAC, also Money Access Card) was an ATM network in the Mid-Atlantic and Midwestern United States, between 1979 and 2005, when it was absorbed into the STAR network. The network was one of the first in the nation, and helped universalize ATM banking. At its height MAC operated 59,000 ATMs in Pennsylvania, New Jersey, Delaware, Maryland, West Virginia, Kentucky, Ohio, and Michigan. | 2 |
363 | mac | Mạc (wikipedia) | Mạc (chữ Hán: 莫) is a Vietnamese surname. The name is transliterated as Mo in Chinese and Mua in Hmong language. It is also of Gaelic origin, meaning son, used as a prefix in many Irish and Scottish surnames e.g. MacDonald, and MacGregor.
Mac is the anglicised variation of the surname Mạc.
== Distribution ==
As a surname, Mac is the 409th most common surname, in Great Britain, with 23,149 bearers. It is most common in the Aberdeen City council area, and Greater Manchester, where it is the 25th and 107th most common surname, in both counties having 3,268 bearers, respectively. Other concentrations include, the Western Isles, (13th,1,712), East Lothian, (63rd,1,698), the Glasgow City council area, (90th,3,188), County Down, (147th,1,686), East Sussex, (247th,1,646), Belfast, (266th,1,682), Berkshire, (383rd,1,696), South Yorkshire, (466th,1,626), Merseyside, (490th,1,624), and Greater London, (1,189th,1,730).
== Notable people with the surname Mạc ==
Mạc Đĩnh Chi, Vietnamese scholar and official of the Trần dynasty (1272–1346)
Mạc Cửu, a Chinese adventurer who played a role in relations between Cambodia and the Nguyễn court
Mạc dynasty, ruled the northern provinces of Vietnam from 1527 until 1592
Mạc Đăng Dung, Vietnamese emperor and the founder of the Mạc dynasty (1483–1541)
Mạc Đăng Doanh, Vietnamese emperor and the second emperor of the Mạc dynasty (?–1540)
Mạc Hiến Tông, Vietnamese emperor and the third emperor of the Mạc dynasty (?–1546)
Mạc Tuyên Tông, Vietnamese emperor and the fourth emperor of the Mạc dynasty (?–1561)
Mạc Mậu Hợp, Vietnamese emperor and the fifth emperor of the Mạc dynasty (1560–1592)
== Notable people with the surname Mac ==
Alison Mac, British actress
Bernie Mac, American comedian
Annie Mac, Irish DJ and presenter | Mạc (chữ Hán: 莫) is a Vietnamese surname. The name is transliterated as Mo in Chinese and Mua in Hmong language. It is also of Gaelic origin, meaning son, used as a prefix in many Irish and Scottish surnames e.g. MacDonald, and MacGregor.
Mac is the anglicised variation of the surname Mạc. | 3 |
364 | mac | Stanley McMurtry (wikipedia) | Stanley McMurtry MBE (born 4 May 1936), known by his pen name Mac, is a British editorial cartoonist. McMurtry is best known for his controversial work for the British Daily Mail newspaper from 1971 to 2018.
== Career ==
McMurtry was born in Edinburgh on 4 May 1936. His family moved to Birmingham when he was eight years old and he studied at Birmingham College of Art. He undertook National Service with the Royal Army Ordnance Corps from 1954 to 1956.
He adopted the pen name "Mac" while working as a cartoonist for the Daily Sketch in the 1960s. That publication was absorbed by the Daily Mail in 1971, and he worked there for the rest of his career. McMurty was appointed a Member of the Order of the British Empire (MBE) in the 2004 New Year Honours for "services to the newspaper industry".
McMurtry's comic strip Percy's Pets was a regular feature in Smash! from 1966 to c. 1970.
He appeared as a castaway on the BBC Radio programme Desert Island Discs on 23 March 2008.
== Work ==
McMurtry viewed his role as making "dreary news copy of the daily paper brighter, by putting in a laugh", and claimed that his work was apolitical despite its frequent engagement with issues of race, gender, and sexuality. His practice was to produce three or more drafts each day, on differing topics, from which his editor would choose one to be drawn to finished standard. In most of his daily cartoons, Mac included a small portrait of his wife hidden within the picture.
== Controversy ==
McMurtry's cartoons have frequently drawn condemnation for alleged homophobia, racism, and sexism.
In 2001, the British Medical Association received an apology from the Daily Mail for its publication of a McMurtry cartoon which depicted a black, immigrant "witch doctor" jumping on the bed of a shocked, white NHS patient.
In November 2015, Mac was accused of "spectacular racism" for his cartoon featuring caricatures of African tribes people selling shrunken heads, which referred to the news that singer Tom Jones would undergo tests to discover whether he had black ancestry. Later the same month, following the Paris attacks by Jihadists, Mac produced a cartoon depicting refugees with exaggerated noses crossing the EU's borders with rats at their feet. Some journalists suggested the cartoon evoked antisemitic imagery used by Nazi propagandists, including in their notorious film The Eternal Jew (1940).
== Retirement ==
Mac retired from the Daily Mail in December 2018. His last cartoon, published on 20 December, was autobiographical, depicting Mac physically resisting being forced into the "Sunset Home for Retired Cartoonists". An eight-page supplement commemorating his work had been included in the previous day's edition of the paper.
Mac came out of retirement in December 2020 to work for the Mail on Sunday.
== Publications ==
Bryant, Mark; McMurtry, Stanley (2018). 50 years of MAC: a half century of British life. Little, Brown. ISBN 978-1472141620.
== References ==
== External links ==
Stan McMurtry at the British Cartoon Archive, University of Kent | Stanley McMurtry MBE (born 4 May 1936), known by his pen name Mac, is a British editorial cartoonist. McMurtry is best known for his controversial work for the British Daily Mail newspaper from 1971 to 2018. | 1 |
365 | cancer immunology | Cancer immunology (wikipedia) | Cancer immunology (immuno-oncology) is an interdisciplinary branch of biology and a sub-discipline of immunology that is concerned with understanding the role of the immune system in the progression and development of cancer; the most well known application is cancer immunotherapy, which utilises the immune system as a treatment for cancer. Cancer immunosurveillance and immunoediting are based on protection against development of tumors in animal systems and (ii) identification of targets for immune recognition of human cancer.
== Definition ==
Cancer immunology is an interdisciplinary branch of biology concerned with the role of the immune system in the progression and development of cancer; the most well known application is cancer immunotherapy, where the immune system is used to treat cancer. Cancer immunosurveillance is a theory formulated in 1957 by Burnet and Thomas, who proposed that lymphocytes act as sentinels in recognizing and eliminating continuously arising, nascent transformed cells. Cancer immunosurveillance appears to be an important host protection process that decreases cancer rates through inhibition of carcinogenesis and maintaining of regular cellular homeostasis. It has also been suggested that immunosurveillance primarily functions as a component of a more general process of cancer immunoediting.
== Tumor antigens ==
Tumors may express tumor antigens that are recognized by the immune system and may induce an immune response. These tumor antigens are either TSA (Tumor-specific antigen) or TAA (Tumor-associated antigen).
=== Tumor-specific ===
Tumor-specific antigens (TSA) are antigens that only occur in tumor cells. TSAs can be products of oncoviruses like E6 and E7 proteins of human papillomavirus, occurring in cervical carcinoma, or EBNA-1 protein of EBV, occurring in Burkitt's lymphoma cells. Another example of TSAs are abnormal products of mutated oncogenes (e.g. Ras protein) and anti-oncogenes (e.g. p53).
=== Tumor-associated antigens ===
Tumor-associated antigens (TAA) are present in healthy cells, but for some reason they also occur in tumor cells. However, they differ in quantity, place or time period of expression. Oncofetal antigens are tumor-associated antigens expressed by embryonic cells and by tumors. Examples of oncofetal antigens are AFP (α-fetoprotein), produced by hepatocellular carcinoma, or CEA (carcinoembryonic antigen), occurring in ovarian and colon cancer. More tumor-associated antigens are HER2/neu, EGFR or MAGE-1.
== Immunoediting ==
Cancer immunoediting is a process in which immune system interacts with tumor cells. It consists of three phases: elimination, equilibrium and escape. These phases are often referred to as "the three Es" of cancer immunoediting. Both adaptive and innate immune system participate in immunoediting.
In the elimination phase, the immune response leads to destruction of tumor cells and therefore to tumor suppression. However, some tumor cells may gain more mutations, change their characteristics and evade the immune system. These cells might enter the equilibrium phase, in which the immune system does not recognise all tumor cells, but at the same time the tumor does not grow. This condition may lead to the phase of escape, in which the tumor gains dominance over immune system, starts growing and establishes immunosuppressive environment.
As a consequence of immunoediting, tumor cell clones less responsive to the immune system gain dominance in the tumor through time, as the recognized cells are eliminated. This process may be considered akin to Darwinian evolution, where cells containing pro-oncogenic or immunosuppressive mutations survive to pass on their mutations to daughter cells, which may themselves mutate and undergo further selective pressure. This results in the tumor consisting of cells with decreased immunogenicity and can hardly be eliminated. This phenomenon was proven to happen as a result of immunotherapies of cancer patients.
== Tumor evasion mechanisms ==
CD8+ cytotoxic T cells are a fundamental element of anti-tumor immunity. Their TCR receptors recognise antigens presented by MHC class I and when bound, the Tc cell triggers its cytotoxic activity. MHC I are present on the surface of all nucleated cells. However, some cancer cells lower their MHC I expression and avoid being detected by the cytotoxic T cells. This can be done by mutation of MHC I gene or by lowering the sensitivity to IFN-γ (which influences the surface expression of MHC I). Tumor cells also have defects in antigen presentation pathway, what leads into down-regulation of tumor antigen presentations. Defects are for example in transporter associated with antigen processing (TAP) or tapasin. On the other hand, a complete loss of MHC I is a trigger for NK cells. Tumor cells therefore maintain a low expression of MHC I.
Another way to escape cytotoxic T cells is to stop expressing molecules essential for co-stimulation of cytotoxic T cells, such as CD80 or CD86.
Tumor cells express molecules to induce apoptosis or to inhibit T lymphocytes:
Expression of FasL on its surface, tumor cells may induce apoptosis of T lymphocytes by FasL-Fas interaction.
Expression of PD-L1 on the surface of tumor cells leads to suppression of T lymphocytes by PD1-PD-L1 interaction.
Tumor cells have gained resistance to effector mechanisms of NK and cytotoxic CD8+ T cell:
by loss of gene expression or inhibition of apoptotic signal pathway molecules: APAF1, Caspase 8, Bcl-2-associated X protein (bax) and Bcl-2 homologous antagonist killer (bak).
by induction of expression or overexpression of antiapoptotic molecules: Bcl-2, IAP or XIAP.
=== Tumor microenvironment ===
Production of TGF-β by tumor cells and other cells (such as myeloid-derived suppressor cell) leads to conversion of CD4+ T cell into suppressive regulatory T cell (Treg) by a contact dependent or independent stimulation. In a healthy tissue, functioning Tregs are essential to maintain self-tolerance. In a tumor, however, Tregs form an immunosuppressive microenvironment.
Tumor cells produce special cytokines (such as colony-stimulating factor) to produce myeloid-derived suppressor cell. These cells are heterogenous collection of cell types including precursors of dendritic cell, monocyte and neutrophil. MDSC have suppressive effects on T-lymphocytes, dendritic cells and macrophages. They produce immunosuppressive TGF-β and IL-10.
Another producer of suppressive TGF-β and IL-10 are tumor-associated macrophages, these macrophages have mostly phenotype of alternatively activated M2 macrophages. Their activation is promoted by TH type 2 cytokines (such as IL-4 and IL-13). Their main effects are immunosuppression, promotion of tumor growth and angiogenesis.
Tumor cells have non-classical MHC class I on their surface, for example HLA-G. HLA-G is inducer of Treg, MDSC, polarise macrophages into alternatively activated M2 and has other immunosuppressive effects on immune cells.
== Immunomodulation methods ==
Immune system is the key player in fighting cancer. As described above in mechanisms of tumor evasion, the tumor cells are modulating the immune response in their profit. It is possible to improve the immune response in order to boost the immunity against tumor cells.
monoclonal anti-CTLA4 and anti-PD-1 antibodies are called immune checkpoint inhibitors:
CTLA-4 is a receptor upregulated on the membrane of activated T lymphocytes, CTLA-4 CD80/86 interaction leads to switch off of T lymphocytes. By blocking this interaction with monoclonal anti CTLA-4 antibody we can increase the immune response. An example of approved drug is ipilimumab.
PD-1 is also an upregulated receptor on the surface of T lymphocytes after activation. Interaction PD-1 with PD-L1 leads to switching off or apoptosis. PD-L1 are molecules which can be produced by tumor cells. The monoclonal anti-PD-1 antibody is blocking this interaction thus leading to improvement of immune response in CD8+ T lymphocytes. An example of approved cancer drug is nivolumab.
Chimeric Antigen Receptor T cell
This CAR receptors are genetically engineered receptors with extracellular tumor specific binding sites and intracellular signalling domain that enables the T lymphocyte activation.
Cancer vaccine
Vaccine can be composed of killed tumor cells, recombinant tumor antigens, or dendritic cells incubated with tumor antigens (dendritic cell-based cancer vaccine)
== Relationship to chemotherapy ==
Obeid et al. investigated how inducing immunogenic cancer cell death ought to become a priority of cancer chemotherapy. He reasoned, the immune system would be able to play a factor via a 'bystander effect' in eradicating chemotherapy-resistant cancer cells. However, extensive research is still needed on how the immune response is triggered against dying tumour cells.
Professionals in the field have hypothesized that 'apoptotic cell death is poorly immunogenic whereas necrotic cell death is truly immunogenic'. This is perhaps because cancer cells being eradicated via a necrotic cell death pathway induce an immune response by triggering dendritic cells to mature, due to inflammatory response stimulation. On the other hand, apoptosis is connected to slight alterations within the plasma membrane causing the dying cells to be attractive to phagocytic cells. However, numerous animal studies have shown the superiority of vaccination with apoptotic cells, compared to necrotic cells, in eliciting anti-tumor immune responses.
Thus Obeid et al. propose that the way in which cancer cells die during chemotherapy is vital. Anthracyclins produce a beneficial immunogenic environment. The researchers report that when killing cancer cells with this agent uptake and presentation by antigen presenting dendritic cells is encouraged, thus allowing a T-cell response which can shrink tumours. Therefore, activating tumour-killing T-cells is crucial for immunotherapy success.
However, advanced cancer patients with immunosuppression have left researchers in a dilemma as to how to activate their T-cells. The way the host dendritic cells react and uptake tumour antigens to present to CD4+ and CD8+ T-cells is the key to success of the treatment.
== See also ==
Oncogenomics
== References == | Cancer immunology (immuno-oncology) is an interdisciplinary branch of biology and a sub-discipline of immunology that is concerned with understanding the role of the immune system in the progression and development of cancer; the most well known application is cancer immunotherapy, which utilises the immune system as a treatment for cancer. Cancer immunosurveillance and immunoediting are based on protection against development of tumors in animal systems and (ii) identification of targets for immune recognition of human cancer. | 1 |
366 | vidcon | VidCon (wikipedia) | VidCon is an annual convention for influencers, fans, executives, and online brands. The event primarily features prominent video stars from across the internet. It was founded by veteran YouTube creators John and Hank Green (Vlogbrothers), and was later acquired by Viacom (now Paramount) in 2018. Its offices remain in Missoula, Montana, sharing a building with Complexly. VidCon's international presence continues to expand with additional events planned in Singapore, Abu Dhabi, Mexico City, Australia, and São Paulo. In October 2020, VidCon Now relaunched as an ongoing, free digital offering.
== History ==
The first VidCon was held on July 9–11, 2010, at the Hyatt Regency Century Plaza hotel in Los Angeles and sold out in advance, with over 1,400 people attending.
In February 2018, Viacom (owner of the Viacom Media Networks and film studio Paramount Pictures) announced that they were acquiring VidCon, as part of its efforts to expand its live events business and expand from TV programming to next-generation entertainment platforms. Jim Louderback will remain the CEO of the convention, and co-founder Hank Green will continue to be involved and work closely with the team. Its offices will also exist in Missoula, Montana. Internet reception to this acquisition was mixed, with some noting the irony of Viacom acquiring VidCon a decade after their lawsuit against Google and YouTube for copyright infringement. Hank Green reassured fans that Viacom's acquisition would allow the convention to flourish. Three conferences were cancelled in 2020 due to the COVID-19 pandemic, and a series of online programming, VidCon Now, became available for registration.
In March 2021, VidCon announced that it would host its next U.S. conference at the Anaheim Convention Center from October 22–24, 2021, delayed from its usual summer scheduling in order to increase the chance that an in-person event could be held. VidCon also announced that TikTok would be the top sponsor of the 2021 event, replacing YouTube who had been the main sponsor since 2013. On August 20, however, VidCon announced the cancellation of its 2021 event "due to the recent increases in COVID-19 cases [in California] and evolving health and safety mandates." The convention was rescheduled to June 22–25, 2022 in Anaheim. The 2023 event was held between June 21–24 and was sponsored by YouTube for the first time since 2019.
== Attendance ==
== International conventions ==
== References ==
== External links ==
Media related to VidCon at Wikimedia Commons
Official website | VidCon is an annual convention for influencers, fans, executives, and online brands. The event primarily features prominent video stars from across the internet. It was founded by veteran YouTube creators John and Hank Green (Vlogbrothers), and was later acquired by Viacom (now Paramount) in 2018. Its offices remain in Missoula, Montana, sharing a building with Complexly. VidCon's international presence continues to expand with additional events planned in Singapore, Abu Dhabi, Mexico City, Australia, and São Paulo. In October 2020, VidCon Now relaunched as an ongoing, free digital offering.
| 5 |
367 | montgolfiere | Montgolfier brothers (wikipedia) | The Montgolfier brothers – Joseph-Michel Montgolfier (French pronunciation: [ʒozɛf miʃɛl mɔ̃ɡɔlfje]; 26 August 1740 – 26 June 1810) and Jacques-Étienne Montgolfier (French pronunciation: [ʒak etjɛn mɔ̃ɡɔlfje]; 6 January 1745 – 2 August 1799) – were aviation pioneers, balloonists and paper manufacturers from the commune Annonay in Ardèche, France. They invented the Montgolfière-style hot air balloon, globe aérostatique, which launched the first confirmed piloted ascent by humans in 1783, carrying Jacques-Étienne.
Joseph-Michel also invented the self-acting hydraulic ram (1796) and Jacques-Étienne founded the first paper-making vocational school. Together, the brothers invented a process to manufacture transparent paper.
== Early years ==
Joseph-Michel and Jacques-Étienne Montgolfier were born into a family of paper manufacturers. Their parents were Pierre Montgolfier (1700–1793) and Anne Duret (1701–1760), who had 16 children. Pierre Montgolfier established his eldest son, Raymond (1730–1772), as his successor.
Joseph-Michel was the 12th child. Described as a maverick and dreamer, he was impractical in terms of business and personal affairs. Étienne was the 15th child, had a much more even and businesslike temperament and was sent to Paris to train as an architect. After the sudden and unexpected death of Raymond in 1772, he was recalled to Annonay to run the family business. In the subsequent 10 years, Étienne applied his talent for technical innovation to the family business of paper making, which then as now was a high-tech industry. He succeeded in incorporating the latest Dutch innovations of the day into the family mills.
== Hot air balloon experiments, 1782–84 ==
=== Hot air balloon experiments, 1782 ===
Of the two brothers, it was Joseph who was first interested in aeronautics; as early as 1775 he built parachutes, and once jumped from the family house. He first contemplated building machines when he observed laundry drying over a fire incidentally form pockets that billowed upwards. Joseph made his first definitive experiments in November 1782 while living in Avignon. He reported some years later that he was watching a fire one evening while contemplating one of the great military issues of the day—an assault on the fortress of Gibraltar, which had proved impregnable from both sea and land. Joseph mused on the possibility of an air assault using troops lifted by the same force that was lifting the embers from the fire. He believed that the smoke itself was the buoyant part and contained within it a special gas, which he called "Montgolfier Gas", with a special property he called levity, which is why he preferred smoldering fuel.
Joseph then built a box-like chamber 0.9 by 0.9 by 1.2 metres (3 ft × 3 ft × 4 ft) out of very thin wood, and covered the sides and top with lightweight taffeta cloth. He crumpled and lit some paper under the bottom of the box. The contraption quickly lifted off its stand and collided with the ceiling.
Joseph recruited his brother to balloon building by writing, "Get in a supply of taffeta and of cordage, quickly, and you will see one of the most astonishing sights in the world." The two brothers built a similar device, three times larger having a volume 27 times greater. On 14 December 1782 they took their very first test flight, using ignited wool and hay as fuel. The lifting force was so great, that they lost control of their craft. The device floated nearly two kilometers (1.2 mi) but was destroyed after landing by the "indiscretion" of a bypasser.
=== Public demonstrations, summer 1783 ===
To make a public demonstration and to claim its invention the brothers constructed a globe-shaped balloon of sackcloth tightened with three thin layers of paper inside. The envelope could contain nearly 790 m3 (28,000 cu ft) of air and weighed 225 kg (496 lb). It was constructed of four pieces (the dome and three lateral bands) and held together by 1,800 buttons. A reinforcing fish net of cord covered the outside of the envelope.
On 4 June 1783, they flew the balloon at Annonay in front of a group of dignitaries from the états particuliers. The flight covered 2 km (1.2 mi), lasted 10 minutes, and had an estimated altitude of 1,600–2,000 m (5,200–6,600 ft). Word of their success quickly reached Paris. Étienne went to the capital to make further demonstrations and to solidify the brothers' claim to the invention of flight. Joseph, given his unkempt appearance and shyness, remained with the family. Étienne was the epitome of sober virtues ... modest in clothes and manner...
In collaboration with the wallpaper manufacturer Jean-Baptiste Réveillon, Étienne constructed a 37,500-cubic-foot (1,060 m3) envelope of taffeta coated with a varnish of alum for fireproofing. The balloon was sky blue and decorated with golden flourishes, signs of the zodiac, and suns. The design showed the intervention of Réveillon. The next test was on 11 September from the grounds of la Folie Titon, close to Réveillon's house. There was some concern about the effects of flight into the upper atmosphere on living creatures. The king proposed to launch two convicted criminals, but it is most likely that the inventors decided to send a sheep, a duck, and a rooster aloft first.
On 19 September 1783, the Aérostat Réveillon was flown with the first living beings in a basket attached to the balloon: a sheep called Montauciel ("Climb-to-the-sky"), a duck and a rooster. The sheep was believed to have a reasonable approximation of human physiology. The duck was expected to be unharmed by being lifted and was included as a control for effects created by the aircraft rather than the altitude. The rooster was included as a further control as it was a bird that did not fly at high altitudes. The demonstration was performed at the royal palace in Versailles, before King Louis XVI of France and Queen Marie Antoinette and a crowd. The flight lasted approximately eight minutes, covered two miles (3.2 km), and obtained an altitude of about 1,500 feet (460 m). The craft landed safely after flying.
=== Piloted flight, autumn 1783 ===
Since the animals survived, the king allowed flights with humans. Again in collaboration with Réveillon, Étienne built a 60,000-cubic-foot (1,700 m3) balloon for the purpose of making flights with humans. It was about 23 m (75 ft) tall and about 15 m (49 ft) in diameter. Réveillon supplied rich decorative touches of gold figures on a deep blue background, including fleur-de-lis, signs of the zodiac, and suns with Louis XVI's face in the center interlaced with the royal monogram in the central section. Red and blue drapery and golden eagles were at the base of the balloon. Étienne Montgolfier was the first human to lift off the Earth in a balloon, making a tethered test flight from the yard of the Réveillon workshop in the Faubourg Saint-Antoine, most likely on 15 October 1783. A little while later on that same day, physicist Pilâtre de Rozier became the second to ascend into the air, to an altitude of 80 feet (24 m), which was the length of the tether.
On 21 November 1783, the first free flight by humans was made by Pilâtre de Rozier, together with an army officer, the marquis d'Arlandes. The flight began from the grounds of the Château de la Muette close to the Bois de Boulogne park in the western outskirts of Paris. They flew about 3,000 feet (910 m) above Paris for a distance of nine kilometers. After 25 minutes, the balloon landed between the windmills, outside the city ramparts, on the Butte-aux-Cailles. Enough fuel remained on board at the end of the flight to have allowed the balloon to fly four to five times as far. However, burning embers from the fire were scorching the balloon fabric and had to be daubed out with sponges. As it appeared it could destroy the balloon, Pilâtre took off his coat to stop the fire.
The early flights made a sensation. During those first few years, numerous items, such as fans, furniture, handkerchiefs, pencil boxes, umbrella tops, etc., could be found with ballooning images engraved on them. Some items would be celebrating specific ballooning events, while others would be celebrating ballooning itself.
In December 1783, father Pierre Montgolfier was elevated to the nobility and the hereditary appellation of de Montgolfier by King Louis XVI of France.
=== Other balloons, competing claims ===
Some claim that the hot air balloon was invented about 74 years earlier by the Brazilian/Portuguese priest Bartolomeu de Gusmão. A description of his invention was published in 1709(?) in Vienna, and another one was found in the Vatican in about 1917.
However, this claim is not generally recognized by aviation historians outside the Portuguese-speaking community, in particular the Fédération Aéronautique Internationale.
On 1 December 1783, a few months after the Montgolfiers' first flight, Jacques Alexandre César Charles rose to an altitude of about 3 km (1.9 mi) near Paris in a hydrogen-filled balloon he had developed.
In early 1784, the Flesselles balloon, named after the unfortunate Jacques de Flesselles, later to be an early casualty at the Bastille, gave a rough landing to its passengers.
In June 1784, the Gustave (a hot air balloon christened La Gustave in honour of King Gustav III of Sweden's visit to Lyon) saw the first female aeronaut, Élisabeth Thible.
== Other Montgolfier inventions ==
Both brothers invented a process to manufacture transparent paper similar to vellum, imitating the technique of the English, followed by the papermakers Johannot and Réveillon.
In 1796, Joseph Michel Montgolfier invented the first self-acting hydraulic ram, a water pump to raise water for his paper mill at Voiron. In 1772, the British clockmaker John Whitehurst had invented its precursor, the "pulsation engine".
In 1797, Montgolfier's friend Matthew Boulton took out a British patent on his behalf.
In 1816, Joseph Michel's sons obtained a British patent for an improved version of the pump.
== Death, the Montgolfier company ==
Both brothers were freemasons in Les Neuf Soeurs lodge in Paris.
In 1799, Etienne de Montgolfier died on the way from Lyon to Annonay. His son-in-law, Barthélémy Barou de la Lombardière de Canson (1774–1859), succeeded him as the head of the company, thanks to his marriage with Alexandrine de Montgolfier. The company became Montgolfier et Canson in 1801, then Canson-Montgolfier in 1807. In 1810, Joseph-Michel died in Balaruc-les-Bains.
The Montgolfier Company in Annonay still exists under the name Canson. It produces fine art papers, school drawing papers and digital fine art and photography papers sold in 150 countries.
In 1983, the Montgolfier brothers were inducted into the International Air & Space Hall of Fame at the San Diego Air & Space Museum.
== See also ==
History of aviation
List of firsts in aviation
Wright brothers
== References ==
== External links ==
"Lighter than air: the Montgolfier brothers"
"Balloons and the Montgolfier brothers" | The Montgolfier brothers – Joseph-Michel Montgolfier (French pronunciation: [ʒozɛf miʃɛl mɔ̃ɡɔlfje]; 26 August 1740 – 26 June 1810) and Jacques-Étienne Montgolfier (French pronunciation: [ʒak etjɛn mɔ̃ɡɔlfje]; 6 January 1745 – 2 August 1799) – were aviation pioneers, balloonists and paper manufacturers from the commune Annonay in Ardèche, France. They invented the Montgolfière-style hot air balloon, globe aérostatique, which launched the first confirmed piloted ascent by humans in 1783, carrying Jacques-Étienne.
Joseph-Michel also invented the self-acting hydraulic ram (1796) and Jacques-Étienne founded the first paper-making vocational school. Together, the brothers invented a process to manufacture transparent paper. | 4 |
368 | jayhawk | Jayhawk (wiktionary) | From jayhawker. Re-imagined as a half-bluejay, half-sparrowhawk bird (one is the mascot of the University of Kansas).
Jayhawk
A native or inhabitant of the American state of Kansas.
Someone associated with the University of Kansas, for example as a student, alum, or sports team member, or as a fan.
Her career as a Jayhawk was marked by many achievements.
jayhawker | From jayhawker. Re-imagined as a half-bluejay, half-sparrowhawk bird (one is the mascot of the University of Kansas).
Jayhawk
A native or inhabitant of the American state of Kansas.
Someone associated with the University of Kansas, for example as a student, alum, or sports team member, or as a fan.
Her career as a Jayhawk was marked by many achievements.
jayhawker | 6 |
369 | jayhawk | jayhawk (wiktionary) | jayhawk (third-person singular simple present jayhawks, present participle jayhawking, simple past and past participle jayhawked)
(transitive, intransitive) To steal. | jayhawk (third-person singular simple present jayhawks, present participle jayhawking, simple past and past participle jayhawked)
(transitive, intransitive) To steal. | 1 |
370 | jayhawk | Jayhawk (wikipedia) | Jayhawk may refer to:
Jayhawker, originally a term for Free State or Union partisans during the Bleeding Kansas period and subsequently the United States Civil War, later applied generally to residents of Kansas
Jayhawk (mascot), the mascot of many schools and their sports teams, derived from the term Jayhawker
Kansas Jayhawks, teams of the University of Kansas
Head-Royce School, Oakland, California
Urbandale High School, Urbandale, Iowa
Jayhawk-Linn Junior-Senior High School near Mound City, Kansas
Vandercook Lake High School, Jackson, Michigan
Muskegon Community College, Muskegon, Michigan
Jamestown Community College, Jamestown, New York
Jefferson Central School, Jefferson, New York
Jericho High School in Jericho, New York
Jeannette City School District in Jeannette, Pennsylvania
St. Joseph Catholic High School (Ogden, Utah)
== Vehicles ==
Beechcraft AQM-37 Jayhawk, supersonic target drone produced by Raytheon for the US Navy
Raytheon T-1 Jayhawk, twin-engine jet trainer used by the US Air Force
Sikorsky MH-60 Jayhawk, US Coast Guard medium range recovery helicopter
== Other uses ==
Jayhawk, California, in El Dorado County
Jayhawk Owens (born 1969), American baseball player
The Jayhawks, a band from Minnesota
The Jayhawks (album), 1986
Jayhawk Area Council, an eastern Kansas council of the Boy Scouts of America
Tejas and Jayhawk, code names for canceled Intel microprocessors
Jayhawkers (film), a 2014 American sports drama/biographical film
== See also ==
All pages with titles containing Jayhawk
Kansas
University of Kansas | Jayhawk may refer to:
Jayhawker, originally a term for Free State or Union partisans during the Bleeding Kansas period and subsequently the United States Civil War, later applied generally to residents of Kansas
Jayhawk (mascot), the mascot of many schools and their sports teams, derived from the term Jayhawker
Kansas Jayhawks, teams of the University of Kansas
Head-Royce School, Oakland, California
Urbandale High School, Urbandale, Iowa
Jayhawk-Linn Junior-Senior High School near Mound City, Kansas
Vandercook Lake High School, Jackson, Michigan
Muskegon Community College, Muskegon, Michigan
Jamestown Community College, Jamestown, New York
Jefferson Central School, Jefferson, New York
Jericho High School in Jericho, New York
Jeannette City School District in Jeannette, Pennsylvania
St. Joseph Catholic High School (Ogden, Utah) | 11 |
371 | jayhawk | Jayhawker (wikipedia) | Jayhawker and red leg are terms that came to prominence in Kansas Territory during the Bleeding Kansas period of the 1850s; they were adopted by militant bands affiliated with the free-state cause during the American Civil War. These gangs were guerrillas who often clashed with pro-slavery groups from Missouri, known at the time in Kansas Territory as "Border Ruffians" or "Bushwhackers". After the Civil War, the word "Jayhawker" became synonymous with the people of Kansas, or anybody born in Kansas. Today a modified version of the term, Jayhawk, is used as a nickname for a native-born Kansan.
== Origin ==
=== Early usage ===
The term did not appear in the first American edition of Burtlett's Dictionary of Americanisms (1848), but was entered into the fourth improved and enlarged edition in 1877 as a cant name for a freebooting armed man in the western United States.
It was established that the term was adopted as a nickname by a group of emigrants from Illinois traveling to California in 1849, who got stuck in the Death Valley.
In 1858–59, the slang term "Jayhawking" became widely used as a synonym for stealing. Examples include:
O'ive been over till Eph. Kepley's a-jayhawking.
Men are now at Fort Scott, working by the day for a living as loyal as Gen. Blunt himself, who have had every hoof confiscated, or jayhawked, which is about the same thing, for all the benefit it is to the Government.
=== Missouri–Kansas border lexicon ===
The term became part of the lexicon of the Missouri–Kansas border in about 1858, during the Kansas territorial period. The term came to be used to describe militant bands nominally associated with the free-state cause. One early Kansas history contained this succinct characterization of the Jayhawkers: Confederated at first for defense against pro-slavery outrages, but ultimately falling more or less completely into the vocation of robbers and assassins, they have received the name—whatever its origin may be—of jayhawkers.
Farmer's Americanisms, old and new (1889) linked the term with anti-slavery advocates of late 1850s in Kansas.
G. Murlin Welch, a historian of the territorial period described the Jayhawkers as bands of men that were willing to fight, kill, and rob for a variety of motives that included defense against pro-slavery "Border Ruffians", abolition, driving pro-slavery settlers from their claims of land, revenge, and/or plunder and personal profit.
While the "Bleeding Kansas" era is generally regarded as beginning in 1856, the earliest documented uses of the term "jayhawker" during the Kansas troubles were in the late 1850s, after the issue of slavery in Kansas had essentially been decided in favor of the Free State cause. The earliest dated mention of the name comes from the autobiography of August Bondi, who came to Kansas in 1855. Bondi said he observed General James Lane addressing his forces as Jayhawkers in December 1857.
Another early reference to the term (as applied to the Kansas troubles) emerging at that time is provided in the retrospective account of Kansas newspaperman John McReynolds. McReynolds reportedly picked up the term from Pat Devlin, a Free State partisan described as "nothing more nor less than a dangerous bully." In mid-1858, McReynolds asked Devlin where he had acquired two fine horses that he had recently brought into the town of Osawatomie. Devlin replied that he "got them as the Jayhawk gets its birds in Ireland", which he explained as follows: "In Ireland a bird, which is called the Jayhawk, flies about after dark, seeking the roosts and nests of smaller birds, and not only robs nests of eggs, but frequently kills the birds." McReynolds understood Devlin had acquired his horses in the same manner the Jayhawk got its prey, and used the term in a Southern Kansas Herald newspaper column to describe a case of theft in the ongoing partisan violence. The term was quickly picked up by other newspapers, and "Jayhawkers" soon came to denote the militants and thieves affiliated with the Free State cause.
=== Kansas Union troops ===
The meaning of the jayhawker term evolved in the opening year of the American Civil War. When Charles Jennison, one of the territorial-era jayhawkers, was authorized to raise a regiment of cavalry to serve in the Union army, he characterized the unit as the "Independent Kansas Jay-Hawkers" on a recruiting poster. The regiment was officially termed the 7th Regiment Kansas Volunteer Cavalry, but was popularly known as Jennison's Jayhawkers. Thus, the term became associated with Union troops from Kansas. After the regiment was banished from the Missouri–Kansas border in the spring of 1862, it went on to participate in several battles including Union victories of the Battle of Iuka and the Second Battle of Corinth. Late in the war, the regiment returned to Kansas and contributed to Union victory in one of the last major battles in the Missouri–Kansas theater, the Battle of Mine Creek.
The Jayhawker term was applied not only to Jennison and his command, but to any Kansas troops engaged in punitive operations against the civilian population of western Missouri, in which the plundering and arson that characterized the territorial struggles were repeated, but on a much larger scale. For example, the term "Jayhawkers" also encompassed Senator Jim Lane and his Kansas Brigade, which sacked and burned Osceola, Missouri, in the opening months of the war after their defeat by Sterling Price's Missouri State Guard in the Battle of Dry Wood Creek.
=== Jayhawking in western Missouri ===
Jayhawking was a prominent aspect of Union military operations in western Missouri during the first year of the war. In addition to Osceola, the smaller Missouri towns of Morristown, Papinsvile, Butler, Dayton, and Columbus and large numbers of rural homes were also pillaged by Kansas troops led by James Lane, Charles R. Jennison, Daniel Read Anthony, and James Montgomery, among others. Scores if not hundreds of Missouri families were burned out of their homes in the middle of the winter of 1862.
Union Major General Henry Halleck on January 18, 1862 in a letter to General Lorenzo Thomas described Jennison's regiment as "no better than a band of robbers; they cross the line, rob, steal, plunder, and burn whatever they can lay their hands upon. They disgrace the name and uniform of American soldiers and are driving good Union men into the ranks of the secession army." There were no charges against Lane, Jennison, or other officers under Lane's command for their role in the jayhawking raids of 1861–1862, but Union General David H. Hunter succeeded in curtailing Lane's military role, and units of Kansas troops such as the 7th Regiment Kansas Volunteer Cavalry were shuffled off to other theaters of the war.
Further compounding confusion over what the term Jayhawker meant along the Missouri–Kansas border was its use in describing outright criminals like Marshall Cleveland, a captain of Jennison's Regiment, who resigned and turned to jayhawking. Cleveland operated under cover of supposed Unionism, but was outside the Union military command.
A newspaper reporter traveling through Kansas in 1863 provided definitions of jayhawker and associated terms: Jayhawkers, Red Legs, and Bushwhackers are everyday terms in Kansas and Western Missouri. A Jayhawker is a Unionist who professes to rob, burn out and murder only rebels in arms against the government. A Red Leg is a Jayhawker originally distinguished by the uniform of red leggings. A Red Leg, however, is regarded as more purely an indiscriminate thief and murderer than the Jayhawker or Bushwhacker. A Bushwhacker is a rebel Jayhawker, or a rebel who bands with others for the purpose of preying upon the lives and property of Union citizens. They are all lawless and indiscriminate in their iniquities.
=== Guerrilla fighting ===
The depredations of the Jayhawkers contributed to the descent of the Missouri–Kansas border region into some of the most vicious guerrilla fighting of the Civil War. In the first year of the war, much of the movable wealth in western Missouri had been transferred to Kansas, and large swaths of western Missouri had been laid waste, by an assortment of Kansas Jayhawkers ranging from outlaws and independent military bands to rogue federal troops such as Lane's Brigade and Jennison's Jayhawkers. In February 1862, the Union command instituted martial law due to "the crime of armed depredations or jay-hawking having reached a height dangerous to the peace and posterity to the whole State (Kansas) and seriously compromising the Union cause in the border counties of Missouri."
One expert on the Jayhawkers stated that the Border War would have been bad enough given the fighting between secessionist and unionist Missourians, "but it was basically Kansas craving for revenge and Kansas craving for loot that set the tone of the war. Nowhere else, with the grim exception of the East Kentucky and East Tennessee mountains, did the Civil War degenerate so completely into a squalid, murderous, slugging match as it did in Kansas and Missouri." The most infamous event in this war of raids and reprisals was Confederate leader William Quantrill's raid on Lawrence, Kansas, known as the Lawrence Massacre. In response to Quantrill's raid, the Union command issued General Order No. 11 (1863), the forced depopulation of specified Missouri border counties.
Intended to eliminate sanctuary and sustenance for pro-Confederate guerrilla fighters, it was enforced by troops from Kansas, and provided an excuse for a final round of plundering, arson, and summary execution perpetrated against the civilian population of western Missouri. In the words of one observer, "the Kansas–Missouri border was a disgrace even to barbarism."
=== Different meanings ===
As the war continued, the "Jayhawker" term came to be used by Confederates as a derogatory term for any troops from Kansas, but the term also had different meanings in different parts of the country. In Arkansas, the term was used by Confederate Arkansans as an epithet for any marauder, robber, or thief regardless of Union or Confederate affiliation. In Louisiana, the term was used to describe anti-Confederate guerrillas; in Texas, free-booting bands of draft dodgers and deserters.
Over time, proud of their state's contributions to the end of slavery and the preservation of the Union, Kansans embraced the "Jayhawker" term. The term came to be applied to people or items related to Kansas.
== Relationship to the University of Kansas Jayhawk ==
When the University of Kansas fielded their first football team in 1890, the team was called the Jayhawkers. Over time, the name was gradually supplanted by its shorter variant, and KU's sports teams are now exclusively known as the Kansas Jayhawks.
Historic descriptions of the ornithological origin of the "Jayhawker" term have varied. Writing on the troubles in Kansas Territory in 1859, one journalist stated the jayhawk was a hawk that preys on the jay. One of the "Jayhawkers of '49" recalled that the name sprang from their observation of hawks gracefully sailing in the air until "the audience of jays and other small but jealous and vicious birds sail in and jab him until he gets tired of show life and slides out of trouble in the lower earth." In the Pat Devlin stories, the jayhawk is described more in terms of its behavior (bullying, robbing, and killing) than the type of bird it is.
The link between the term "Jayhawkers" and any specific kind of bird, if such an association ever existed, had been lost or at least obscured by the time KU's bird mascot was invented in 1912, which was meant to serve as a visual representation of the Jayhawker movement, an homage by the university to the state's history. The originator of the bird mascot, Henry Maloy, struggled for over two years to create a pictorial symbol for the team, until hitting upon the bird idea. As explained by Maloy, "the term 'jayhawk' in the school yell was a verb and the term 'Jayhawkers' was the noun."
In 2011, the city of Osceola, Missouri produced a declaration condemning what city leadership viewed as a connection between the Jayhawk mascot and the historical Jayhawkers who burned the town in 1861.
In 2017, the Kansas football team unveiled uniforms with an American flag on the helmet, blue jerseys, and red pants which featured the words "Kansas Jay-Hawkers" above a seal featuring a sword and a rifle. Kansas Athletics stated that the red pants was an homage to the term "Redlegs," another name for Jayhawkers.
== Cultural influence ==
Plunderers and militant abolitionists were referred to as "Jayhawkers" or "Red Legs" and both were used as terms of derision towards those from Kansas after the Civil War. The term "Jayhawk" has evolved over the years to a term of pride used by some Kansans. The term "Red Leg" as applied to Kansans has disappeared from common lexicon.
Items stolen in raids into Missouri were frequently referred to as having been "Jayhawked."
The Jayhawkers are featured prominently in Lloyd Alexander's historical novel, "Border Hawk: August Bondi."
In the Gunsmoke radio show episode "Texas Cowboys" (1954 Radio), Jayhawkers follow a cattle drive and continue to stampede the herd. Marshal Matt Dillon allows the cowboys to "hurrah" Dodge. Jayhawkers were also the subject of the October 16, 1955 episode "Trouble in Kansas."
A cattle drive being held up by Jayhawkers is depicted in The Tall Men (1955).
In a 1959 Gunsmoke episode called "The Jayhawkers," men of that name try to extort money from cattle-drivers by threatening to scatter their herds unless paid off.
The movie The Jayhawkers! (1959) depicts a charismatic leader (Jeff Chandler) of a new independent Republic of Kansas in a showdown with an ex-renegade raider (Fess Parker), sent by the military governor to capture him and bring him to justice.
In a 1961 Rawhide episode called "Incident of the Phantom Bugler" a group referred to as Jayhawkers attempt to extort money from Gil Favor and crew to cross river.
Clint Eastwood's Missourian character in the film The Outlaw Josey Wales (1976) took up the Confederate cause after Redleg Jayhawkers from Kansas killed his son and raped and murdered his wife.
Jayhawker Colonel James Montgomery was portrayed as a racist, vengeful, and larcenous commander of a black regiment in the 1989 film Glory, where he is referred to as "a real Jayhawker from Kansas."
The 1999 movie Ride With the Devil, directed by Ang Lee, and starring Tobey Maguire, Skeet Ulrich, and Jewel depicts Jayhawkers raiding Missouri homesteads.
The 2014 movie Jayhawkers, directed by Oscar-winning filmmaker Kevin Willmott, follows the college career of Wilt Chamberlain and the 1956 Kansas Jayhawks basketball team.
An alternative country/alternative rock band originating in the 1980s from Minneapolis, Minnesota is named The Jayhawks.
An unincorporated community in El Dorado County, California is named Jayhawk, California.
The Wichita, Kansas wing of the Commemorative Air Force is known as the Jayhawk Wing.
The VII Corps of the United States Army official nickname was The Jayhawk Corps.
The United States Army Company A of the 9th aviation battalion of the 9th Infantry Division official nickname was The Jayhawks.
The United States Coast Guard operates the medium range twin engine helicopter HH-60 Jayhawk in the roles of maritime patrol, interdiction, and search and rescue.
The United States Navy operates the AQM-37 Jayhawk high speed target drone.
The United States Air Force and the Japan Air Self-Defense Force operate the advanced pilot trainer T-1 Jayhawk for students selected to fly strategic/tactical airlift or tanker aircraft.*The 184th Intel Wing call sign is the Fighting Jayhawks, and previously the Flying Jayhawks for many years before losing assigned aircraft.
== See also ==
Bushwhacker
Border Ruffian
Quantrill's Raiders
German Americans in the Civil War
Jayhawk
Jaywalking
William Sloan Tough
== References ==
== Further reading ==
Castel, Albert (1997). Civil War in Kansas: Reaping the Whirlwind. (ISBN 0-7006-0872-9)
Kerrihard, Bo. "America's Civil War: Missouri and Kansas." TheHistoryNet.
Starr, Steven Z. (1974). Jennison's Jayhawkers: A Civil War Cavalry Regiment and its Commander. (ISBN 0-8071-0218-0)
Wellman, Paul. (1962) A Dynasty of Western Outlaws (details the origins of the James-Younger and other outlaw gangs in the Kansas-Missouri border war).
== External links ==
Media related to Jayhawkers at Wikimedia Commons
"Jayhawker" . New International Encyclopedia. 1905.
"Jayhawker" . Encyclopedia Americana. 1920.
Pogo Comic Strip: The legendary comic strip "Pogo" considered the Kansas Jayhawk in this original art drawn by creator Walt Kelly, Kansas Historical Society | Jayhawker and red leg are terms that came to prominence in Kansas Territory during the Bleeding Kansas period of the 1850s; they were adopted by militant bands affiliated with the free-state cause during the American Civil War. These gangs were guerrillas who often clashed with pro-slavery groups from Missouri, known at the time in Kansas Territory as "Border Ruffians" or "Bushwhackers". After the Civil War, the word "Jayhawker" became synonymous with the people of Kansas, or anybody born in Kansas. Today a modified version of the term, Jayhawk, is used as a nickname for a native-born Kansan.
| 3 |
372 | uranium ammunition | Uranmunition (wiktionary) | From Uran + Munition.
Uranmunition f (genitive Uranmunition, plural Uranmunitionen)
(usually in the singular) depleted uranium ammunition
“Uranmunition” in Digitales Wörterbuch der deutschen Sprache
“Uranmunition” in Duden online
“Uranmunition” in Uni Leipzig: Wortschatz-Lexikon | From Uran + Munition.
Uranmunition f (genitive Uranmunition, plural Uranmunitionen)
(usually in the singular) depleted uranium ammunition
“Uranmunition” in Digitales Wörterbuch der deutschen Sprache
“Uranmunition” in Duden online
“Uranmunition” in Uni Leipzig: Wortschatz-Lexikon | 5 |
373 | feynmann diagram | Feynman diagram (wikipedia) | In theoretical physics, a Feynman diagram is a pictorial representation of the mathematical expressions describing the behavior and interaction of subatomic particles. The scheme is named after American physicist Richard Feynman, who introduced the diagrams in 1948. The interaction of subatomic particles can be complex and difficult to understand; Feynman diagrams give a simple visualization of what would otherwise be an arcane and abstract formula. According to David Kaiser, "Since the middle of the 20th century, theoretical physicists have increasingly turned to this tool to help them undertake critical calculations. Feynman diagrams have revolutionized nearly every aspect of theoretical physics." While the diagrams are applied primarily to quantum field theory, they can also be used in other areas of physics, such as solid-state theory. Frank Wilczek wrote that the calculations that won him the 2004 Nobel Prize in Physics "would have been literally unthinkable without Feynman diagrams, as would [Wilczek's] calculations that established a route to production and observation of the Higgs particle."
Feynman used Ernst Stueckelberg's interpretation of the positron as if it were an electron moving backward in time. Thus, antiparticles are represented as moving backward along the time axis in Feynman diagrams.
The calculation of probability amplitudes in theoretical particle physics requires the use of rather large and complicated integrals over a large number of variables. Feynman diagrams can represent these integrals graphically.
A Feynman diagram is a graphical representation of a perturbative contribution to the transition amplitude or correlation function of a quantum mechanical or statistical field theory. Within the canonical formulation of quantum field theory, a Feynman diagram represents a term in the Wick's expansion of the perturbative S-matrix. Alternatively, the path integral formulation of quantum field theory represents the transition amplitude as a weighted sum of all possible histories of the system from the initial to the final state, in terms of either particles or fields. The transition amplitude is then given as the matrix element of the S-matrix between the initial and final states of the quantum system.
== Motivation and history ==
When calculating scattering cross-sections in particle physics, the interaction between particles can be described by starting from a free field that describes the incoming and outgoing particles, and including an interaction Hamiltonian to describe how the particles deflect one another. The amplitude for scattering is the sum of each possible interaction history over all possible intermediate particle states. The number of times the interaction Hamiltonian acts is the order of the perturbation expansion, and the time-dependent perturbation theory for fields is known as the Dyson series. When the intermediate states at intermediate times are energy eigenstates (collections of particles with a definite momentum) the series is called old-fashioned perturbation theory (or time-dependent/time-ordered perturbation theory).
The Dyson series can be alternatively rewritten as a sum over Feynman diagrams, where at each vertex both the energy and momentum are conserved, but where the length of the energy-momentum four-vector is not necessarily equal to the mass, i.e. the intermediate particles are so-called off-shell. The Feynman diagrams are much easier to keep track of than "old-fashioned" terms, because the old-fashioned way treats the particle and antiparticle contributions as separate. Each Feynman diagram is the sum of exponentially many old-fashioned terms, because each internal line can separately represent either a particle or an antiparticle. In a non-relativistic theory, there are no antiparticles and there is no doubling, so each Feynman diagram includes only one term.
Feynman gave a prescription for calculating the amplitude (the Feynman rules, below) for any given diagram from a field theory Lagrangian. Each internal line corresponds to a factor of the virtual particle's propagator; each vertex where lines meet gives a factor derived from an interaction term in the Lagrangian, and incoming and outgoing lines carry an energy, momentum, and spin.
In addition to their value as a mathematical tool, Feynman diagrams provide deep physical insight into the nature of particle interactions. Particles interact in every way available; in fact, intermediate virtual particles are allowed to propagate faster than light. The probability of each final state is then obtained by summing over all such possibilities. This is closely tied to the functional integral formulation of quantum mechanics, also invented by Feynman—see path integral formulation.
The naïve application of such calculations often produces diagrams whose amplitudes are infinite, because the short-distance particle interactions require a careful limiting procedure, to include particle self-interactions. The technique of renormalization, suggested by Ernst Stueckelberg and Hans Bethe and implemented by Dyson, Feynman, Schwinger, and Tomonaga compensates for this effect and eliminates the troublesome infinities. After renormalization, calculations using Feynman diagrams match experimental results with very high accuracy.
Feynman diagram and path integral methods are also used in statistical mechanics and can even be applied to classical mechanics.
=== Alternative names ===
Murray Gell-Mann always referred to Feynman diagrams as Stueckelberg diagrams, after a Swiss physicist, Ernst Stueckelberg, who devised a similar notation many years earlier. Stueckelberg was motivated by the need for a manifestly covariant formalism for quantum field theory, but did not provide as automated a way to handle symmetry factors and loops, although he was first to find the correct physical interpretation in terms of forward and backward in time particle paths, all without the path-integral.
Historically, as a book-keeping device of covariant perturbation theory, the graphs were called Feynman–Dyson diagrams or Dyson graphs, because the path integral was unfamiliar when they were introduced, and Freeman Dyson's derivation from old-fashioned perturbation theory borrowed from the perturbative expansions in statistical mechanics was easier to follow for physicists trained in earlier methods. Feynman had to lobby hard for the diagrams, which confused the establishment physicists trained in equations and graphs.
== Representation of physical reality ==
In their presentations of fundamental interactions, written from the particle physics perspective, Gerard 't Hooft and Martinus Veltman gave good arguments for taking the original, non-regularized Feynman diagrams as the most succinct representation of our present knowledge about the physics of quantum scattering of fundamental particles. Their motivations are consistent with the convictions of James Daniel Bjorken and Sidney Drell:
The Feynman graphs and rules of calculation summarize quantum field theory in a form in close contact with the experimental numbers one wants to understand. Although the statement of the theory in terms of graphs may imply perturbation theory, use of graphical methods in the many-body problem shows that this formalism is flexible enough to deal with phenomena of nonperturbative characters ... Some modification of the Feynman rules of calculation may well outlive the elaborate mathematical structure of local canonical quantum field theory ...
In quantum field theories the Feynman diagrams are obtained from a Lagrangian by Feynman rules.
Dimensional regularization is a method for regularizing integrals in the evaluation of Feynman diagrams; it assigns values to them that are meromorphic functions of an auxiliary complex parameter d, called the dimension. Dimensional regularization writes a Feynman integral as an integral depending on the spacetime dimension d and spacetime points.
== Particle-path interpretation ==
A Feynman diagram is a representation of quantum field theory processes in terms of particle interactions. The particles are represented by the lines of the diagram, which can be squiggly or straight, with an arrow or without, depending on the type of particle. A point where lines connect to other lines is a vertex, and this is where the particles meet and interact: by emitting or absorbing new particles, deflecting one another, or changing type.
There are three different types of lines: internal lines connect two vertices, incoming lines extend from "the past" to a vertex and represent an initial state, and outgoing lines extend from a vertex to "the future" and represent the final state (the latter two are also known as external lines). Traditionally, the bottom of the diagram is the past and the top the future; other times, the past is to the left and the future to the right. When calculating correlation functions instead of scattering amplitudes, there is no past and future and all the lines are internal. The particles then begin and end on little x's, which represent the positions of the operators whose correlation is being calculated.
Feynman diagrams are a pictorial representation of a contribution to the total amplitude for a process that can happen in several different ways. When a group of incoming particles are to scatter off each other, the process can be thought of as one where the particles travel over all possible paths, including paths that go backward in time.
Feynman diagrams are often confused with spacetime diagrams and bubble chamber images because they all describe particle scattering. Feynman diagrams are graphs that represent the interaction of particles rather than the physical position of the particle during a scattering process. Unlike a bubble chamber picture, only the sum of all the Feynman diagrams represent any given particle interaction; particles do not choose a particular diagram each time they interact. The law of summation is in accord with the principle of superposition—every diagram contributes to the total amplitude for the process.
== Description ==
A Feynman diagram represents a perturbative contribution to the amplitude of a quantum transition from some initial quantum state to some final quantum state.
For example, in the process of electron-positron annihilation the initial state is one electron and one positron, the final state: two photons.
The initial state is often assumed to be at the left of the diagram and the final state at the right (although other conventions are also used quite often).
A Feynman diagram consists of points, called vertices, and lines attached to the vertices.
The particles in the initial state are depicted by lines sticking out in the direction of the initial state (e.g., to the left), the particles in the final state are represented by lines sticking out in the direction of the final state (e.g., to the right).
In QED there are two types of particles: matter particles such as electrons or positrons (called fermions) and exchange particles (called gauge bosons). They are represented in Feynman diagrams as follows:
Electron in the initial state is represented by a solid line, with an arrow indicating the spin of the particle e.g. pointing toward the vertex (→•).
Electron in the final state is represented by a line, with an arrow indicating the spin of the particle e.g. pointing away from the vertex: (•→).
Positron in the initial state is represented by a solid line, with an arrow indicating the spin of the particle e.g. pointing away from the vertex: (←•).
Positron in the final state is represented by a line, with an arrow indicating the spin of the particle e.g. pointing toward the vertex: (•←).
Virtual Photon in the initial and the final state is represented by a wavy line (~• and •~).
In QED a vertex always has three lines attached to it: one bosonic line, one fermionic line with arrow toward the vertex, and one fermionic line with arrow away from the vertex.
The vertices might be connected by a bosonic or fermionic propagator. A bosonic propagator is represented by a wavy line connecting two vertices (•~•). A fermionic propagator is represented by a solid line (with an arrow in one or another direction) connecting two vertices, (•←•).
The number of vertices gives the order of the term in the perturbation series expansion of the transition amplitude.
=== Electron–positron annihilation example ===
The electron–positron annihilation interaction:
e+ + e− → 2γ
has a contribution from the second order Feynman diagram shown adjacent:
In the initial state (at the bottom; early time) there is one electron (e−) and one positron (e+) and in the final state (at the top; late time) there are two photons (γ).
== Canonical quantization formulation ==
The probability amplitude for a transition of a quantum system (between asymptotically free states) from the initial state |i⟩ to the final state | f ⟩ is given by the matrix element
S
f
i
=
⟨
f
|
S
|
i
⟩
,
{\displaystyle S_{\rm {fi}}=\langle \mathrm {f} |S|\mathrm {i} \rangle \;,}
where S is the S-matrix. In terms of the time-evolution operator U, it is simply
S
=
lim
t
2
→
+
∞
lim
t
1
→
−
∞
U
(
t
2
,
t
1
)
.
{\displaystyle S=\lim _{t_{2}\rightarrow +\infty }\lim _{t_{1}\rightarrow -\infty }U(t_{2},t_{1})\;.}
In the interaction picture, this expands to
S
=
T
e
−
i
∫
−
∞
+
∞
d
τ
H
V
(
τ
)
.
{\displaystyle S={\mathcal {T}}e^{-i\int _{-\infty }^{+\infty }d\tau H_{V}(\tau )}.}
where HV is the interaction Hamiltonian and T signifies the time-ordered product of operators. Dyson's formula expands the time-ordered matrix exponential into a perturbation series in the powers of the interaction Hamiltonian density,
S
=
∑
n
=
0
∞
(
−
i
)
n
n
!
(
∏
j
=
1
n
∫
d
4
x
j
)
T
{
∏
j
=
1
n
H
V
(
x
j
)
}
≡
∑
n
=
0
∞
S
(
n
)
.
{\displaystyle S=\sum _{n=0}^{\infty }{\frac {(-i)^{n}}{n!}}\left(\prod _{j=1}^{n}\int d^{4}x_{j}\right){\mathcal {T}}\left\{\prod _{j=1}^{n}{\mathcal {H}}_{V}\left(x_{j}\right)\right\}\equiv \sum _{n=0}^{\infty }S^{(n)}\;.}
Equivalently, with the interaction Lagrangian LV, it is
S
=
∑
n
=
0
∞
i
n
n
!
(
∏
j
=
1
n
∫
d
4
x
j
)
T
{
∏
j
=
1
n
L
V
(
x
j
)
}
≡
∑
n
=
0
∞
S
(
n
)
.
{\displaystyle S=\sum _{n=0}^{\infty }{\frac {i^{n}}{n!}}\left(\prod _{j=1}^{n}\int d^{4}x_{j}\right){\mathcal {T}}\left\{\prod _{j=1}^{n}{\mathcal {L}}_{V}\left(x_{j}\right)\right\}\equiv \sum _{n=0}^{\infty }S^{(n)}\;.}
A Feynman diagram is a graphical representation of a single summand in the Wick's expansion of the time-ordered product in the nth-order term S(n) of the Dyson series of the S-matrix,
T
∏
j
=
1
n
L
V
(
x
j
)
=
∑
A
(
±
)
N
∏
j
=
1
n
L
V
(
x
j
)
,
{\displaystyle {\mathcal {T}}\prod _{j=1}^{n}{\mathcal {L}}_{V}\left(x_{j}\right)=\sum _{\text{A}}(\pm ){\mathcal {N}}\prod _{j=1}^{n}{\mathcal {L}}_{V}\left(x_{j}\right)\;,}
where N signifies the normal-ordered product of the operators and (±) takes care of the possible sign change when commuting the fermionic operators to bring them together for a contraction (a propagator) and A represents all possible contractions.
=== Feynman rules ===
The diagrams are drawn according to the Feynman rules, which depend upon the interaction Lagrangian. For the QED interaction Lagrangian
L
v
=
−
g
ψ
¯
γ
μ
ψ
A
μ
{\displaystyle L_{v}=-g{\bar {\psi }}\gamma ^{\mu }\psi A_{\mu }}
describing the interaction of a fermionic field ψ with a bosonic gauge field Aμ, the Feynman rules can be formulated in coordinate space as follows:
Each integration coordinate xj is represented by a point (sometimes called a vertex);
A bosonic propagator is represented by a wiggly line connecting two points;
A fermionic propagator is represented by a solid line connecting two points;
A bosonic field
A
μ
(
x
i
)
{\displaystyle A_{\mu }(x_{i})}
is represented by a wiggly line attached to the point xi;
A fermionic field ψ(xi) is represented by a solid line attached to the point xi with an arrow toward the point;
An anti-fermionic field ψ(xi) is represented by a solid line attached to the point xi with an arrow away from the point;
=== Example: second order processes in QED ===
The second order perturbation term in the S-matrix is
S
(
2
)
=
(
i
e
)
2
2
!
∫
d
4
x
d
4
x
′
T
ψ
¯
(
x
)
γ
μ
ψ
(
x
)
A
μ
(
x
)
ψ
¯
(
x
′
)
γ
ν
ψ
(
x
′
)
A
ν
(
x
′
)
.
{\displaystyle S^{(2)}={\frac {(ie)^{2}}{2!}}\int d^{4}x\,d^{4}x'\,T{\bar {\psi }}(x)\,\gamma ^{\mu }\,\psi (x)\,A_{\mu }(x)\,{\bar {\psi }}(x')\,\gamma ^{\nu }\,\psi (x')\,A_{\nu }(x').\;}
==== Scattering of fermions ====
The Wick's expansion of the integrand gives (among others) the following term
N
ψ
¯
(
x
)
γ
μ
ψ
(
x
)
ψ
¯
(
x
′
)
γ
ν
ψ
(
x
′
)
A
μ
(
x
)
A
ν
(
x
′
)
_
,
{\displaystyle N{\bar {\psi }}(x)\gamma ^{\mu }\psi (x){\bar {\psi }}(x')\gamma ^{\nu }\psi (x'){\underline {A_{\mu }(x)A_{\nu }(x')}}\;,}
where
A
μ
(
x
)
A
ν
(
x
′
)
_
=
∫
d
4
k
(
2
π
)
4
−
i
g
μ
ν
k
2
+
i
0
e
−
i
k
(
x
−
x
′
)
{\displaystyle {\underline {A_{\mu }(x)A_{\nu }(x')}}=\int {\frac {d^{4}k}{(2\pi )^{4}}}{\frac {-ig_{\mu \nu }}{k^{2}+i0}}e^{-ik(x-x')}}
is the electromagnetic contraction (propagator) in the Feynman gauge. This term is represented by the Feynman diagram at the right. This diagram gives contributions to the following processes:
e− e− scattering (initial state at the right, final state at the left of the diagram);
e+ e+ scattering (initial state at the left, final state at the right of the diagram);
e− e+ scattering (initial state at the bottom/top, final state at the top/bottom of the diagram).
==== Compton scattering and annihilation/generation of e− e+ pairs ====
Another interesting term in the expansion is
N
ψ
¯
(
x
)
γ
μ
ψ
(
x
)
ψ
¯
(
x
′
)
_
γ
ν
ψ
(
x
′
)
A
μ
(
x
)
A
ν
(
x
′
)
,
{\displaystyle N{\bar {\psi }}(x)\,\gamma ^{\mu }\,{\underline {\psi (x)\,{\bar {\psi }}(x')}}\,\gamma ^{\nu }\,\psi (x')\,A_{\mu }(x)\,A_{\nu }(x')\;,}
where
ψ
(
x
)
ψ
¯
(
x
′
)
_
=
∫
d
4
p
(
2
π
)
4
i
γ
p
−
m
+
i
0
e
−
i
p
(
x
−
x
′
)
{\displaystyle {\underline {\psi (x){\bar {\psi }}(x')}}=\int {\frac {d^{4}p}{(2\pi )^{4}}}{\frac {i}{\gamma p-m+i0}}e^{-ip(x-x')}}
is the fermionic contraction (propagator).
== Path integral formulation ==
In a path integral, the field Lagrangian, integrated over all possible field histories, defines the probability amplitude to go from one field configuration to another. In order to make sense, the field theory should have a well-defined ground state, and the integral should be performed a little bit rotated into imaginary time, i.e. a Wick rotation. The path integral formalism is completely equivalent to the canonical operator formalism above.
=== Scalar field Lagrangian ===
A simple example is the free relativistic scalar field in d dimensions, whose action integral is:
S
=
∫
1
2
∂
μ
ϕ
∂
μ
ϕ
d
d
x
.
{\displaystyle S=\int {\tfrac {1}{2}}\partial _{\mu }\phi \partial ^{\mu }\phi \,d^{d}x\,.}
The probability amplitude for a process is:
∫
A
B
e
i
S
D
ϕ
,
{\displaystyle \int _{A}^{B}e^{iS}\,D\phi \,,}
where A and B are space-like hypersurfaces that define the boundary conditions. The collection of all the φ(A) on the starting hypersurface give the initial value of the field, analogous to the starting position for a point particle, and the field values φ(B) at each point of the final hypersurface defines the final field value, which is allowed to vary, giving a different amplitude to end up at different values. This is the field-to-field transition amplitude.
The path integral gives the expectation value of operators between the initial and final state:
∫
A
B
e
i
S
ϕ
(
x
1
)
⋯
ϕ
(
x
n
)
D
ϕ
=
⟨
A
|
ϕ
(
x
1
)
⋯
ϕ
(
x
n
)
|
B
⟩
,
{\displaystyle \int _{A}^{B}e^{iS}\phi (x_{1})\cdots \phi (x_{n})\,D\phi =\left\langle A\left|\phi (x_{1})\cdots \phi (x_{n})\right|B\right\rangle \,,}
and in the limit that A and B recede to the infinite past and the infinite future, the only contribution that matters is from the ground state (this is only rigorously true if the path-integral is defined slightly rotated into imaginary time). The path integral can be thought of as analogous to a probability distribution, and it is convenient to define it so that multiplying by a constant does not change anything:
∫
e
i
S
ϕ
(
x
1
)
⋯
ϕ
(
x
n
)
D
ϕ
∫
e
i
S
D
ϕ
=
⟨
0
|
ϕ
(
x
1
)
⋯
ϕ
(
x
n
)
|
0
⟩
.
{\displaystyle {\frac {\displaystyle \int e^{iS}\phi (x_{1})\cdots \phi (x_{n})\,D\phi }{\displaystyle \int e^{iS}\,D\phi }}=\left\langle 0\left|\phi (x_{1})\cdots \phi (x_{n})\right|0\right\rangle \,.}
The normalization factor on the bottom is called the partition function for the field, and it coincides with the statistical mechanical partition function at zero temperature when rotated into imaginary time.
The initial-to-final amplitudes are ill-defined if one thinks of the continuum limit right from the beginning, because the fluctuations in the field can become unbounded. So the path-integral can be thought of as on a discrete square lattice, with lattice spacing a and the limit a → 0 should be taken carefully. If the final results do not depend on the shape of the lattice or the value of a, then the continuum limit exists.
=== On a lattice ===
On a lattice, (i), the field can be expanded in Fourier modes:
ϕ
(
x
)
=
∫
d
k
(
2
π
)
d
ϕ
(
k
)
e
i
k
⋅
x
=
∫
k
ϕ
(
k
)
e
i
k
x
.
{\displaystyle \phi (x)=\int {\frac {dk}{(2\pi )^{d}}}\phi (k)e^{ik\cdot x}=\int _{k}\phi (k)e^{ikx}\,.}
Here the integration domain is over k restricted to a cube of side length 2π/a, so that large values of k are not allowed. It is important to note that the k-measure contains the factors of 2π from Fourier transforms, this is the best standard convention for k-integrals in QFT. The lattice means that fluctuations at large k are not allowed to contribute right away, they only start to contribute in the limit a → 0. Sometimes, instead of a lattice, the field modes are just cut off at high values of k instead.
It is also convenient from time to time to consider the space-time volume to be finite, so that the k modes are also a lattice. This is not strictly as necessary as the space-lattice limit, because interactions in k are not localized, but it is convenient for keeping track of the factors in front of the k-integrals and the momentum-conserving delta functions that will arise.
On a lattice, (ii), the action needs to be discretized:
S
=
∑
⟨
x
,
y
⟩
1
2
(
ϕ
(
x
)
−
ϕ
(
y
)
)
2
,
{\displaystyle S=\sum _{\langle x,y\rangle }{\tfrac {1}{2}}{\big (}\phi (x)-\phi (y){\big )}^{2}\,,}
where ⟨x,y⟩ is a pair of nearest lattice neighbors x and y. The discretization should be thought of as defining what the derivative ∂μφ means.
In terms of the lattice Fourier modes, the action can be written:
S
=
∫
k
(
(
1
−
cos
(
k
1
)
)
+
(
1
−
cos
(
k
2
)
)
+
⋯
+
(
1
−
cos
(
k
d
)
)
)
ϕ
k
∗
ϕ
k
.
{\displaystyle S=\int _{k}{\Big (}{\big (}1-\cos(k_{1}){\big )}+{\big (}1-\cos(k_{2}){\big )}+\cdots +{\big (}1-\cos(k_{d}){\big )}{\Big )}\phi _{k}^{*}\phi ^{k}\,.}
For k near zero this is:
S
=
∫
k
1
2
k
2
|
ϕ
(
k
)
|
2
.
{\displaystyle S=\int _{k}{\tfrac {1}{2}}k^{2}\left|\phi (k)\right|^{2}\,.}
Now we have the continuum Fourier transform of the original action. In finite volume, the quantity ddk is not infinitesimal, but becomes the volume of a box made by neighboring Fourier modes, or (2π/V)d .
The field φ is real-valued, so the Fourier transform obeys:
ϕ
(
k
)
∗
=
ϕ
(
−
k
)
.
{\displaystyle \phi (k)^{*}=\phi (-k)\,.}
In terms of real and imaginary parts, the real part of φ(k) is an even function of k, while the imaginary part is odd. The Fourier transform avoids double-counting, so that it can be written:
S
=
∫
k
1
2
k
2
ϕ
(
k
)
ϕ
(
−
k
)
{\displaystyle S=\int _{k}{\tfrac {1}{2}}k^{2}\phi (k)\phi (-k)}
over an integration domain that integrates over each pair (k,−k) exactly once.
For a complex scalar field with action
S
=
∫
1
2
∂
μ
ϕ
∗
∂
μ
ϕ
d
d
x
{\displaystyle S=\int {\tfrac {1}{2}}\partial _{\mu }\phi ^{*}\partial ^{\mu }\phi \,d^{d}x}
the Fourier transform is unconstrained:
S
=
∫
k
1
2
k
2
|
ϕ
(
k
)
|
2
{\displaystyle S=\int _{k}{\tfrac {1}{2}}k^{2}\left|\phi (k)\right|^{2}}
and the integral is over all k.
Integrating over all different values of φ(x) is equivalent to integrating over all Fourier modes, because taking a Fourier transform is a unitary linear transformation of field coordinates. When you change coordinates in a multidimensional integral by a linear transformation, the value of the new integral is given by the determinant of the transformation matrix. If
y
i
=
A
i
j
x
j
,
{\displaystyle y_{i}=A_{ij}x_{j}\,,}
then
det
(
A
)
∫
d
x
1
d
x
2
⋯
d
x
n
=
∫
d
y
1
d
y
2
⋯
d
y
n
.
{\displaystyle \det(A)\int dx_{1}\,dx_{2}\cdots \,dx_{n}=\int dy_{1}\,dy_{2}\cdots \,dy_{n}\,.}
If A is a rotation, then
A
T
A
=
I
{\displaystyle A^{\mathrm {T} }A=I}
so that det A = ±1, and the sign depends on whether the rotation includes a reflection or not.
The matrix that changes coordinates from φ(x) to φ(k) can be read off from the definition of a Fourier transform.
A
k
x
=
e
i
k
x
{\displaystyle A_{kx}=e^{ikx}\,}
and the Fourier inversion theorem tells you the inverse:
A
k
x
−
1
=
e
−
i
k
x
{\displaystyle A_{kx}^{-1}=e^{-ikx}\,}
which is the complex conjugate-transpose, up to factors of 2π. On a finite volume lattice, the determinant is nonzero and independent of the field values.
det
A
=
1
{\displaystyle \det A=1\,}
and the path integral is a separate factor at each value of k.
∫
exp
(
i
2
∑
k
k
2
ϕ
∗
(
k
)
ϕ
(
k
)
)
D
ϕ
=
∏
k
∫
ϕ
k
e
i
2
k
2
|
ϕ
k
|
2
d
d
k
{\displaystyle \int \exp \left({\frac {i}{2}}\sum _{k}k^{2}\phi ^{*}(k)\phi (k)\right)\,D\phi =\prod _{k}\int _{\phi _{k}}e^{{\frac {i}{2}}k^{2}\left|\phi _{k}\right|^{2}\,d^{d}k}\,}
The factor ddk is the infinitesimal volume of a discrete cell in k-space, in a square lattice box
d
d
k
=
(
1
L
)
d
,
{\displaystyle d^{d}k=\left({\frac {1}{L}}\right)^{d}\,,}
where L is the side-length of the box. Each separate factor is an oscillatory Gaussian, and the width of the Gaussian diverges as the volume goes to infinity.
In imaginary time, the Euclidean action becomes positive definite, and can be interpreted as a probability distribution. The probability of a field having values φk is
e
∫
k
−
1
2
k
2
ϕ
k
∗
ϕ
k
=
∏
k
e
−
k
2
|
ϕ
k
|
2
d
d
k
.
{\displaystyle e^{\int _{k}-{\tfrac {1}{2}}k^{2}\phi _{k}^{*}\phi _{k}}=\prod _{k}e^{-k^{2}\left|\phi _{k}\right|^{2}\,d^{d}k}\,.}
The expectation value of the field is the statistical expectation value of the field when chosen according to the probability distribution:
⟨
ϕ
(
x
1
)
⋯
ϕ
(
x
n
)
⟩
=
∫
e
−
S
ϕ
(
x
1
)
⋯
ϕ
(
x
n
)
D
ϕ
∫
e
−
S
D
ϕ
{\displaystyle \left\langle \phi (x_{1})\cdots \phi (x_{n})\right\rangle ={\frac {\displaystyle \int e^{-S}\phi (x_{1})\cdots \phi (x_{n})\,D\phi }{\displaystyle \int e^{-S}\,D\phi }}}
Since the probability of φk is a product, the value of φk at each separate value of k is independently Gaussian distributed. The variance of the Gaussian is 1/k2ddk, which is formally infinite, but that just means that the fluctuations are unbounded in infinite volume. In any finite volume, the integral is replaced by a discrete sum, and the variance of the integral is V/k2.
=== Monte Carlo ===
The path integral defines a probabilistic algorithm to generate a Euclidean scalar field configuration. Randomly pick the real and imaginary parts of each Fourier mode at wavenumber k to be a Gaussian random variable with variance 1/k2. This generates a configuration φC(k) at random, and the Fourier transform gives φC(x). For real scalar fields, the algorithm must generate only one of each pair φ(k), φ(−k), and make the second the complex conjugate of the first.
To find any correlation function, generate a field again and again by this procedure, and find the statistical average:
⟨
ϕ
(
x
1
)
⋯
ϕ
(
x
n
)
⟩
=
lim
|
C
|
→
∞
∑
C
ϕ
C
(
x
1
)
⋯
ϕ
C
(
x
n
)
|
C
|
{\displaystyle \left\langle \phi (x_{1})\cdots \phi (x_{n})\right\rangle =\lim _{|C|\rightarrow \infty }{\frac {\displaystyle \sum _{C}\phi _{C}(x_{1})\cdots \phi _{C}(x_{n})}{|C|}}}
where |C| is the number of configurations, and the sum is of the product of the field values on each configuration. The Euclidean correlation function is just the same as the correlation function in statistics or statistical mechanics. The quantum mechanical correlation functions are an analytic continuation of the Euclidean correlation functions.
For free fields with a quadratic action, the probability distribution is a high-dimensional Gaussian, and the statistical average is given by an explicit formula. But the Monte Carlo method also works well for bosonic interacting field theories where there is no closed form for the correlation functions.
=== Scalar propagator ===
Each mode is independently Gaussian distributed. The expectation of field modes is easy to calculate:
⟨
ϕ
k
ϕ
k
′
⟩
=
0
{\displaystyle \left\langle \phi _{k}\phi _{k'}\right\rangle =0\,}
for k ≠ k′, since then the two Gaussian random variables are independent and both have zero mean.
⟨
ϕ
k
ϕ
k
⟩
=
V
k
2
{\displaystyle \left\langle \phi _{k}\phi _{k}\right\rangle ={\frac {V}{k^{2}}}}
in finite volume V, when the two k-values coincide, since this is the variance of the Gaussian. In the infinite volume limit,
⟨
ϕ
(
k
)
ϕ
(
k
′
)
⟩
=
δ
(
k
−
k
′
)
1
k
2
{\displaystyle \left\langle \phi (k)\phi (k')\right\rangle =\delta (k-k'){\frac {1}{k^{2}}}}
Strictly speaking, this is an approximation: the lattice propagator is:
⟨
ϕ
(
k
)
ϕ
(
k
′
)
⟩
=
δ
(
k
−
k
′
)
1
2
(
d
−
cos
(
k
1
)
+
cos
(
k
2
)
⋯
+
cos
(
k
d
)
)
{\displaystyle \left\langle \phi (k)\phi (k')\right\rangle =\delta (k-k'){\frac {1}{2{\big (}d-\cos(k_{1})+\cos(k_{2})\cdots +\cos(k_{d}){\big )}}}}
But near k = 0, for field fluctuations long compared to the lattice spacing, the two forms coincide.
It is important to emphasize that the delta functions contain factors of 2π, so that they cancel out the 2π factors in the measure for k integrals.
δ
(
k
)
=
(
2
π
)
d
δ
D
(
k
1
)
δ
D
(
k
2
)
⋯
δ
D
(
k
d
)
{\displaystyle \delta (k)=(2\pi )^{d}\delta _{D}(k_{1})\delta _{D}(k_{2})\cdots \delta _{D}(k_{d})\,}
where δD(k) is the ordinary one-dimensional Dirac delta function. This convention for delta-functions is not universal—some authors keep the factors of 2π in the delta functions (and in the k-integration) explicit.
=== Equation of motion ===
The form of the propagator can be more easily found by using the equation of motion for the field. From the Lagrangian, the equation of motion is:
∂
μ
∂
μ
ϕ
=
0
{\displaystyle \partial _{\mu }\partial ^{\mu }\phi =0\,}
and in an expectation value, this says:
∂
μ
∂
μ
⟨
ϕ
(
x
)
ϕ
(
y
)
⟩
=
0
{\displaystyle \partial _{\mu }\partial ^{\mu }\left\langle \phi (x)\phi (y)\right\rangle =0}
Where the derivatives act on x, and the identity is true everywhere except when x and y coincide, and the operator order matters. The form of the singularity can be understood from the canonical commutation relations to be a delta-function. Defining the (Euclidean) Feynman propagator Δ as the Fourier transform of the time-ordered two-point function (the one that comes from the path-integral):
∂
2
Δ
(
x
)
=
i
δ
(
x
)
{\displaystyle \partial ^{2}\Delta (x)=i\delta (x)\,}
So that:
Δ
(
k
)
=
i
k
2
{\displaystyle \Delta (k)={\frac {i}{k^{2}}}}
If the equations of motion are linear, the propagator will always be the reciprocal of the quadratic-form matrix that defines the free Lagrangian, since this gives the equations of motion. This is also easy to see directly from the path integral. The factor of i disappears in the Euclidean theory.
==== Wick theorem ====
Because each field mode is an independent Gaussian, the expectation values for the product of many field modes obeys Wick's theorem:
⟨
ϕ
(
k
1
)
ϕ
(
k
2
)
⋯
ϕ
(
k
n
)
⟩
{\displaystyle \left\langle \phi (k_{1})\phi (k_{2})\cdots \phi (k_{n})\right\rangle }
is zero unless the field modes coincide in pairs. This means that it is zero for an odd number of φ, and for an even number of φ, it is equal to a contribution from each pair separately, with a delta function.
⟨
ϕ
(
k
1
)
⋯
ϕ
(
k
2
n
)
⟩
=
∑
∏
i
,
j
δ
(
k
i
−
k
j
)
k
i
2
{\displaystyle \left\langle \phi (k_{1})\cdots \phi (k_{2n})\right\rangle =\sum \prod _{i,j}{\frac {\delta \left(k_{i}-k_{j}\right)}{k_{i}^{2}}}}
where the sum is over each partition of the field modes into pairs, and the product is over the pairs. For example,
⟨
ϕ
(
k
1
)
ϕ
(
k
2
)
ϕ
(
k
3
)
ϕ
(
k
4
)
⟩
=
δ
(
k
1
−
k
2
)
k
1
2
δ
(
k
3
−
k
4
)
k
3
2
+
δ
(
k
1
−
k
3
)
k
3
2
δ
(
k
2
−
k
4
)
k
2
2
+
δ
(
k
1
−
k
4
)
k
1
2
δ
(
k
2
−
k
3
)
k
2
2
{\displaystyle \left\langle \phi (k_{1})\phi (k_{2})\phi (k_{3})\phi (k_{4})\right\rangle ={\frac {\delta (k_{1}-k_{2})}{k_{1}^{2}}}{\frac {\delta (k_{3}-k_{4})}{k_{3}^{2}}}+{\frac {\delta (k_{1}-k_{3})}{k_{3}^{2}}}{\frac {\delta (k_{2}-k_{4})}{k_{2}^{2}}}+{\frac {\delta (k_{1}-k_{4})}{k_{1}^{2}}}{\frac {\delta (k_{2}-k_{3})}{k_{2}^{2}}}}
An interpretation of Wick's theorem is that each field insertion can be thought of as a dangling line, and the expectation value is calculated by linking up the lines in pairs, putting a delta function factor that ensures that the momentum of each partner in the pair is equal, and dividing by the propagator.
==== Higher Gaussian moments — completing Wick's theorem ====
There is a subtle point left before Wick's theorem is proved—what if more than two of the
ϕ
{\displaystyle \phi }
s have the same momentum? If it's an odd number, the integral is zero; negative values cancel with the positive values. But if the number is even, the integral is positive. The previous demonstration assumed that the
ϕ
{\displaystyle \phi }
s would only match up in pairs.
But the theorem is correct even when arbitrarily many of the
ϕ
{\displaystyle \phi }
are equal, and this is a notable property of Gaussian integration:
I
=
∫
e
−
a
x
2
/
2
d
x
=
2
π
a
{\displaystyle I=\int e^{-ax^{2}/2}dx={\sqrt {\frac {2\pi }{a}}}}
∂
n
∂
a
n
I
=
∫
x
2
n
2
n
e
−
a
x
2
/
2
d
x
=
1
⋅
3
⋅
5
…
⋅
(
2
n
−
1
)
2
⋅
2
⋅
2
…
⋅
2
2
π
a
−
2
n
+
1
2
{\displaystyle {\frac {\partial ^{n}}{\partial a^{n}}}I=\int {\frac {x^{2n}}{2^{n}}}e^{-ax^{2}/2}dx={\frac {1\cdot 3\cdot 5\ldots \cdot (2n-1)}{2\cdot 2\cdot 2\ldots \;\;\;\;\;\cdot 2\;\;\;\;\;\;}}{\sqrt {2\pi }}\,a^{-{\frac {2n+1}{2}}}}
Dividing by I,
⟨
x
2
n
⟩
=
∫
x
2
n
e
−
a
x
2
/
2
∫
e
−
a
x
2
/
2
=
1
⋅
3
⋅
5
…
⋅
(
2
n
−
1
)
1
a
n
{\displaystyle \left\langle x^{2n}\right\rangle ={\frac {\displaystyle \int x^{2n}e^{-ax^{2}/2}}{\displaystyle \int e^{-ax^{2}/2}}}=1\cdot 3\cdot 5\ldots \cdot (2n-1){\frac {1}{a^{n}}}}
⟨
x
2
⟩
=
1
a
{\displaystyle \left\langle x^{2}\right\rangle ={\frac {1}{a}}}
If Wick's theorem were correct, the higher moments would be given by all possible pairings of a list of 2n different x:
⟨
x
1
x
2
x
3
⋯
x
2
n
⟩
{\displaystyle \left\langle x_{1}x_{2}x_{3}\cdots x_{2n}\right\rangle }
where the x are all the same variable, the index is just to keep track of the number of ways to pair them. The first x can be paired with 2n − 1 others, leaving 2n − 2. The next unpaired x can be paired with 2n − 3 different x leaving 2n − 4, and so on. This means that Wick's theorem, uncorrected, says that the expectation value of x2n should be:
⟨
x
2
n
⟩
=
(
2
n
−
1
)
⋅
(
2
n
−
3
)
…
⋅
5
⋅
3
⋅
1
⟨
x
2
⟩
n
{\displaystyle \left\langle x^{2n}\right\rangle =(2n-1)\cdot (2n-3)\ldots \cdot 5\cdot 3\cdot 1\left\langle x^{2}\right\rangle ^{n}}
and this is in fact the correct answer. So Wick's theorem holds no matter how many of the momenta of the internal variables coincide.
==== Interaction ====
Interactions are represented by higher order contributions, since quadratic contributions are always Gaussian. The simplest interaction is the quartic self-interaction, with an action:
S
=
∫
∂
μ
ϕ
∂
μ
ϕ
+
λ
4
!
ϕ
4
.
{\displaystyle S=\int \partial ^{\mu }\phi \partial _{\mu }\phi +{\frac {\lambda }{4!}}\phi ^{4}.}
The reason for the combinatorial factor 4! will be clear soon. Writing the action in terms of the lattice (or continuum) Fourier modes:
S
=
∫
k
k
2
|
ϕ
(
k
)
|
2
+
λ
4
!
∫
k
1
k
2
k
3
k
4
ϕ
(
k
1
)
ϕ
(
k
2
)
ϕ
(
k
3
)
ϕ
(
k
4
)
δ
(
k
1
+
k
2
+
k
3
+
k
4
)
=
S
F
+
X
.
{\displaystyle S=\int _{k}k^{2}\left|\phi (k)\right|^{2}+{\frac {\lambda }{4!}}\int _{k_{1}k_{2}k_{3}k_{4}}\phi (k_{1})\phi (k_{2})\phi (k_{3})\phi (k_{4})\delta (k_{1}+k_{2}+k_{3}+k_{4})=S_{F}+X.}
Where SF is the free action, whose correlation functions are given by Wick's theorem. The exponential of S in the path integral can be expanded in powers of λ, giving a series of corrections to the free action.
e
−
S
=
e
−
S
F
(
1
+
X
+
1
2
!
X
X
+
1
3
!
X
X
X
+
⋯
)
{\displaystyle e^{-S}=e^{-S_{F}}\left(1+X+{\frac {1}{2!}}XX+{\frac {1}{3!}}XXX+\cdots \right)}
The path integral for the interacting action is then a power series of corrections to the free action. The term represented by X should be thought of as four half-lines, one for each factor of φ(k). The half-lines meet at a vertex, which contributes a delta-function that ensures that the sum of the momenta are all equal.
To compute a correlation function in the interacting theory, there is a contribution from the X terms now. For example, the path-integral for the four-field correlator:
⟨
ϕ
(
k
1
)
ϕ
(
k
2
)
ϕ
(
k
3
)
ϕ
(
k
4
)
⟩
=
∫
e
−
S
ϕ
(
k
1
)
ϕ
(
k
2
)
ϕ
(
k
3
)
ϕ
(
k
4
)
D
ϕ
Z
{\displaystyle \left\langle \phi (k_{1})\phi (k_{2})\phi (k_{3})\phi (k_{4})\right\rangle ={\frac {\displaystyle \int e^{-S}\phi (k_{1})\phi (k_{2})\phi (k_{3})\phi (k_{4})D\phi }{Z}}}
which in the free field was only nonzero when the momenta k were equal in pairs, is now nonzero for all values of k. The momenta of the insertions φ(ki) can now match up with the momenta of the Xs in the expansion. The insertions should also be thought of as half-lines, four in this case, which carry a momentum k, but one that is not integrated.
The lowest-order contribution comes from the first nontrivial term e−SFX in the Taylor expansion of the action. Wick's theorem requires that the momenta in the X half-lines, the φ(k) factors in X, should match up with the momenta of the external half-lines in pairs. The new contribution is equal to:
λ
1
k
1
2
1
k
2
2
1
k
3
2
1
k
4
2
.
{\displaystyle \lambda {\frac {1}{k_{1}^{2}}}{\frac {1}{k_{2}^{2}}}{\frac {1}{k_{3}^{2}}}{\frac {1}{k_{4}^{2}}}\,.}
The 4! inside X is canceled because there are exactly 4! ways to match the half-lines in X to the external half-lines. Each of these different ways of matching the half-lines together in pairs contributes exactly once, regardless of the values of k1,2,3,4, by Wick's theorem.
==== Feynman diagrams ====
The expansion of the action in powers of X gives a series of terms with progressively higher number of Xs. The contribution from the term with exactly n Xs is called nth order.
The nth order terms has:
4n internal half-lines, which are the factors of φ(k) from the Xs. These all end on a vertex, and are integrated over all possible k.
external half-lines, which are the come from the φ(k) insertions in the integral.
By Wick's theorem, each pair of half-lines must be paired together to make a line, and this line gives a factor of
δ
(
k
1
+
k
2
)
k
1
2
{\displaystyle {\frac {\delta (k_{1}+k_{2})}{k_{1}^{2}}}}
which multiplies the contribution. This means that the two half-lines that make a line are forced to have equal and opposite momentum. The line itself should be labelled by an arrow, drawn parallel to the line, and labeled by the momentum in the line k. The half-line at the tail end of the arrow carries momentum k, while the half-line at the head-end carries momentum −k. If one of the two half-lines is external, this kills the integral over the internal k, since it forces the internal k to be equal to the external k. If both are internal, the integral over k remains.
The diagrams that are formed by linking the half-lines in the Xs with the external half-lines, representing insertions, are the Feynman diagrams of this theory. Each line carries a factor of 1/k2, the propagator, and either goes from vertex to vertex, or ends at an insertion. If it is internal, it is integrated over. At each vertex, the total incoming k is equal to the total outgoing k.
The number of ways of making a diagram by joining half-lines into lines almost completely cancels the factorial factors coming from the Taylor series of the exponential and the 4! at each vertex.
==== Loop order ====
A forest diagram is one where all the internal lines have momentum that is completely determined by the external lines and the condition that the incoming and outgoing momentum are equal at each vertex. The contribution of these diagrams is a product of propagators, without any integration. A tree diagram is a connected forest diagram.
An example of a tree diagram is the one where each of four external lines end on an X. Another is when three external lines end on an X, and the remaining half-line joins up with another X, and the remaining half-lines of this X run off to external lines. These are all also forest diagrams (as every tree is a forest); an example of a forest that is not a tree is when eight external lines end on two Xs.
It is easy to verify that in all these cases, the momenta on all the internal lines is determined by the external momenta and the condition of momentum conservation in each vertex.
A diagram that is not a forest diagram is called a loop diagram, and an example is one where two lines of an X are joined to external lines, while the remaining two lines are joined to each other. The two lines joined to each other can have any momentum at all, since they both enter and leave the same vertex. A more complicated example is one where two Xs are joined to each other by matching the legs one to the other. This diagram has no external lines at all.
The reason loop diagrams are called loop diagrams is because the number of k-integrals that are left undetermined by momentum conservation is equal to the number of independent closed loops in the diagram, where independent loops are counted as in homology theory. The homology is real-valued (actually Rd valued), the value associated with each line is the momentum. The boundary operator takes each line to the sum of the end-vertices with a positive sign at the head and a negative sign at the tail. The condition that the momentum is conserved is exactly the condition that the boundary of the k-valued weighted graph is zero.
A set of valid k-values can be arbitrarily redefined whenever there is a closed loop. A closed loop is a cyclical path of adjacent vertices that never revisits the same vertex. Such a cycle can be thought of as the boundary of a hypothetical 2-cell. The k-labellings of a graph that conserve momentum (i.e. which has zero boundary) up to redefinitions of k (i.e. up to boundaries of 2-cells) define the first homology of a graph. The number of independent momenta that are not determined is then equal to the number of independent homology loops. For many graphs, this is equal to the number of loops as counted in the most intuitive way.
==== Symmetry factors ====
The number of ways to form a given Feynman diagram by joining together half-lines is large, and by Wick's theorem, each way of pairing up the half-lines contributes equally. Often, this completely cancels the factorials in the denominator of each term, but the cancellation is sometimes incomplete.
The uncancelled denominator is called the symmetry factor of the diagram. The contribution of each diagram to the correlation function must be divided by its symmetry factor.
For example, consider the Feynman diagram formed from two external lines joined to one X, and the remaining two half-lines in the X joined to each other. There are 4 × 3 ways to join the external half-lines to the X, and then there is only one way to join the two remaining lines to each other. The X comes divided by 4! = 4 × 3 × 2, but the number of ways to link up the X half lines to make the diagram is only 4 × 3, so the contribution of this diagram is divided by two.
For another example, consider the diagram formed by joining all the half-lines of one X to all the half-lines of another X. This diagram is called a vacuum bubble, because it does not link up to any external lines. There are 4! ways to form this diagram, but the denominator includes a 2! (from the expansion of the exponential, there are two Xs) and two factors of 4!. The contribution is multiplied by 4!/2 × 4! × 4! = 1/48.
Another example is the Feynman diagram formed from two Xs where each X links up to two external lines, and the remaining two half-lines of each X are joined to each other. The number of ways to link an X to two external lines is 4 × 3, and either X could link up to either pair, giving an additional factor of 2. The remaining two half-lines in the two Xs can be linked to each other in two ways, so that the total number of ways to form the diagram is 4 × 3 × 4 × 3 × 2 × 2, while the denominator is 4! × 4! × 2!. The total symmetry factor is 2, and the contribution of this diagram is divided by 2.
The symmetry factor theorem gives the symmetry factor for a general diagram: the contribution of each Feynman diagram must be divided by the order of its group of automorphisms, the number of symmetries that it has.
An automorphism of a Feynman graph is a permutation M of the lines and a permutation N of the vertices with the following properties:
If a line l goes from vertex v to vertex v′, then M(l) goes from N(v) to N(v′). If the line is undirected, as it is for a real scalar field, then M(l) can go from N(v′) to N(v) too.
If a line l ends on an external line, M(l) ends on the same external line.
If there are different types of lines, M(l) should preserve the type.
This theorem has an interpretation in terms of particle-paths: when identical particles are present, the integral over all intermediate particles must not double-count states that differ only by interchanging identical particles.
Proof: To prove this theorem, label all the internal and external lines of a diagram with a unique name. Then form the diagram by linking a half-line to a name and then to the other half line.
Now count the number of ways to form the named diagram. Each permutation of the Xs gives a different pattern of linking names to half-lines, and this is a factor of n!. Each permutation of the half-lines in a single X gives a factor of 4!. So a named diagram can be formed in exactly as many ways as the denominator of the Feynman expansion.
But the number of unnamed diagrams is smaller than the number of named diagram by the order of the automorphism group of the graph.
==== Connected diagrams: linked-cluster theorem ====
Roughly speaking, a Feynman diagram is called connected if all vertices and propagator lines are linked by a sequence of vertices and propagators of the diagram itself. If one views it as an undirected graph it is connected. The remarkable relevance of such diagrams in QFTs is due to the fact that they are sufficient to determine the quantum partition function Z[J]. More precisely, connected Feynman diagrams determine
i
W
[
J
]
≡
ln
Z
[
J
]
.
{\displaystyle iW[J]\equiv \ln Z[J].}
To see this, one should recall that
Z
[
J
]
∝
∑
k
D
k
{\displaystyle Z[J]\propto \sum _{k}{D_{k}}}
with Dk constructed from some (arbitrary) Feynman diagram that can be thought to consist of several connected components Ci. If one encounters ni (identical) copies of a component Ci within the Feynman diagram Dk one has to include a symmetry factor ni!. However, in the end each contribution of a Feynman diagram Dk to the partition function has the generic form
∏
i
C
i
n
i
n
i
!
{\displaystyle \prod _{i}{\frac {C_{i}^{n_{i}}}{n_{i}!}}}
where i labels the (infinitely) many connected Feynman diagrams possible.
A scheme to successively create such contributions from the Dk to Z[J] is obtained by
(
1
0
!
+
C
1
1
!
+
C
1
2
2
!
+
⋯
)
(
1
+
C
2
+
1
2
C
2
2
+
⋯
)
⋯
{\displaystyle \left({\frac {1}{0!}}+{\frac {C_{1}}{1!}}+{\frac {C_{1}^{2}}{2!}}+\cdots \right)\left(1+C_{2}+{\frac {1}{2}}C_{2}^{2}+\cdots \right)\cdots }
and therefore yields
Z
[
J
]
∝
∏
i
∑
n
i
=
0
∞
C
i
n
i
n
i
!
=
exp
∑
i
C
i
∝
exp
W
[
J
]
.
{\displaystyle Z[J]\propto \prod _{i}{\sum _{n_{i}=0}^{\infty }{\frac {C_{i}^{n_{i}}}{n_{i}!}}}=\exp {\sum _{i}{C_{i}}}\propto \exp {W[J]}\,.}
To establish the normalization Z0 = exp W[0] = 1 one simply calculates all connected vacuum diagrams, i.e., the diagrams without any sources J (sometimes referred to as external legs of a Feynman diagram).
The linked-cluster theorem was first proved to order four by Keith Brueckner in 1955, and for infinite orders by Jeffrey Goldstone in 1957.
==== Vacuum bubbles ====
An immediate consequence of the linked-cluster theorem is that all vacuum bubbles, diagrams without external lines, cancel when calculating correlation functions. A correlation function is given by a ratio of path-integrals:
⟨
ϕ
1
(
x
1
)
⋯
ϕ
n
(
x
n
)
⟩
=
∫
e
−
S
ϕ
1
(
x
1
)
⋯
ϕ
n
(
x
n
)
D
ϕ
∫
e
−
S
D
ϕ
.
{\displaystyle \left\langle \phi _{1}(x_{1})\cdots \phi _{n}(x_{n})\right\rangle ={\frac {\displaystyle \int e^{-S}\phi _{1}(x_{1})\cdots \phi _{n}(x_{n})\,D\phi }{\displaystyle \int e^{-S}\,D\phi }}\,.}
The top is the sum over all Feynman diagrams, including disconnected diagrams that do not link up to external lines at all. In terms of the connected diagrams, the numerator includes the same contributions of vacuum bubbles as the denominator:
∫
e
−
S
ϕ
1
(
x
1
)
⋯
ϕ
n
(
x
n
)
D
ϕ
=
(
∑
E
i
)
(
exp
(
∑
i
C
i
)
)
.
{\displaystyle \int e^{-S}\phi _{1}(x_{1})\cdots \phi _{n}(x_{n})\,D\phi =\left(\sum E_{i}\right)\left(\exp \left(\sum _{i}C_{i}\right)\right)\,.}
Where the sum over E diagrams includes only those diagrams each of whose connected components end on at least one external line. The vacuum bubbles are the same whatever the external lines, and give an overall multiplicative factor. The denominator is the sum over all vacuum bubbles, and dividing gets rid of the second factor.
The vacuum bubbles then are only useful for determining Z itself, which from the definition of the path integral is equal to:
Z
=
∫
e
−
S
D
ϕ
=
e
−
H
T
=
e
−
ρ
V
{\displaystyle Z=\int e^{-S}D\phi =e^{-HT}=e^{-\rho V}}
where ρ is the energy density in the vacuum. Each vacuum bubble contains a factor of δ(k) zeroing the total k at each vertex, and when there are no external lines, this contains a factor of δ(0), because the momentum conservation is over-enforced. In finite volume, this factor can be identified as the total volume of space time. Dividing by the volume, the remaining integral for the vacuum bubble has an interpretation: it is a contribution to the energy density of the vacuum.
==== Sources ====
Correlation functions are the sum of the connected Feynman diagrams, but the formalism treats the connected and disconnected diagrams differently. Internal lines end on vertices, while external lines go off to insertions. Introducing sources unifies the formalism, by making new vertices where one line can end.
Sources are external fields, fields that contribute to the action, but are not dynamical variables. A scalar field source is another scalar field h that contributes a term to the (Lorentz) Lagrangian:
∫
h
(
x
)
ϕ
(
x
)
d
d
x
=
∫
h
(
k
)
ϕ
(
k
)
d
d
k
{\displaystyle \int h(x)\phi (x)\,d^{d}x=\int h(k)\phi (k)\,d^{d}k\,}
In the Feynman expansion, this contributes H terms with one half-line ending on a vertex. Lines in a Feynman diagram can now end either on an X vertex, or on an H vertex, and only one line enters an H vertex. The Feynman rule for an H vertex is that a line from an H with momentum k gets a factor of h(k).
The sum of the connected diagrams in the presence of sources includes a term for each connected diagram in the absence of sources, except now the diagrams can end on the source. Traditionally, a source is represented by a little "×" with one line extending out, exactly as an insertion.
log
(
Z
[
h
]
)
=
∑
n
,
C
h
(
k
1
)
h
(
k
2
)
⋯
h
(
k
n
)
C
(
k
1
,
⋯
,
k
n
)
{\displaystyle \log {\big (}Z[h]{\big )}=\sum _{n,C}h(k_{1})h(k_{2})\cdots h(k_{n})C(k_{1},\cdots ,k_{n})\,}
where C(k1,...,kn) is the connected diagram with n external lines carrying momentum as indicated. The sum is over all connected diagrams, as before.
The field h is not dynamical, which means that there is no path integral over h: h is just a parameter in the Lagrangian, which varies from point to point. The path integral for the field is:
Z
[
h
]
=
∫
e
i
S
+
i
∫
h
ϕ
D
ϕ
{\displaystyle Z[h]=\int e^{iS+i\int h\phi }\,D\phi \,}
and it is a function of the values of h at every point. One way to interpret this expression is that it is taking the Fourier transform in field space. If there is a probability density on Rn, the Fourier transform of the probability density is:
∫
ρ
(
y
)
e
i
k
y
d
n
y
=
⟨
e
i
k
y
⟩
=
⟨
∏
i
=
1
n
e
i
h
i
y
i
⟩
{\displaystyle \int \rho (y)e^{iky}\,d^{n}y=\left\langle e^{iky}\right\rangle =\left\langle \prod _{i=1}^{n}e^{ih_{i}y_{i}}\right\rangle \,}
The Fourier transform is the expectation of an oscillatory exponential. The path integral in the presence of a source h(x) is:
Z
[
h
]
=
∫
e
i
S
e
i
∫
x
h
(
x
)
ϕ
(
x
)
D
ϕ
=
⟨
e
i
h
ϕ
⟩
{\displaystyle Z[h]=\int e^{iS}e^{i\int _{x}h(x)\phi (x)}\,D\phi =\left\langle e^{ih\phi }\right\rangle }
which, on a lattice, is the product of an oscillatory exponential for each field value:
⟨
∏
x
e
i
h
x
ϕ
x
⟩
{\displaystyle \left\langle \prod _{x}e^{ih_{x}\phi _{x}}\right\rangle }
The Fourier transform of a delta-function is a constant, which gives a formal expression for a delta function:
δ
(
x
−
y
)
=
∫
e
i
k
(
x
−
y
)
d
k
{\displaystyle \delta (x-y)=\int e^{ik(x-y)}\,dk}
This tells you what a field delta function looks like in a path-integral. For two scalar fields φ and η,
δ
(
ϕ
−
η
)
=
∫
e
i
h
(
x
)
(
ϕ
(
x
)
−
η
(
x
)
)
d
d
x
D
h
,
{\displaystyle \delta (\phi -\eta )=\int e^{ih(x){\big (}\phi (x)-\eta (x){\big )}\,d^{d}x}\,Dh\,,}
which integrates over the Fourier transform coordinate, over h. This expression is useful for formally changing field coordinates in the path integral, much as a delta function is used to change coordinates in an ordinary multi-dimensional integral.
The partition function is now a function of the field h, and the physical partition function is the value when h is the zero function:
The correlation functions are derivatives of the path integral with respect to the source:
⟨
ϕ
(
x
)
⟩
=
1
Z
∂
∂
h
(
x
)
Z
[
h
]
=
∂
∂
h
(
x
)
log
(
Z
[
h
]
)
.
{\displaystyle \left\langle \phi (x)\right\rangle ={\frac {1}{Z}}{\frac {\partial }{\partial h(x)}}Z[h]={\frac {\partial }{\partial h(x)}}\log {\big (}Z[h]{\big )}\,.}
In Euclidean space, source contributions to the action can still appear with a factor of i, so that they still do a Fourier transform.
=== Spin 1/2; "photons" and "ghosts" ===
==== Spin 1/2: Grassmann integrals ====
The field path integral can be extended to the Fermi case, but only if the notion of integration is expanded. A Grassmann integral of a free Fermi field is a high-dimensional determinant or Pfaffian, which defines the new type of Gaussian integration appropriate for Fermi fields.
The two fundamental formulas of Grassmann integration are:
∫
e
M
i
j
ψ
¯
i
ψ
j
D
ψ
¯
D
ψ
=
D
e
t
(
M
)
,
{\displaystyle \int e^{M_{ij}{\bar {\psi }}^{i}\psi ^{j}}\,D{\bar {\psi }}\,D\psi =\mathrm {Det} (M)\,,}
where M is an arbitrary matrix and ψ, ψ are independent Grassmann variables for each index i, and
∫
e
1
2
A
i
j
ψ
i
ψ
j
D
ψ
=
P
f
a
f
f
(
A
)
,
{\displaystyle \int e^{{\frac {1}{2}}A_{ij}\psi ^{i}\psi ^{j}}\,D\psi =\mathrm {Pfaff} (A)\,,}
where A is an antisymmetric matrix, ψ is a collection of Grassmann variables, and the 1/2 is to prevent double-counting (since ψiψj = −ψjψi).
In matrix notation, where ψ and η are Grassmann-valued row vectors, η and ψ are Grassmann-valued column vectors, and M is a real-valued matrix:
Z
=
∫
e
ψ
¯
M
ψ
+
η
¯
ψ
+
ψ
¯
η
D
ψ
¯
D
ψ
=
∫
e
(
ψ
¯
+
η
¯
M
−
1
)
M
(
ψ
+
M
−
1
η
)
−
η
¯
M
−
1
η
D
ψ
¯
D
ψ
=
D
e
t
(
M
)
e
−
η
¯
M
−
1
η
,
{\displaystyle Z=\int e^{{\bar {\psi }}M\psi +{\bar {\eta }}\psi +{\bar {\psi }}\eta }\,D{\bar {\psi }}\,D\psi =\int e^{\left({\bar {\psi }}+{\bar {\eta }}M^{-1}\right)M\left(\psi +M^{-1}\eta \right)-{\bar {\eta }}M^{-1}\eta }\,D{\bar {\psi }}\,D\psi =\mathrm {Det} (M)e^{-{\bar {\eta }}M^{-1}\eta }\,,}
where the last equality is a consequence of the translation invariance of the Grassmann integral. The Grassmann variables η are external sources for ψ, and differentiating with respect to η pulls down factors of ψ.
⟨
ψ
¯
ψ
⟩
=
1
Z
∂
∂
η
∂
∂
η
¯
Z
|
η
=
η
¯
=
0
=
M
−
1
{\displaystyle \left\langle {\bar {\psi }}\psi \right\rangle ={\frac {1}{Z}}{\frac {\partial }{\partial \eta }}{\frac {\partial }{\partial {\bar {\eta }}}}Z|_{\eta ={\bar {\eta }}=0}=M^{-1}}
again, in a schematic matrix notation. The meaning of the formula above is that the derivative with respect to the appropriate component of η and η gives the matrix element of M−1. This is exactly analogous to the bosonic path integration formula for a Gaussian integral of a complex bosonic field:
∫
e
ϕ
∗
M
ϕ
+
h
∗
ϕ
+
ϕ
∗
h
D
ϕ
∗
D
ϕ
=
e
h
∗
M
−
1
h
D
e
t
(
M
)
{\displaystyle \int e^{\phi ^{*}M\phi +h^{*}\phi +\phi ^{*}h}\,D\phi ^{*}\,D\phi ={\frac {e^{h^{*}M^{-1}h}}{\mathrm {Det} (M)}}}
⟨
ϕ
∗
ϕ
⟩
=
1
Z
∂
∂
h
∂
∂
h
∗
Z
|
h
=
h
∗
=
0
=
M
−
1
.
{\displaystyle \left\langle \phi ^{*}\phi \right\rangle ={\frac {1}{Z}}{\frac {\partial }{\partial h}}{\frac {\partial }{\partial h^{*}}}Z|_{h=h^{*}=0}=M^{-1}\,.}
So that the propagator is the inverse of the matrix in the quadratic part of the action in both the Bose and Fermi case.
For real Grassmann fields, for Majorana fermions, the path integral is a Pfaffian times a source quadratic form, and the formulas give the square root of the determinant, just as they do for real Bosonic fields. The propagator is still the inverse of the quadratic part.
The free Dirac Lagrangian:
∫
ψ
¯
(
γ
μ
∂
μ
−
m
)
ψ
{\displaystyle \int {\bar {\psi }}\left(\gamma ^{\mu }\partial _{\mu }-m\right)\psi }
formally gives the equations of motion and the anticommutation relations of the Dirac field, just as the Klein Gordon Lagrangian in an ordinary path integral gives the equations of motion and commutation relations of the scalar field. By using the spatial Fourier transform of the Dirac field as a new basis for the Grassmann algebra, the quadratic part of the Dirac action becomes simple to invert:
S
=
∫
k
ψ
¯
(
i
γ
μ
k
μ
−
m
)
ψ
.
{\displaystyle S=\int _{k}{\bar {\psi }}\left(i\gamma ^{\mu }k_{\mu }-m\right)\psi \,.}
The propagator is the inverse of the matrix M linking ψ(k) and ψ(k), since different values of k do not mix together.
⟨
ψ
¯
(
k
′
)
ψ
(
k
)
⟩
=
δ
(
k
+
k
′
)
1
γ
⋅
k
−
m
=
δ
(
k
+
k
′
)
γ
⋅
k
+
m
k
2
−
m
2
{\displaystyle \left\langle {\bar {\psi }}(k')\psi (k)\right\rangle =\delta (k+k'){\frac {1}{\gamma \cdot k-m}}=\delta (k+k'){\frac {\gamma \cdot k+m}{k^{2}-m^{2}}}}
The analog of Wick's theorem matches ψ and ψ in pairs:
⟨
ψ
¯
(
k
1
)
ψ
¯
(
k
2
)
⋯
ψ
¯
(
k
n
)
ψ
(
k
1
′
)
⋯
ψ
(
k
n
)
⟩
=
∑
p
a
i
r
i
n
g
s
(
−
1
)
S
∏
p
a
i
r
s
i
,
j
δ
(
k
i
−
k
j
)
1
γ
⋅
k
i
−
m
{\displaystyle \left\langle {\bar {\psi }}(k_{1}){\bar {\psi }}(k_{2})\cdots {\bar {\psi }}(k_{n})\psi (k'_{1})\cdots \psi (k_{n})\right\rangle =\sum _{\mathrm {pairings} }(-1)^{S}\prod _{\mathrm {pairs} \;i,j}\delta \left(k_{i}-k_{j}\right){\frac {1}{\gamma \cdot k_{i}-m}}}
where S is the sign of the permutation that reorders the sequence of ψ and ψ to put the ones that are paired up to make the delta-functions next to each other, with the ψ coming right before the ψ. Since a ψ, ψ pair is a commuting element of the Grassmann algebra, it does not matter what order the pairs are in. If more than one ψ, ψ pair have the same k, the integral is zero, and it is easy to check that the sum over pairings gives zero in this case (there are always an even number of them). This is the Grassmann analog of the higher Gaussian moments that completed the Bosonic Wick's theorem earlier.
The rules for spin-1/2 Dirac particles are as follows: The propagator is the inverse of the Dirac operator, the lines have arrows just as for a complex scalar field, and the diagram acquires an overall factor of −1 for each closed Fermi loop. If there are an odd number of Fermi loops, the diagram changes sign. Historically, the −1 rule was very difficult for Feynman to discover. He discovered it after a long process of trial and error, since he lacked a proper theory of Grassmann integration.
The rule follows from the observation that the number of Fermi lines at a vertex is always even. Each term in the Lagrangian must always be Bosonic. A Fermi loop is counted by following Fermionic lines until one comes back to the starting point, then removing those lines from the diagram. Repeating this process eventually erases all the Fermionic lines: this is the Euler algorithm to 2-color a graph, which works whenever each vertex has even degree. The number of steps in the Euler algorithm is only equal to the number of independent Fermionic homology cycles in the common special case that all terms in the Lagrangian are exactly quadratic in the Fermi fields, so that each vertex has exactly two Fermionic lines. When there are four-Fermi interactions (like in the Fermi effective theory of the weak nuclear interactions) there are more k-integrals than Fermi loops. In this case, the counting rule should apply the Euler algorithm by pairing up the Fermi lines at each vertex into pairs that together form a bosonic factor of the term in the Lagrangian, and when entering a vertex by one line, the algorithm should always leave with the partner line.
To clarify and prove the rule, consider a Feynman diagram formed from vertices, terms in the Lagrangian, with Fermion fields. The full term is Bosonic, it is a commuting element of the Grassmann algebra, so the order in which the vertices appear is not important. The Fermi lines are linked into loops, and when traversing the loop, one can reorder the vertex terms one after the other as one goes around without any sign cost. The exception is when you return to the starting point, and the final half-line must be joined with the unlinked first half-line. This requires one permutation to move the last ψ to go in front of the first ψ, and this gives the sign.
This rule is the only visible effect of the exclusion principle in internal lines. When there are external lines, the amplitudes are antisymmetric when two Fermi insertions for identical particles are interchanged. This is automatic in the source formalism, because the sources for Fermi fields are themselves Grassmann valued.
==== Spin 1: photons ====
The naive propagator for photons is infinite, since the Lagrangian for the A-field is:
S
=
∫
1
4
F
μ
ν
F
μ
ν
=
∫
−
1
2
(
∂
μ
A
ν
∂
μ
A
ν
−
∂
μ
A
μ
∂
ν
A
ν
)
.
{\displaystyle S=\int {\tfrac {1}{4}}F^{\mu \nu }F_{\mu \nu }=\int -{\tfrac {1}{2}}\left(\partial ^{\mu }A_{\nu }\partial _{\mu }A^{\nu }-\partial ^{\mu }A_{\mu }\partial _{\nu }A^{\nu }\right)\,.}
The quadratic form defining the propagator is non-invertible. The reason is the gauge invariance of the field; adding a gradient to A does not change the physics.
To fix this problem, one needs to fix a gauge. The most convenient way is to demand that the divergence of A is some function f, whose value is random from point to point. It does no harm to integrate over the values of f, since it only determines the choice of gauge. This procedure inserts the following factor into the path integral for A:
∫
δ
(
∂
μ
A
μ
−
f
)
e
−
f
2
2
D
f
.
{\displaystyle \int \delta \left(\partial _{\mu }A^{\mu }-f\right)e^{-{\frac {f^{2}}{2}}}\,Df\,.}
The first factor, the delta function, fixes the gauge. The second factor sums over different values of f that are inequivalent gauge fixings. This is simply
e
−
(
∂
μ
A
μ
)
2
2
.
{\displaystyle e^{-{\frac {\left(\partial _{\mu }A_{\mu }\right)^{2}}{2}}}\,.}
The additional contribution from gauge-fixing cancels the second half of the free Lagrangian, giving the Feynman Lagrangian:
S
=
∫
∂
μ
A
ν
∂
μ
A
ν
{\displaystyle S=\int \partial ^{\mu }A^{\nu }\partial _{\mu }A_{\nu }}
which is just like four independent free scalar fields, one for each component of A. The Feynman propagator is:
⟨
A
μ
(
k
)
A
ν
(
k
′
)
⟩
=
δ
(
k
+
k
′
)
g
μ
ν
k
2
.
{\displaystyle \left\langle A_{\mu }(k)A_{\nu }(k')\right\rangle =\delta \left(k+k'\right){\frac {g_{\mu \nu }}{k^{2}}}.}
The one difference is that the sign of one propagator is wrong in the Lorentz case: the timelike component has an opposite sign propagator. This means that these particle states have negative norm—they are not physical states. In the case of photons, it is easy to show by diagram methods that these states are not physical—their contribution cancels with longitudinal photons to only leave two physical photon polarization contributions for any value of k.
If the averaging over f is done with a coefficient different from 1/2, the two terms do not cancel completely. This gives a covariant Lagrangian with a coefficient
λ
{\displaystyle \lambda }
, which does not affect anything:
S
=
∫
1
2
(
∂
μ
A
ν
∂
μ
A
ν
−
λ
(
∂
μ
A
μ
)
2
)
{\displaystyle S=\int {\tfrac {1}{2}}\left(\partial ^{\mu }A^{\nu }\partial _{\mu }A_{\nu }-\lambda \left(\partial _{\mu }A^{\mu }\right)^{2}\right)}
and the covariant propagator for QED is:
⟨
A
μ
(
k
)
A
ν
(
k
′
)
⟩
=
δ
(
k
+
k
′
)
g
μ
ν
−
λ
k
μ
k
ν
k
2
k
2
.
{\displaystyle \left\langle A_{\mu }(k)A_{\nu }(k')\right\rangle =\delta \left(k+k'\right){\frac {g_{\mu \nu }-\lambda {\frac {k_{\mu }k_{\nu }}{k^{2}}}}{k^{2}}}.}
==== Spin 1: non-Abelian ghosts ====
To find the Feynman rules for non-Abelian gauge fields, the procedure that performs the gauge fixing must be carefully corrected to account for a change of variables in the path-integral.
The gauge fixing factor has an extra determinant from popping the delta function:
δ
(
∂
μ
A
μ
−
f
)
e
−
f
2
2
det
M
{\displaystyle \delta \left(\partial _{\mu }A_{\mu }-f\right)e^{-{\frac {f^{2}}{2}}}\det M}
To find the form of the determinant, consider first a simple two-dimensional integral of a function f that depends only on r, not on the angle θ. Inserting an integral over θ:
∫
f
(
r
)
d
x
d
y
=
∫
f
(
r
)
∫
d
θ
δ
(
y
)
|
d
y
d
θ
|
d
x
d
y
{\displaystyle \int f(r)\,dx\,dy=\int f(r)\int d\theta \,\delta (y)\left|{\frac {dy}{d\theta }}\right|\,dx\,dy}
The derivative-factor ensures that popping the delta function in θ removes the integral. Exchanging the order of integration,
∫
f
(
r
)
d
x
d
y
=
∫
d
θ
∫
f
(
r
)
δ
(
y
)
|
d
y
d
θ
|
d
x
d
y
{\displaystyle \int f(r)\,dx\,dy=\int d\theta \,\int f(r)\delta (y)\left|{\frac {dy}{d\theta }}\right|\,dx\,dy}
but now the delta-function can be popped in y,
∫
f
(
r
)
d
x
d
y
=
∫
d
θ
0
∫
f
(
x
)
|
d
y
d
θ
|
d
x
.
{\displaystyle \int f(r)\,dx\,dy=\int d\theta _{0}\,\int f(x)\left|{\frac {dy}{d\theta }}\right|\,dx\,.}
The integral over θ just gives an overall factor of 2π, while the rate of change of y with a change in θ is just x, so this exercise reproduces the standard formula for polar integration of a radial function:
∫
f
(
r
)
d
x
d
y
=
2
π
∫
f
(
x
)
x
d
x
{\displaystyle \int f(r)\,dx\,dy=2\pi \int f(x)x\,dx}
In the path-integral for a nonabelian gauge field, the analogous manipulation is:
∫
D
A
∫
δ
(
F
(
A
)
)
det
(
∂
F
∂
G
)
D
G
e
i
S
=
∫
D
G
∫
δ
(
F
(
A
)
)
det
(
∂
F
∂
G
)
e
i
S
{\displaystyle \int DA\int \delta {\big (}F(A){\big )}\det \left({\frac {\partial F}{\partial G}}\right)\,DGe^{iS}=\int DG\int \delta {\big (}F(A){\big )}\det \left({\frac {\partial F}{\partial G}}\right)e^{iS}\,}
The factor in front is the volume of the gauge group, and it contributes a constant, which can be discarded. The remaining integral is over the gauge fixed action.
∫
det
(
∂
F
∂
G
)
e
i
S
G
F
D
A
{\displaystyle \int \det \left({\frac {\partial F}{\partial G}}\right)e^{iS_{GF}}\,DA\,}
To get a covariant gauge, the gauge fixing condition is the same as in the Abelian case:
∂
μ
A
μ
=
f
,
{\displaystyle \partial _{\mu }A^{\mu }=f\,,}
Whose variation under an infinitesimal gauge transformation is given by:
∂
μ
D
μ
α
,
{\displaystyle \partial _{\mu }\,D_{\mu }\alpha \,,}
where α is the adjoint valued element of the Lie algebra at every point that performs the infinitesimal gauge transformation. This adds the Faddeev Popov determinant to the action:
det
(
∂
μ
D
μ
)
{\displaystyle \det \left(\partial _{\mu }\,D_{\mu }\right)\,}
which can be rewritten as a Grassmann integral by introducing ghost fields:
∫
e
η
¯
∂
μ
D
μ
η
D
η
¯
D
η
{\displaystyle \int e^{{\bar {\eta }}\partial _{\mu }\,D^{\mu }\eta }\,D{\bar {\eta }}\,D\eta \,}
The determinant is independent of f, so the path-integral over f can give the Feynman propagator (or a covariant propagator) by choosing the measure for f as in the abelian case. The full gauge fixed action is then the Yang Mills action in Feynman gauge with an additional ghost action:
S
=
∫
Tr
∂
μ
A
ν
∂
μ
A
ν
+
f
j
k
i
∂
ν
A
i
μ
A
μ
j
A
ν
k
+
f
j
r
i
f
k
l
r
A
i
A
j
A
k
A
l
+
Tr
∂
μ
η
¯
∂
μ
η
+
η
¯
A
j
η
{\displaystyle S=\int \operatorname {Tr} \partial _{\mu }A_{\nu }\partial ^{\mu }A^{\nu }+f_{jk}^{i}\partial ^{\nu }A_{i}^{\mu }A_{\mu }^{j}A_{\nu }^{k}+f_{jr}^{i}f_{kl}^{r}A_{i}A_{j}A^{k}A^{l}+\operatorname {Tr} \partial _{\mu }{\bar {\eta }}\partial ^{\mu }\eta +{\bar {\eta }}A_{j}\eta \,}
The diagrams are derived from this action. The propagator for the spin-1 fields has the usual Feynman form. There are vertices of degree 3 with momentum factors whose couplings are the structure constants, and vertices of degree 4 whose couplings are products of structure constants. There are additional ghost loops, which cancel out timelike and longitudinal states in A loops.
In the Abelian case, the determinant for covariant gauges does not depend on A, so the ghosts do not contribute to the connected diagrams.
== Particle-path representation ==
Feynman diagrams were originally discovered by Feynman, by trial and error, as a way to represent the contribution to the S-matrix from different classes of particle trajectories.
=== Schwinger representation ===
The Euclidean scalar propagator has a suggestive representation:
1
p
2
+
m
2
=
∫
0
∞
e
−
τ
(
p
2
+
m
2
)
d
τ
{\displaystyle {\frac {1}{p^{2}+m^{2}}}=\int _{0}^{\infty }e^{-\tau \left(p^{2}+m^{2}\right)}\,d\tau }
The meaning of this identity (which is an elementary integration) is made clearer by Fourier transforming to real space.
Δ
(
x
)
=
∫
0
∞
d
τ
e
−
m
2
τ
1
(
4
π
τ
)
d
/
2
e
−
x
2
4
τ
{\displaystyle \Delta (x)=\int _{0}^{\infty }d\tau e^{-m^{2}\tau }{\frac {1}{({4\pi \tau })^{d/2}}}e^{\frac {-x^{2}}{4\tau }}}
The contribution at any one value of τ to the propagator is a Gaussian of width √τ. The total propagation function from 0 to x is a weighted sum over all proper times τ of a normalized Gaussian, the probability of ending up at x after a random walk of time τ.
The path-integral representation for the propagator is then:
Δ
(
x
)
=
∫
0
∞
d
τ
∫
D
X
e
−
∫
0
τ
(
x
˙
2
2
+
m
2
)
d
τ
′
{\displaystyle \Delta (x)=\int _{0}^{\infty }d\tau \int DX\,e^{-\int \limits _{0}^{\tau }\left({\frac {{\dot {x}}^{2}}{2}}+m^{2}\right)d\tau '}}
which is a path-integral rewrite of the Schwinger representation.
The Schwinger representation is both useful for making manifest the particle aspect of the propagator, and for symmetrizing denominators of loop diagrams.
=== Combining denominators ===
The Schwinger representation has an immediate practical application to loop diagrams. For example, for the diagram in the φ4 theory formed by joining two xs together in two half-lines, and making the remaining lines external, the integral over the internal propagators in the loop is:
∫
k
1
k
2
+
m
2
1
(
k
+
p
)
2
+
m
2
.
{\displaystyle \int _{k}{\frac {1}{k^{2}+m^{2}}}{\frac {1}{(k+p)^{2}+m^{2}}}\,.}
Here one line carries momentum k and the other k + p. The asymmetry can be fixed by putting everything in the Schwinger representation.
∫
t
,
t
′
e
−
t
(
k
2
+
m
2
)
−
t
′
(
(
k
+
p
)
2
+
m
2
)
d
t
d
t
′
.
{\displaystyle \int _{t,t'}e^{-t(k^{2}+m^{2})-t'\left((k+p)^{2}+m^{2}\right)}\,dt\,dt'\,.}
Now the exponent mostly depends on t + t′,
∫
t
,
t
′
e
−
(
t
+
t
′
)
(
k
2
+
m
2
)
−
t
′
2
p
⋅
k
−
t
′
p
2
,
{\displaystyle \int _{t,t'}e^{-(t+t')(k^{2}+m^{2})-t'2p\cdot k-t'p^{2}}\,,}
except for the asymmetrical little bit. Defining the variable u = t + t′ and v = t′/u, the variable u goes from 0 to ∞, while v goes from 0 to 1. The variable u is the total proper time for the loop, while v parametrizes the fraction of the proper time on the top of the loop versus the bottom.
The Jacobian for this transformation of variables is easy to work out from the identities:
d
(
u
v
)
=
d
t
′
d
u
=
d
t
+
d
t
′
,
{\displaystyle d(uv)=dt'\quad du=dt+dt'\,,}
and "wedging" gives
u
d
u
∧
d
v
=
d
t
∧
d
t
′
{\displaystyle u\,du\wedge dv=dt\wedge dt'\,}
.
This allows the u integral to be evaluated explicitly:
∫
u
,
v
u
e
−
u
(
k
2
+
m
2
+
v
2
p
⋅
k
+
v
p
2
)
=
∫
1
(
k
2
+
m
2
+
v
2
p
⋅
k
−
v
p
2
)
2
d
v
{\displaystyle \int _{u,v}ue^{-u\left(k^{2}+m^{2}+v2p\cdot k+vp^{2}\right)}=\int {\frac {1}{\left(k^{2}+m^{2}+v2p\cdot k-vp^{2}\right)^{2}}}\,dv}
leaving only the v-integral. This method, invented by Schwinger but usually attributed to Feynman, is called combining denominator. Abstractly, it is the elementary identity:
1
A
B
=
∫
0
1
1
(
v
A
+
(
1
−
v
)
B
)
2
d
v
{\displaystyle {\frac {1}{AB}}=\int _{0}^{1}{\frac {1}{{\big (}vA+(1-v)B{\big )}^{2}}}\,dv}
But this form does not provide the physical motivation for introducing v; v is the proportion of proper time on one of the legs of the loop.
Once the denominators are combined, a shift in k to k′ = k + vp symmetrizes everything:
∫
0
1
∫
1
(
k
2
+
m
2
+
2
v
p
⋅
k
+
v
p
2
)
2
d
k
d
v
=
∫
0
1
∫
1
(
k
′
2
+
m
2
+
v
(
1
−
v
)
p
2
)
2
d
k
′
d
v
{\displaystyle \int _{0}^{1}\int {\frac {1}{\left(k^{2}+m^{2}+2vp\cdot k+vp^{2}\right)^{2}}}\,dk\,dv=\int _{0}^{1}\int {\frac {1}{\left(k'^{2}+m^{2}+v(1-v)p^{2}\right)^{2}}}\,dk'\,dv}
This form shows that the moment that p2 is more negative than four times the mass of the particle in the loop, which happens in a physical region of Lorentz space, the integral has a cut. This is exactly when the external momentum can create physical particles.
When the loop has more vertices, there are more denominators to combine:
∫
d
k
1
k
2
+
m
2
1
(
k
+
p
1
)
2
+
m
2
⋯
1
(
k
+
p
n
)
2
+
m
2
{\displaystyle \int dk\,{\frac {1}{k^{2}+m^{2}}}{\frac {1}{(k+p_{1})^{2}+m^{2}}}\cdots {\frac {1}{(k+p_{n})^{2}+m^{2}}}}
The general rule follows from the Schwinger prescription for n + 1 denominators:
1
D
0
D
1
⋯
D
n
=
∫
0
∞
⋯
∫
0
∞
e
−
u
0
D
0
⋯
−
u
n
D
n
d
u
0
⋯
d
u
n
.
{\displaystyle {\frac {1}{D_{0}D_{1}\cdots D_{n}}}=\int _{0}^{\infty }\cdots \int _{0}^{\infty }e^{-u_{0}D_{0}\cdots -u_{n}D_{n}}\,du_{0}\cdots du_{n}\,.}
The integral over the Schwinger parameters ui can be split up as before into an integral over the total proper time u = u0 + u1 ... + un and an integral over the fraction of the proper time in all but the first segment of the loop vi = ui/u for i ∈ {1,2,...,n}. The vi are positive and add up to less than 1, so that the v integral is over an n-dimensional simplex.
The Jacobian for the coordinate transformation can be worked out as before:
d
u
=
d
u
0
+
d
u
1
⋯
+
d
u
n
{\displaystyle du=du_{0}+du_{1}\cdots +du_{n}\,}
d
(
u
v
i
)
=
d
u
i
.
{\displaystyle d(uv_{i})=du_{i}\,.}
Wedging all these equations together, one obtains
u
n
d
u
∧
d
v
1
∧
d
v
2
⋯
∧
d
v
n
=
d
u
0
∧
d
u
1
⋯
∧
d
u
n
.
{\displaystyle u^{n}\,du\wedge dv_{1}\wedge dv_{2}\cdots \wedge dv_{n}=du_{0}\wedge du_{1}\cdots \wedge du_{n}\,.}
This gives the integral:
∫
0
∞
∫
s
i
m
p
l
e
x
u
n
e
−
u
(
v
0
D
0
+
v
1
D
1
+
v
2
D
2
⋯
+
v
n
D
n
)
d
v
1
⋯
d
v
n
d
u
,
{\displaystyle \int _{0}^{\infty }\int _{\mathrm {simplex} }u^{n}e^{-u\left(v_{0}D_{0}+v_{1}D_{1}+v_{2}D_{2}\cdots +v_{n}D_{n}\right)}\,dv_{1}\cdots dv_{n}\,du\,,}
where the simplex is the region defined by the conditions
v
i
>
0
and
∑
i
=
1
n
v
i
<
1
{\displaystyle v_{i}>0\quad {\mbox{and}}\quad \sum _{i=1}^{n}v_{i}<1}
as well as
v
0
=
1
−
∑
i
=
1
n
v
i
.
{\displaystyle v_{0}=1-\sum _{i=1}^{n}v_{i}\,.}
Performing the u integral gives the general prescription for combining denominators:
1
D
0
⋯
D
n
=
n
!
∫
s
i
m
p
l
e
x
1
(
v
0
D
0
+
v
1
D
1
⋯
+
v
n
D
n
)
n
+
1
d
v
1
d
v
2
⋯
d
v
n
{\displaystyle {\frac {1}{D_{0}\cdots D_{n}}}=n!\int _{\mathrm {simplex} }{\frac {1}{\left(v_{0}D_{0}+v_{1}D_{1}\cdots +v_{n}D_{n}\right)^{n+1}}}\,dv_{1}\,dv_{2}\cdots dv_{n}}
Since the numerator of the integrand is not involved, the same prescription works for any loop, no matter what the spins are carried by the legs. The interpretation of the parameters vi is that they are the fraction of the total proper time spent on each leg.
=== Scattering ===
The correlation functions of a quantum field theory describe the scattering of particles. The definition of "particle" in relativistic field theory is not self-evident, because if you try to determine the position so that the uncertainty is less than the compton wavelength, the uncertainty in energy is large enough to produce more particles and antiparticles of the same type from the vacuum. This means that the notion of a single-particle state is to some extent incompatible with the notion of an object localized in space.
In the 1930s, Wigner gave a mathematical definition for single-particle states: they are a collection of states that form an irreducible representation of the Poincaré group. Single particle states describe an object with a finite mass, a well defined momentum, and a spin. This definition is fine for protons and neutrons, electrons and photons, but it excludes quarks, which are permanently confined, so the modern point of view is more accommodating: a particle is anything whose interaction can be described in terms of Feynman diagrams, which have an interpretation as a sum over particle trajectories.
A field operator can act to produce a one-particle state from the vacuum, which means that the field operator φ(x) produces a superposition of Wigner particle states. In the free field theory, the field produces one particle states only. But when there are interactions, the field operator can also produce 3-particle, 5-particle (if there is no +/− symmetry also 2, 4, 6 particle) states too. To compute the scattering amplitude for single particle states only requires a careful limit, sending the fields to infinity and integrating over space to get rid of the higher-order corrections.
The relation between scattering and correlation functions is the LSZ-theorem: The scattering amplitude for n particles to go to m particles in a scattering event is the given by the sum of the Feynman diagrams that go into the correlation function for n + m field insertions, leaving out the propagators for the external legs.
For example, for the λφ4 interaction of the previous section, the order λ contribution to the (Lorentz) correlation function is:
⟨
ϕ
(
k
1
)
ϕ
(
k
2
)
ϕ
(
k
3
)
ϕ
(
k
4
)
⟩
=
i
k
1
2
i
k
2
2
i
k
3
2
i
k
4
2
i
λ
{\displaystyle \left\langle \phi (k_{1})\phi (k_{2})\phi (k_{3})\phi (k_{4})\right\rangle ={\frac {i}{k_{1}^{2}}}{\frac {i}{k_{2}^{2}}}{\frac {i}{k_{3}^{2}}}{\frac {i}{k_{4}^{2}}}i\lambda \,}
Stripping off the external propagators, that is, removing the factors of i/k2, gives the invariant scattering amplitude M:
M
=
i
λ
{\displaystyle M=i\lambda \,}
which is a constant, independent of the incoming and outgoing momentum. The interpretation of the scattering amplitude is that the sum of |M|2 over all possible final states is the probability for the scattering event. The normalization of the single-particle states must be chosen carefully, however, to ensure that M is a relativistic invariant.
Non-relativistic single particle states are labeled by the momentum k, and they are chosen to have the same norm at every value of k. This is because the nonrelativistic unit operator on single particle states is:
∫
d
k
|
k
⟩
⟨
k
|
.
{\displaystyle \int dk\,|k\rangle \langle k|\,.}
In relativity, the integral over the k-states for a particle of mass m integrates over a hyperbola in E,k space defined by the energy–momentum relation:
E
2
−
k
2
=
m
2
.
{\displaystyle E^{2}-k^{2}=m^{2}\,.}
If the integral weighs each k point equally, the measure is not Lorentz-invariant. The invariant measure integrates over all values of k and E, restricting to the hyperbola with a Lorentz-invariant delta function:
∫
δ
(
E
2
−
k
2
−
m
2
)
|
E
,
k
⟩
⟨
E
,
k
|
d
E
d
k
=
∫
d
k
2
E
|
k
⟩
⟨
k
|
.
{\displaystyle \int \delta (E^{2}-k^{2}-m^{2})|E,k\rangle \langle E,k|\,dE\,dk=\int {dk \over 2E}|k\rangle \langle k|\,.}
So the normalized k-states are different from the relativistically normalized k-states by a factor of
E
=
(
k
2
−
m
2
)
1
4
.
{\displaystyle {\sqrt {E}}=\left(k^{2}-m^{2}\right)^{\frac {1}{4}}\,.}
The invariant amplitude M is then the probability amplitude for relativistically normalized incoming states to become relativistically normalized outgoing states.
For nonrelativistic values of k, the relativistic normalization is the same as the nonrelativistic normalization (up to a constant factor √m). In this limit, the φ4 invariant scattering amplitude is still constant. The particles created by the field φ scatter in all directions with equal amplitude.
The nonrelativistic potential, which scatters in all directions with an equal amplitude (in the Born approximation), is one whose Fourier transform is constant—a delta-function potential. The lowest order scattering of the theory reveals the non-relativistic interpretation of this theory—it describes a collection of particles with a delta-function repulsion. Two such particles have an aversion to occupying the same point at the same time.
== Nonperturbative effects ==
Thinking of Feynman diagrams as a perturbation series, nonperturbative effects like tunneling do not show up, because any effect that goes to zero faster than any polynomial does not affect the Taylor series. Even bound states are absent, since at any finite order particles are only exchanged a finite number of times, and to make a bound state, the binding force must last forever.
But this point of view is misleading, because the diagrams not only describe scattering, but they also are a representation of the short-distance field theory correlations. They encode not only asymptotic processes like particle scattering, they also describe the multiplication rules for fields, the operator product expansion. Nonperturbative tunneling processes involve field configurations that on average get big when the coupling constant gets small, but each configuration is a coherent superposition of particles whose local interactions are described by Feynman diagrams. When the coupling is small, these become collective processes that involve large numbers of particles, but where the interactions between each of the particles is simple. (The perturbation series of any interacting quantum field theory has zero radius of convergence, complicating the limit of the infinite series of diagrams needed (in the limit of vanishing coupling) to describe such field configurations.)
This means that nonperturbative effects show up asymptotically in resummations of infinite classes of diagrams, and these diagrams can be locally simple. The graphs determine the local equations of motion, while the allowed large-scale configurations describe non-perturbative physics. But because Feynman propagators are nonlocal in time, translating a field process to a coherent particle language is not completely intuitive, and has only been explicitly worked out in certain special cases. In the case of nonrelativistic bound states, the Bethe–Salpeter equation describes the class of diagrams to include to describe a relativistic atom. For quantum chromodynamics, the Shifman–Vainshtein–Zakharov sum rules describe non-perturbatively excited long-wavelength field modes in particle language, but only in a phenomenological way.
The number of Feynman diagrams at high orders of perturbation theory is very large, because there are as many diagrams as there are graphs with a given number of nodes. Nonperturbative effects leave a signature on the way in which the number of diagrams and resummations diverge at high order. It is only because non-perturbative effects appear in hidden form in diagrams that it was possible to analyze nonperturbative effects in string theory, where in many cases a Feynman description is the only one available.
== In popular culture ==
The use of the above diagram of the virtual particle producing a quark–antiquark pair was featured in the television sit-com The Big Bang Theory, in the episode "The Bat Jar Conjecture".
PhD Comics of January 11, 2012, shows Feynman diagrams that visualize and describe quantum academic interactions, i.e. the paths followed by Ph.D. students when interacting with their advisors.
Vacuum Diagrams, a science fiction story by Stephen Baxter, features the titular vacuum diagram, a specific type of Feynman diagram.
Feynman and his wife, Gweneth Howarth, bought a Dodge Tradesman Maxivan in 1975, and had it painted with Feynman diagrams. The van is currently owned by video game designer and physicist Seamus Blackley. Qantum was the license plate ID.
== See also ==
== Notes ==
== References ==
== Sources ==
't Hooft, Gerardus; Veltman, Martinus (1973). "Diagrammar". CERN Yellow Report. doi:10.5170/CERN-1973-009. {{cite journal}}: Cite journal requires |journal= (help)
Kaiser, David (2005). Drawing Theories Apart: The Dispersion of Feynman Diagrams in Postwar Physics. Chicago, IL: University of Chicago Press. ISBN 0-226-42266-6.
Veltman, Martinus (1994-06-16). Diagrammatica: The Path to Feynman Diagrams. Cambridge Lecture Notes in Physics. ISBN 0-521-45692-4. (expanded, updated version of 't Hooft & Veltman, 1973, cited above)
Srednicki, Mark (2006). Quantum Field Theory. Script. Archived from the original on 2011-07-25. Retrieved 2011-01-28.
Schweber, S. S. (1994). QED and the men who made it: Dyson, Feynman, Schwinger, and Tomonaga. Princeton University Press. ISBN 978-0691033273.
== External links ==
AMS article: "What's New in Mathematics: Finite-dimensional Feynman Diagrams"
Draw Feynman diagrams explained by Flip Tanedo at Quantumdiaries.com
Drawing Feynman diagrams with FeynDiagram C++ library that produces PostScript output.
Online Diagram Tool A graphical application for creating publication ready diagrams.
JaxoDraw A Java program for drawing Feynman diagrams.
Bowley, Roger; Copeland, Ed (2010). "Feynman Diagrams". Sixty Symbols. Brady Haran for the University of Nottingham. | In theoretical physics, a Feynman diagram is a pictorial representation of the mathematical expressions describing the behavior and interaction of subatomic particles. The scheme is named after American physicist Richard Feynman, who introduced the diagrams in 1948. The interaction of subatomic particles can be complex and difficult to understand; Feynman diagrams give a simple visualization of what would otherwise be an arcane and abstract formula. According to David Kaiser, "Since the middle of the 20th century, theoretical physicists have increasingly turned to this tool to help them undertake critical calculations. Feynman diagrams have revolutionized nearly every aspect of theoretical physics." While the diagrams are applied primarily to quantum field theory, they can also be used in other areas of physics, such as solid-state theory. Frank Wilczek wrote that the calculations that won him the 2004 Nobel Prize in Physics "would have been literally unthinkable without Feynman diagrams, as would [Wilczek's] calculations that established a route to production and observation of the Higgs particle."
Feynman used Ernst Stueckelberg's interpretation of the positron as if it were an electron moving backward in time. Thus, antiparticles are represented as moving backward along the time axis in Feynman diagrams.
The calculation of probability amplitudes in theoretical particle physics requires the use of rather large and complicated integrals over a large number of variables. Feynman diagrams can represent these integrals graphically.
A Feynman diagram is a graphical representation of a perturbative contribution to the transition amplitude or correlation function of a quantum mechanical or statistical field theory. Within the canonical formulation of quantum field theory, a Feynman diagram represents a term in the Wick's expansion of the perturbative S-matrix. Alternatively, the path integral formulation of quantum field theory represents the transition amplitude as a weighted sum of all possible histories of the system from the initial to the final state, in terms of either particles or fields. The transition amplitude is then given as the matrix element of the S-matrix between the initial and final states of the quantum system. | 14 |
374 | ornithology | Ornithologie (wiktionary) | ornitho- + -logie
Ornithologie f (genitive Ornithologie, no plural)
ornithology (scientific study of birds)
Synonym: Vogelkunde
“Ornithologie” in Duden online
“Ornithologie” in Digitales Wörterbuch der deutschen Sprache | ornitho- + -logie
Ornithologie f (genitive Ornithologie, no plural)
ornithology (scientific study of birds)
Synonym: Vogelkunde
“Ornithologie” in Duden online
“Ornithologie” in Digitales Wörterbuch der deutschen Sprache | 4 |
375 | ornithology | ornithologie (wiktionary) | From ornithologue + -ie.
IPA(key): /ɔʁ.ni.tɔ.lɔ.ʒi/
ornithologie f (plural ornithologies)
ornithology
ornithologique
ornithologue
→ Turkish: ornitoloji
“ornithologie”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012. | From ornithologue + -ie.
IPA(key): /ɔʁ.ni.tɔ.lɔ.ʒi/
ornithologie f (plural ornithologies)
ornithology
ornithologique
ornithologue
→ Turkish: ornitoloji
“ornithologie”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012. | 5 |
376 | ornithology | ornithology (wiktionary) | From New Latin ornithologia, coined by Ulisse Aldrovandi from Ancient Greek ὀρνιθολόγος (ornithológos), from ὄρνις (órnis) and λόγος (lógos). See also ornitho- + -logy.
Rhymes: -ɒlədʒi
ornithology (countable and uncountable, plural ornithologies)
The branch of zoology that deals with the scientific study of birds.
Synonyms: birdlore, fowl-lore | From New Latin ornithologia, coined by Ulisse Aldrovandi from Ancient Greek ὀρνιθολόγος (ornithológos), from ὄρνις (órnis) and λόγος (lógos). See also ornitho- + -logy.
Rhymes: -ɒlədʒi
ornithology (countable and uncountable, plural ornithologies)
The branch of zoology that deals with the scientific study of birds.
Synonyms: birdlore, fowl-lore | 5 |
377 | ornithology | Ornithology (wikipedia) | Ornithology is a branch of zoology that concerns the study of birds. Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds. It has also been an area with a large contribution made by amateurs in terms of time, resources, and financial support. Studies on birds have helped develop key concepts in biology including evolution, behaviour and ecology such as the definition of species, the process of speciation, instinct, learning, ecological niches, guilds, island biogeography, phylogeography, and conservation.
While early ornithology was principally concerned with descriptions and distributions of species, ornithologists today seek answers to very specific questions, often using birds as models to test hypotheses or predictions based on theories. Most modern biological theories apply across life forms, and the number of scientists who identify themselves as "ornithologists" has therefore declined. A wide range of tools and techniques are used in ornithology, both inside the laboratory and out in the field, and innovations are constantly made. Most biologists who recognise themselves as "ornithologists" study specific biology research areas, such as anatomy, physiology, taxonomy, ecology, or behaviour.
== Definition and etymology ==
The word "ornithology" comes from the late 16th-century Latin ornithologia meaning "bird science" from the Greek ὄρνις ornis ("bird") and λόγος logos ("theory, science, thought").
== History ==
The history of ornithology largely reflects the trends in the history of biology, as well as many other scientific disciplines, including ecology, anatomy, physiology, paleontology, and more recently, molecular biology. Trends include the move from mere descriptions to the identification of patterns, thus towards elucidating the processes that produce these patterns.
=== Early knowledge and study ===
Humans have had an observational relationship with birds since prehistory, with some stone-age drawings being amongst the oldest indications of an interest in birds. Birds were perhaps important as food sources, and bones of as many as 80 species have been found in excavations of early Stone Age settlements. Waterbird and seabird remains have also been found in shell mounds on the island of Oronsay off the coast of Scotland.
Cultures around the world have rich vocabularies related to birds. Traditional bird names are often based on detailed knowledge of the behaviour, with many names being onomatopoeic, and still in use. Traditional knowledge may also involve the use of birds in folk medicine and knowledge of these practices are passed on through oral traditions (see ethno-ornithology). Hunting of wild birds as well as their domestication would have required considerable knowledge of their habits. Poultry farming and falconry were practised from early times in many parts of the world. Artificial incubation of poultry was practised in China around 246 BC and around at least 400 BC in Egypt. The Egyptians also made use of birds in their hieroglyphic scripts, many of which, though stylized, are still identifiable to species. Early written records provide valuable information on the past distributions of species. For instance, Xenophon records the abundance of the ostrich in Assyria (Anabasis, i. 5); this subspecies from Asia Minor is extinct and all extant ostrich races are today restricted to Africa. Other old writings such as the Vedas (1500–800 BC) demonstrate the careful observation of avian life histories and include the earliest reference to the habit of brood parasitism by the Asian koel (Eudynamys scolopaceus). Like writing, the early art of China, Japan, Persia, and India also demonstrate knowledge, with examples of scientifically accurate bird illustrations.
Aristotle in 350 BC in his History of animals noted the habit of bird migration, moulting, egg laying, and lifespans, as well as compiling a list of 170 different bird species. However, he also introduced and propagated several myths, such as the idea that swallows hibernated in winter, although he noted that cranes migrated from the steppes of Scythia to the marshes at the headwaters of the Nile. The idea of swallow hibernation became so well established that even as late as in 1878, Elliott Coues could list as many as 182 contemporary publications dealing with the hibernation of swallows and little published evidence to contradict the theory. Similar misconceptions existed regarding the breeding of barnacle geese. Their nests had not been seen, and they were believed to grow by transformations of goose barnacles, an idea that became prevalent from around the 11th century and noted by Bishop Giraldus Cambrensis (Gerald of Wales) in Topographia Hiberniae (1187). Around 77 AD, Pliny the Elder described birds, among other creatures, in his Historia Naturalis.
The earliest record of falconry comes from the reign of Sargon II (722–705 BC) in Assyria. Falconry is thought to have made its entry to Europe only after AD 400, brought in from the east after invasions by the Huns and Alans. Starting from the eighth century, numerous Arabic works on the subject and general ornithology were written, as well as translations of the works of ancient writers from Greek and Syriac. In the 12th and 13th centuries, crusades and conquest had subjugated Islamic territories in southern Italy, central Spain, and the Levant under European rule, and for the first time translations into Latin of the great works of Arabic and Greek scholars were made with the help of Jewish and Muslim scholars, especially in Toledo, which had fallen into Christian hands in 1085 and whose libraries had escaped destruction. Michael Scotus from Scotland made a Latin translation of Aristotle's work on animals from Arabic here around 1215, which was disseminated widely and was the first time in a millennium that this foundational text on zoology became available to Europeans. Falconry was popular in the Norman court in Sicily, and a number of works on the subject were written in Palermo. Emperor Frederick II of Hohenstaufen (1194–1250) learned about an falconry during his youth in Sicily and later built up a menagerie and sponsored translations of Arabic texts, among which the popular Arabic work known as the Liber Moaminus by an unknown author which was translated into Latin by Theodore of Antioch from Syria in 1240-1241 as the De Scientia Venandi per Aves, and also Michael Scotus (who had removed to Palermo) translated Ibn Sīnā's Kitāb al-Ḥayawān of 1027 for the Emperor, a commentary and scientific update of Aristotle's work which was part of Ibn Sīnā's massive Kitāb al-Šifāʾ. Frederick II eventually wrote his own treatise on falconry, the De arte venandi cum avibus, in which he related his ornithological observations and the results of the hunts and experiments his court enjoyed performing.
Several early German and French scholars compiled old works and conducted new research on birds. These included Guillaume Rondelet, who described his observations in the Mediterranean, and Pierre Belon, who described the fish and birds that he had seen in France and the Levant. Belon's Book of Birds (1555) is a folio volume with descriptions of some 200 species. His comparison of the skeleton of humans and birds is considered as a landmark in comparative anatomy. Volcher Coiter (1534–1576), a Dutch anatomist, made detailed studies of the internal structures of birds and produced a classification of birds, De Differentiis Avium (around 1572), that was based on structure and habits. Konrad Gesner wrote the Vogelbuch and Icones avium omnium around 1557. Like Gesner, Ulisse Aldrovandi, an encyclopedic naturalist, began a 14-volume natural history with three volumes on birds, entitled ornithologiae hoc est de avibus historiae libri XII, which was published from 1599 to 1603. Aldrovandi showed great interest in plants and animals, and his work included 3000 drawings of fruits, flowers, plants, and animals, published in 363 volumes. His Ornithology alone covers 2000 pages and included such aspects as the chicken and poultry techniques. He used a number of traits including behaviour, particularly bathing and dusting, to classify bird groups.
William Turner's Historia Avium (History of Birds), published at Cologne in 1544, was an early ornithological work from England. He noted the commonness of kites in English cities where they snatched food out of the hands of children. He included folk beliefs such as those of anglers. Anglers believed that the osprey emptied their fishponds and would kill them, mixing the flesh of the osprey into their fish bait. Turner's work reflected the violent times in which he lived, and stands in contrast to later works such as Gilbert White's 1789 The Natural History and Antiquities of Selborne that were written in a tranquil era.
In the 17th century, Francis Willughby (1635–1672) and John Ray (1627–1705) created the first major system of bird classification that was based on function and morphology rather than on form or behaviour. Willughby's Ornithologiae libri tres (1676) completed by John Ray is sometimes considered to mark the beginning of scientific ornithology. Ray also worked on Ornithologia, which was published posthumously in 1713 as Synopsis methodica avium et piscium. The earliest list of British birds, Pinax Rerum Naturalium Britannicarum, was written by Christopher Merrett in 1667, but authors such as John Ray considered it of little value. Ray did, however, value the expertise of the naturalist Sir Thomas Browne (1605–82), who not only answered his queries on ornithological identification and nomenclature, but also those of Willoughby and Merrett in letter correspondence. Browne himself in his lifetime kept an eagle, owl, cormorant, bittern, and ostrich, penned a tract on falconry, and introduced the words "incubation" and "oviparous" into the English language.
Towards the late 18th century, Mathurin Jacques Brisson (1723–1806) and Comte de Buffon (1707–1788) began new works on birds. Brisson produced a six-volume work Ornithologie in 1760 and Buffon's included nine volumes (volumes 16–24) on birds Histoire naturelle des oiseaux (1770–1785) in his work on science Histoire naturelle générale et particulière (1749–1804). Jacob Temminck sponsored François Le Vaillant [1753–1824] to collect bird specimens in Southern Africa and Le Vaillant's six-volume Histoire naturelle des oiseaux d'Afrique (1796–1808) included many non-African birds. His other bird books produced in collaboration with the artist Barraband are considered among the most valuable illustrated guides ever produced. Louis Pierre Vieillot (1748–1831) spent 10 years studying North American birds and wrote the Histoire naturelle des oiseaux de l'Amerique septentrionale (1807–1808?). Vieillot pioneered in the use of life histories and habits in classification. Alexander Wilson composed a nine-volume work, American Ornithology, published 1808-1814, which is the first such record of North American birds, significantly antedating Audubon. In the early 19th century, Lewis and Clark studied and identified many birds in the western United States. John James Audubon, born in 1785, observed and painted birds in France and later in the Ohio and Mississippi valleys. From 1827 to 1838, Audubon published The Birds of America, which was engraved by Robert Havell Sr. and his son Robert Havell Jr. Containing 435 engravings, it is often regarded as the greatest ornithological work in history.
=== Scientific studies ===
The emergence of ornithology as a scientific discipline began in the 18th century, when Mark Catesby published his two-volume Natural History of Carolina, Florida, and the Bahama Islands, a landmark work which included 220 hand-painted engravings and was the basis for many of the species Carl Linnaeus described in the 1758 Systema Naturae. Linnaeus' work revolutionised bird taxonomy by assigning every species a binomial name, categorising them into different genera. However, ornithology did not emerge as a specialised science until the Victorian era—with the popularization of natural history, and the collection of natural objects such as bird eggs and skins. This specialization led to the formation in Britain of the British Ornithologists' Union in 1858. In 1859, the members founded its journal The Ibis. The sudden spurt in ornithology was also due in part to colonialism. At 100 years later, in 1959, R. E. Moreau noted that ornithology in this period was preoccupied with the geographical distributions of various species of birds.
No doubt the preoccupation with widely extended geographical ornithology, was fostered by the immensity of the areas over which British rule or influence stretched during the 19th century and for some time afterwards.
The bird collectors of the Victorian era observed the variations in bird forms and habits across geographic regions, noting local specialization and variation in widespread species. The collections of museums and private collectors grew with contributions from various parts of the world. The naming of species with binomials and the organization of birds into groups based on their similarities became the main work of museum specialists. The variations in widespread birds across geographical regions caused the introduction of trinomial names.
The search for patterns in the variations of birds was attempted by many. Friedrich Wilhelm Joseph Schelling (1775–1854), his student Johann Baptist von Spix (1781–1826), and several others believed that a hidden and innate mathematical order existed in the forms of birds. They believed that a "natural" classification was available and superior to "artificial" ones. A particularly popular idea was the Quinarian system popularised by Nicholas Aylward Vigors (1785–1840), William Sharp Macleay (1792–1865), William Swainson, and others. The idea was that nature followed a "rule of five" with five groups nested hierarchically. Some had attempted a rule of four, but Johann Jakob Kaup (1803–1873) insisted that the number five was special, noting that other natural entities such as the senses also came in fives. He followed this idea and demonstrated his view of the order within the crow family. Where he failed to find five genera, he left a blank insisting that a new genus would be found to fill these gaps. These ideas were replaced by more complex "maps" of affinities in works by Hugh Edwin Strickland and Alfred Russel Wallace. A major advance was made by Max Fürbringer in 1888, who established a comprehensive phylogeny of birds based on anatomy, morphology, distribution, and biology. This was developed further by Hans Gadow and others.
The Galapagos finches were especially influential in the development of Charles Darwin's theory of evolution. His contemporary Alfred Russel Wallace also noted these variations and the geographical separations between different forms leading to the study of biogeography. Wallace was influenced by the work of Philip Lutley Sclater on the distribution patterns of birds.
For Darwin, the problem was how species arose from a common ancestor, but he did not attempt to find rules for delineation of species. The species problem was tackled by the ornithologist Ernst Mayr, who was able to demonstrate that geographical isolation and the accumulation of genetic differences led to the splitting of species.
Early ornithologists were preoccupied with matters of species identification. Only systematics counted as true science and field studies were considered inferior through much of the 19th century. In 1901, Robert Ridgway wrote in the introduction to The Birds of North and Middle America that:
There are two essentially different kinds of ornithology: systematic or scientific, and popular. The former deals with the structure and classification of birds, their synonymies, and technical descriptions. The latter treats of their habits, songs, nesting, and other facts pertaining to their life histories.
This early idea that the study of living birds was merely recreation held sway until ecological theories became the predominant focus of ornithological studies. The study of birds in their habitats was particularly advanced in Germany with bird ringing stations established as early as 1903. By the 1920s, the Journal für Ornithologie included many papers on the behaviour, ecology, anatomy, and physiology, many written by Erwin Stresemann. Stresemann changed the editorial policy of the journal, leading both to a unification of field and laboratory studies and a shift of research from museums to universities. Ornithology in the United States continued to be dominated by museum studies of morphological variations, species identities, and geographic distributions, until it was influenced by Stresemann's student Ernst Mayr. In Britain, some of the earliest ornithological works that used the word ecology appeared in 1915. The Ibis, however, resisted the introduction of these new methods of study, and no paper on ecology appeared until 1943. The work of David Lack on population ecology was pioneering. Newer quantitative approaches were introduced for the study of ecology and behaviour, and this was not readily accepted. For instance, Claud Ticehurst wrote:
Sometimes it seems that elaborate plans and statistics are made to prove what is commonplace knowledge to the mere collector, such as that hunting parties often travel more or less in circles.
David Lack's studies on population ecology sought to find the processes involved in the regulation of population based on the evolution of optimal clutch sizes. He concluded that population was regulated primarily by density-dependent controls, and also suggested that natural selection produces life-history traits that maximize the fitness of individuals. Others, such as Wynne-Edwards, interpreted population regulation as a mechanism that aided the "species" rather than individuals. This led to widespread and sometimes bitter debate on what constituted the "unit of selection". Lack also pioneered the use of many new tools for ornithological research, including the idea of using radar to study bird migration.
Birds were also widely used in studies of the niche hypothesis and Georgii Gause's competitive exclusion principle. Work on resource partitioning and the structuring of bird communities through competition were made by Robert MacArthur. Patterns of biodiversity also became a topic of interest. Work on the relationship of the number of species to area and its application in the study of island biogeography was pioneered by E. O. Wilson and Robert MacArthur. These studies led to the development of the discipline of landscape ecology.
John Hurrell Crook studied the behaviour of weaverbirds and demonstrated the links between ecological conditions, behaviour, and social systems. Principles from economics were introduced to the study of biology by Jerram L. Brown in his work on explaining territorial behaviour. This led to more studies of behaviour that made use of cost-benefit analyses. The rising interest in sociobiology also led to a spurt of bird studies in this area.
The study of imprinting behaviour in ducks and geese by Konrad Lorenz and the studies of instinct in herring gulls by Nicolaas Tinbergen led to the establishment of the field of ethology. The study of learning became an area of interest and the study of bird songs has been a model for studies in neuroethology. The study of hormones and physiology in the control of behaviour has also been aided by bird models. These have helped in finding the proximate causes of circadian and seasonal cycles. Studies on migration have attempted to answer questions on the evolution of migration, orientation, and navigation.
The growth of genetics and the rise of molecular biology led to the application of the gene-centered view of evolution to explain avian phenomena. Studies on kinship and altruism, such as helpers, became of particular interest. The idea of inclusive fitness was used to interpret observations on behaviour and life history, and birds were widely used models for testing hypotheses based on theories postulated by W. D. Hamilton and others.
The new tools of molecular biology changed the study of bird systematics, which changed from being based on phenotype to the underlying genotype. The use of techniques such as DNA-DNA hybridization to study evolutionary relationships was pioneered by Charles Sibley and Jon Edward Ahlquist, resulting in what is called the Sibley-Ahlquist taxonomy. These early techniques have been replaced by newer ones based on mitochondrial DNA sequences and molecular phylogenetics approaches that make use of computational procedures for sequence alignment, construction of phylogenetic trees, and calibration of molecular clocks to infer evolutionary relationships. Molecular techniques are also widely used in studies of avian population biology and ecology.
=== Rise to popularity ===
The use of field glasses or telescopes for bird observation began in the 1820s and 1830s, with pioneers such as J. Dovaston (who also pioneered in the use of bird feeders), but instruction manuals did not begin to insist on the use of optical aids such as "a first-class telescope" or "field glass" until the 1880s.
The rise of field guides for the identification of birds was another major innovation. The early guides such as Thomas Bewick's two-volume guide and William Yarrell's three-volume guide were cumbersome, and mainly focused on identifying specimens in the hand. The earliest of the new generation of field guides was prepared by Florence Merriam, sister of Clinton Hart Merriam, the mammalogist. This was published in 1887 in a series Hints to Audubon Workers: Fifty Birds and How to Know Them in Grinnell's Audubon Magazine. These were followed by new field guides,
from the pioneering illustrated handbooks of Frank Chapman to the classic Field Guide to the Birds by Roger Tory Peterson in 1934, to Birds of the West Indies published in 1936 by Dr. James Bond - the same who inspired the amateur ornithologist Ian Fleming in naming his famous literary spy.
The interest in birdwatching grew in popularity in many parts of the world, and the possibility for amateurs to contribute to biological studies was soon realized. As early as 1916, Julian Huxley wrote a two-part article in The Auk, noting the tensions between amateurs and professionals, and suggested the possibility that the "vast army of bird lovers and bird watchers could begin providing the data scientists needed to address the fundamental problems of biology." The amateur ornithologist Harold F. Mayfield noted that the field was also funded by non-professionals. He noted that in 1975, 12% of the papers in American ornithology journals were written by persons who were not employed in biology related work.
Organizations were started in many countries, and these grew rapidly in membership, most notable among them being the Royal Society for the Protection of Birds (RSPB) in Britain and the Audubon Society in the US, which started in 1885. Both these organizations were started with the primary objective of conservation. The RSPB, born in 1889, grew from a small Croydon-based group of women, including Eliza Phillips, Etta Lemon, Catherine Hall and Hannah Poland. Calling themselves the "Fur, Fin, and Feather Folk", the group met regularly and took a pledge "to refrain from wearing the feathers of any birds not killed for the purpose of food, the ostrich only exempted." The organization did not allow men as members initially, avenging a policy of the British Ornithologists' Union to keep out women. Unlike the RSPB, which was primarily conservation oriented, the British Trust for Ornithology was started in 1933 with the aim of advancing ornithological research. Members were often involved in collaborative ornithological projects. These projects have resulted in atlases which detail the distribution of bird species across Britain. In Canada, citizen scientist Elsie Cassels studied migratory birds and was involved in establishing Gaetz Lakes bird sanctuary. In the United States, the Breeding Bird Surveys, conducted by the United States Geological Survey, have also produced atlases with information on breeding densities and changes in the density and distribution over time. Other volunteer collaborative ornithology projects were subsequently established in other parts of the world.
== Techniques ==
The tools and techniques of ornithology are varied, and new inventions and approaches are quickly incorporated. The techniques may be broadly dealt under the categories of those that are applicable to specimens and those that are used in the field, but the classification is rough and many analysis techniques are usable both in the laboratory and field or may require a combination of field and laboratory techniques.
=== Collections ===
The earliest approaches to modern bird study involved the collection of eggs, a practice known as oology. While collecting became a pastime for many amateurs, the labels associated with these early egg collections made them unreliable for the serious study of bird breeding. To preserve eggs, a tiny hole was made and the contents extracted. This technique became standard with the invention of the blow drill around 1830. Egg collection is no longer popular; however, historic museum collections have been of value in determining the effects of pesticides such as DDT on physiology. Museum bird collections continue to act as a resource for taxonomic studies.
The use of bird skins to document species has been a standard part of systematic ornithology. Bird skins are prepared by retaining the key bones of the wings, legs, and skull along with the skin and feathers. In the past, they were treated with arsenic to prevent fungal and insect (mostly dermestid) attack. Arsenic, being toxic, was replaced by less-toxic borax. Amateur and professional collectors became familiar with these skinning techniques and started sending in their skins to museums, some of them from distant locations. This led to the formation of huge collections of bird skins in museums in Europe and North America. Many private collections were also formed. These became references for comparison of species, and the ornithologists at these museums were able to compare species from different locations, often places that they themselves never visited. Morphometrics of these skins, particularly the lengths of the tarsus, bill, tail, and wing became important in the descriptions of bird species. These skin collections have been used in more recent times for studies on molecular phylogenetics by the extraction of ancient DNA. The importance of type specimens in the description of species make skin collections a vital resource for systematic ornithology. However, with the rise of molecular techniques, establishing the taxonomic status of new discoveries, such as the Bulo Burti boubou (Laniarius liberatus, no longer a valid species) and the Bugun liocichla (Liocichla bugunorum), using blood, DNA and feather samples as the holotype material, has now become possible.
Other methods of preservation include the storage of specimens in spirit. Such wet specimens have special value in physiological and anatomical study, apart from providing better quality of DNA for molecular studies. Freeze drying of specimens is another technique that has the advantage of preserving stomach contents and anatomy, although it tends to shrink, making it less reliable for morphometrics.
=== In the field ===
The study of birds in the field was helped enormously by improvements in optics. Photography made it possible to document birds in the field with great accuracy. High-power spotting scopes today allow observers to detect minute morphological differences that were earlier possible only by examination of the specimen "in the hand".
The capture and marking of birds enable detailed studies of life history. Techniques for capturing birds are varied and include the use of bird liming for perching birds, mist nets for woodland birds, cannon netting for open-area flocking birds, the bal-chatri trap for raptors, decoys and funnel traps for water birds.
The bird in the hand may be examined and measurements can be made, including standard lengths and weights. Feather moult and skull ossification provide indications of age and health. Sex can be determined by examination of anatomy in some sexually nondimorphic species. Blood samples may be drawn to determine hormonal conditions in studies of physiology, identify DNA markers for studying genetics and kinship in studies of breeding biology and phylogeography. Blood may also be used to identify pathogens and arthropod-borne viruses. Ectoparasites may be collected for studies of coevolution and zoonoses. In many cryptic species, measurements (such as the relative lengths of wing feathers in warblers) are vital in establishing identity. Captured birds are often marked for future recognition. Rings or bands provide long-lasting identification, but require capture for the information on them to be read. Field-identifiable marks such as coloured bands, wing tags, or dyes enable short-term studies where individual identification is required. Mark and recapture techniques make demographic studies possible. Ringing has traditionally been used in the study of migration. In recent times, satellite transmitters provide the ability to track migrating birds in near-real time.
Techniques for estimating population density include point counts, transects, and territory mapping. Observations are made in the field using carefully designed protocols and the data may be analysed to estimate bird diversity, relative abundance, or absolute population densities. These methods may be used repeatedly over large timespans to monitor changes in the environment. Camera traps have been found to be a useful tool for the detection and documentation of elusive species, nest predators and in the quantitative analysis of frugivory, seed dispersal and behaviour.
=== In the laboratory ===
Many aspects of bird biology are difficult to study in the field. These include the study of behavioural and physiological changes that require a long duration of access to the bird. Nondestructive samples of blood or feathers taken during field studies may be studied in the laboratory. For instance, the variation in the ratios of stable hydrogen isotopes across latitudes makes establishing the origins of migrant birds possible using mass spectrometric analysis of feather samples. These techniques can be used in combination with other techniques such as ringing.
The first attenuated vaccine developed by Louis Pasteur, for fowl cholera, was tested on poultry in 1878. Anti-malarials were tested on birds which harbour avian-malarias. Poultry continues to be used as a model for many studies in non-mammalian immunology.
Studies in bird behaviour include the use of tamed and trained birds in captivity. Studies on bird intelligence and song learning have been largely laboratory-based. Field researchers may make use of a wide range of techniques such as the use of dummy owls to elicit mobbing behaviour, and dummy males or the use of call playback to elicit territorial behaviour and thereby to establish the boundaries of bird territories. Studies of bird migration including aspects of navigation, orientation, and physiology are often studied using captive birds in special cages that record their activities. The Emlen funnel, for instance, makes use of a cage with an inkpad at the centre and a conical floor where the ink marks can be counted to identify the direction in which the bird attempts to fly. The funnel can have a transparent top and visible cues such as the direction of sunlight may be controlled using mirrors or the positions of the stars simulated in a planetarium.
The entire genome of the domestic fowl (Gallus gallus) was sequenced in 2004, and was followed in 2008 by the genome of the zebra finch (Taeniopygia guttata). Such whole-genome sequencing projects allow for studies on evolutionary processes involved in speciation. Associations between the expression of genes and behaviour may be studied using candidate genes. Variations in the exploratory behaviour of great tits (Parus major) have been found to be linked with a gene orthologous to the human gene DRD4 (Dopamine receptor D4) which is known to be associated with novelty-seeking behaviour. The role of gene expression in developmental differences and morphological variations have been studied in Darwin's finches. The difference in the expression of Bmp4 have been shown to be associated with changes in the growth and shape of the beak.
The chicken has long been a model organism for studying vertebrate developmental biology. As the embryo is readily accessible, its development can be easily followed (unlike mice). This also allows the use of electroporation for studying the effect of adding or silencing a gene. Other tools for perturbing their genetic makeup are chicken embryonic stem cells and viral vectors.
=== Collaborative studies ===
With the widespread interest in birds, use of a large number of people to work on collaborative ornithological projects that cover large geographic scales has been possible. These citizen science projects include nationwide projects such as the Christmas Bird Count, Backyard Bird Count, the North American Breeding Bird Survey, the Canadian EPOQ or regional projects such as the Asian Waterfowl Census and Spring Alive in Europe. These projects help to identify distributions of birds, their population densities and changes over time, arrival and departure dates of migration, breeding seasonality, and even population genetics. The results of many of these projects are published as bird atlases. Studies of migration using bird ringing or colour marking often involve the cooperation of people and organizations in different countries.
== Applications ==
Wild birds impact many human activities, while domesticated birds are important sources of eggs, meat, feathers, and other products. Applied and economic ornithology aim to reduce the ill effects of problem birds and enhance gains from beneficial species.
The role of some species of birds as pests has been well known, particularly in agriculture. Granivorous birds such as the queleas in Africa are among the most numerous birds in the world, and foraging flocks can cause devastation. Many insectivorous birds are also noted as beneficial in agriculture. Many early studies on the benefits or damages caused by birds in fields were made by analysis of stomach contents and observation of feeding behaviour. Modern studies aimed to manage birds in agriculture make use of a wide range of principles from ecology. Intensive aquaculture has brought humans in conflict with fish-eating birds such as cormorants.
Large flocks of pigeons and starlings in cities are often considered as a nuisance, and techniques to reduce their populations or their impacts are constantly innovated. Birds are also of medical importance, and their role as carriers of human diseases such as Japanese encephalitis, West Nile virus, and influenza H5N1 have been widely recognized. Bird strikes and the damage they cause in aviation are of particularly great importance, due to the fatal consequences and the level of economic losses caused. The airline industry incurs worldwide damages of an estimated US$1.2 billion each year.
Many species of birds have been driven to extinction by human activities. Being conspicuous elements of the ecosystem, they have been considered as indicators of ecological health. They have also helped in gathering support for habitat conservation. Bird conservation requires specialized knowledge in aspects of biology and ecology, and may require the use of very location-specific approaches. Ornithologists contribute to conservation biology by studying the ecology of birds in the wild and identifying the key threats and ways of enhancing the survival of species. Critically endangered species such as the California condor have had to be captured and bred in captivity. Such ex situ conservation measures may be followed by reintroduction of the species into the wild.
== See also ==
== References ==
== Additional sources ==
Birkhead T, Wimpenny J; Montgomerie B (2014). Ten Thousand Birds: Ornithology since Darwin. Princeton University Press. ISBN 9780691151977.
Chansigaud, Valerie (2009). History of Ornithology. London: New Holland Publishers. ISBN 978-1-84773-433-4.
Gurney, John Henry (1921). "Early annals of ornithology". Nature. 108 (2713): 268. Bibcode:1921Natur.108..268.. doi:10.1038/108268a0. hdl:2027/coo.31924090299532. S2CID 4033666. Retrieved 19 November 2010.
Newton, Alfred (1884). Ornithology. [S.l. : s.n.(Reprinted from the 1884 Encyclopædia Britannica)
Podulka, Sandy; Eckhardt, Marie; Otis, Daniel (2001). "Birds and Humans: A Historical Perspective". In Podulka, Sandy; Rohrbaugh, Ronald W.; Bonney, Rick (eds.). Handbook of Bird Biology (2nd ed.). Ithaca, NY: Cornell Lab of Ornithology. pp. H1–H42. ISBN 978-0-938027-62-1.
Walters, Michael (2005). A Concise History of Ornithology. New Haven, CT: Yale University Press. ISBN 978-1-84773-433-4.
== External links ==
Lewis, Daniel. The Feathery Tribe: Robert Ridgway and the Modern Study of Birds. Yale University Press. [1].
Ornithologie (1773–1792) Francois Nicholas Martinet Digital Edition Smithsonian Digital Libraries
"West Midland Bird Club: Older Organisations". Archived from the original on May 9, 2013. Retrieved May 23, 2004.{{cite web}}: CS1 maint: unfit URL (link)
History of ornithology in North America
History of ornithology and ornithology collections in Victoria, Australia on Culture Victoria
History of ornithology in China
Hill ornithology collections | Ornithology is a branch of zoology that concerns the study of birds. Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds. It has also been an area with a large contribution made by amateurs in terms of time, resources, and financial support. Studies on birds have helped develop key concepts in biology including evolution, behaviour and ecology such as the definition of species, the process of speciation, instinct, learning, ecological niches, guilds, island biogeography, phylogeography, and conservation.
While early ornithology was principally concerned with descriptions and distributions of species, ornithologists today seek answers to very specific questions, often using birds as models to test hypotheses or predictions based on theories. Most modern biological theories apply across life forms, and the number of scientists who identify themselves as "ornithologists" has therefore declined. A wide range of tools and techniques are used in ornithology, both inside the laboratory and out in the field, and innovations are constantly made. Most biologists who recognise themselves as "ornithologists" study specific biology research areas, such as anatomy, physiology, taxonomy, ecology, or behaviour. | 7 |
378 | ornithology | Ornithology (composition) (wikipedia) | "Ornithology" is a jazz standard by bebop alto saxophonist Charlie Parker and trumpeter Benny Harris.
== Description ==
Its title is a reference to Parker's nickname, "Bird" (ornithology is the study of birds). The Charlie Parker Septet made the first recording of the tune on March 28, 1946 on the Dial label, and it was inducted into the Grammy Hall of Fame in 1989.
"Ornithology" is a contrafact – a newly created melody written over the chord progression of another song, in this case the standard "How High the Moon". It remains one of the most popular and frequently performed bebop tunes. Jazz vocalists scatting on "How High the Moon" (notably Ella Fitzgerald) often quote the melody of "Ornithology" (and vice versa). Coleman Hawkins used the first two bars of the melody in a Cozy Cole recording session dating back to November 14, 1944, in a tune called "Look Here".
Notable recordings include Bud Powell's version and the Gerry Mulligan-Chet Baker 1957 version. Babs Gonzales wrote vocalese lyrics for the tune.
"Ornithology" was prominently featured in the novel Suder by Percival Everett.
The name was also used by a jazz club in Brooklyn, Ornithology Jazz Club.
== See also ==
List of jazz contrafacts
== Footnotes == | "Ornithology" is a jazz standard by bebop alto saxophonist Charlie Parker and trumpeter Benny Harris.
| 0 |
379 | ornithology | Ornithology (journal) (wikipedia) | Ornithology, formerly The Auk and The Auk: Ornithological Advances, is a peer-reviewed scientific journal and the official publication of the American Ornithological Society (AOS). It was established in 1884 and is published quarterly. The journal covers the anatomy, behavior, and distribution of birds. It was named for the great auk, the symbol of the AOS.
In 2018, the American Ornithology Society announced a partnership with Oxford University Press to publish The Auk: Ornithological Advances and The Condor: Ornithological Applications.
In January 2021, the journal was renamed Ornithology, with the stated goal of improving descriptiveness, thematic focus, and ease of citation of the journal title. The society's sister publication The Condor was renamed Ornithological Applications at the same time.
== Editors ==
The following have been editors-in-chief of the journal:
== See also ==
List of ornithology journals
== References ==
== External links ==
Official website
BioOne: Ornithology. Vol. 117 (2000) onwards; free HTML abstracts, subscription required for PDF full text.
SORA: The Auk. Vol. 1–118 (1884–2001) free PDF/DejaVu full text.
Vol. 1–37 (1884–1920) in Biodiversity Heritage Library | Ornithology, formerly The Auk and The Auk: Ornithological Advances, is a peer-reviewed scientific journal and the official publication of the American Ornithological Society (AOS). It was established in 1884 and is published quarterly. The journal covers the anatomy, behavior, and distribution of birds. It was named for the great auk, the symbol of the AOS.
In 2018, the American Ornithology Society announced a partnership with Oxford University Press to publish The Auk: Ornithological Advances and The Condor: Ornithological Applications.
In January 2021, the journal was renamed Ornithology, with the stated goal of improving descriptiveness, thematic focus, and ease of citation of the journal title. The society's sister publication The Condor was renamed Ornithological Applications at the same time.
| 6 |
380 | primary tuberculosis | Tuberculosis (wikipedia) | Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is an infectious disease usually caused by Mycobacterium tuberculosis (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in which case it is known as latent tuberculosis. Around 10% of latent infections progress to active disease which, if left untreated, kill about half of those affected. Typical symptoms of active TB are chronic cough with blood-containing mucus, fever, night sweats, and weight loss. Infection of other organs can cause a wide range of symptoms.
Tuberculosis is spread from one person to the next through the air when people who have active TB in their lungs cough, spit, speak, or sneeze. People with latent TB do not spread the disease. Active infection occurs more often in people with HIV/AIDS and in those who smoke. Diagnosis of active TB is based on chest X-rays, as well as microscopic examination and culture of body fluids. Diagnosis of latent TB relies on the tuberculin skin test (TST) or blood tests.
Prevention of TB involves screening those at high risk, early detection and treatment of cases, and vaccination with the bacillus Calmette-Guérin (BCG) vaccine. Those at high risk include household, workplace, and social contacts of people with active TB. Treatment requires the use of multiple antibiotics over a long period of time. Antibiotic resistance is a growing problem, with increasing rates of multiple drug-resistant tuberculosis (MDR-TB).
In 2018, one quarter of the world's population was thought to have a latent infection of TB. New infections occur in about 1% of the population each year. In 2022, an estimated 10.6 million people developed active TB, resulting in 1.3 million deaths, making it the second leading cause of death from an infectious disease after COVID-19. As of 2018, most TB cases occurred in the regions of South-East Asia (44%), Africa (24%), and the Western Pacific (18%), with more than 50% of cases being diagnosed in seven countries: India (27%), China (9%), Indonesia (8%), the Philippines (6%), Pakistan (6%), Nigeria (4%), and Bangladesh (4%). By 2021, the number of new cases each year was decreasing by around 2% annually. About 80% of people in many Asian and African countries test positive, while 5–10% of people in the United States test positive via the tuberculin test. Tuberculosis has been present in humans since ancient times.
== History ==
Tuberculosis has existed since antiquity. The oldest unambiguously detected M. tuberculosis gives evidence of the disease in the remains of bison in Wyoming dated to around 17,000 years ago. However, whether tuberculosis originated in bovines, then transferred to humans, or whether both bovine and human tuberculosis diverged from a common ancestor, remains unclear. A comparison of the genes of M. tuberculosis complex (MTBC) in humans to MTBC in animals suggests humans did not acquire MTBC from animals during animal domestication, as researchers previously believed. Both strains of the tuberculosis bacteria share a common ancestor, which could have infected humans even before the Neolithic Revolution. Skeletal remains show some prehistoric humans (4000 BC) had TB, and researchers have found tubercular decay in the spines of Egyptian mummies dating from 3000 to 2400 BC. Genetic studies suggest the presence of TB in the Americas from about AD 100.
Before the Industrial Revolution, folklore often associated tuberculosis with vampires. When one member of a family died from the disease, the other infected members would lose their health slowly. People believed this was caused by the original person with TB draining the life from the other family members.
=== Identification ===
Although Richard Morton established the pulmonary form associated with tubercles as a pathology in 1689, due to the variety of its symptoms, TB was not identified as a single disease until the 1820s. Benjamin Marten conjectured in 1720 that consumptions were caused by microbes which were spread by people living close to each other. In 1819, René Laennec claimed that tubercles were the cause of pulmonary tuberculosis. J. L. Schönlein first published the name "tuberculosis" (German: Tuberkulose) in 1832. Between 1838 and 1845, John Croghan, the owner of Mammoth Cave in Kentucky from 1839 onwards, brought a number of people with tuberculosis into the cave in the hope of curing the disease with the constant temperature and purity of the cave air; each died within a year. Hermann Brehmer opened the first TB sanatorium in 1859 in Görbersdorf (now Sokołowsko) in Silesia. In 1865, Jean Antoine Villemin demonstrated that tuberculosis could be transmitted, via inoculation, from humans to animals and among animals. (Villemin's findings were confirmed in 1867 and 1868 by John Burdon-Sanderson.)
Robert Koch identified and described the bacillus causing tuberculosis, M. tuberculosis, on 24 March 1882. In 1905, he was awarded the Nobel Prize in Physiology or Medicine for this discovery.
=== Development of treatments ===
In Europe, rates of tuberculosis began to rise in the early 1600s to a peak level in the 1800s, when it caused nearly 25% of all deaths. In the 18th and 19th century, tuberculosis had become epidemic in Europe, showing a seasonal pattern. Tuberculosis caused widespread public concern in the 19th and early 20th centuries as the disease became common among the urban poor. In 1815, one in four deaths in England was due to "consumption". By 1918, TB still caused one in six deaths in France. After TB was determined to be contagious, in the 1880s, it was put on a notifiable-disease list in Britain; campaigns started to stop people from spitting in public places, and the infected poor were "encouraged" to enter sanatoria that resembled prisons (the sanatoria for the middle and upper classes offered excellent care and constant medical attention). What later became known as the Alexandra Hospital for Children with Hip Disease (tuberculous arthritis) was opened in London in 1867. Whatever the benefits of the "fresh air" and labor in the sanatoria, even under the best conditions, 50% of those who entered died within five years (c. 1916).
Robert Koch did not believe the cattle and human tuberculosis diseases were similar, which delayed the recognition of infected milk as a source of infection. During the first half of the 1900s, the risk of transmission from this source was dramatically reduced after the application of the pasteurization process. Koch announced a glycerine extract of the tubercle bacilli as a "remedy" for tuberculosis in 1890, calling it "tuberculin". Although it was not effective, it was later successfully adapted as a screening test for the presence of pre-symptomatic tuberculosis. World Tuberculosis Day is marked on 24 March each year, the anniversary of Koch's original scientific announcement. When the Medical Research Council formed in Britain in 1913, it initially focused on tuberculosis research.
Albert Calmette and Camille Guérin achieved the first genuine success in immunization against tuberculosis in 1906, using attenuated bovine-strain tuberculosis. It was called bacille Calmette–Guérin (BCG). The BCG vaccine was first used on humans in 1921 in France, but achieved widespread acceptance in the US, Great Britain, and Germany only after World War II.
By the 1950s mortality in Europe had decreased about 90%. Improvements in sanitation, vaccination, and other public-health measures began significantly reducing rates of tuberculosis even before the arrival of streptomycin and other antibiotics, although the disease remained a significant threat. In 1946, the development of the antibiotic streptomycin made effective treatment and cure of TB a reality. Prior to the introduction of this medication, the only treatment was surgical intervention, including the "pneumothorax technique", which involved collapsing an infected lung to "rest" it and to allow tuberculous lesions to heal.
=== Current reemergence ===
Because of the emergence of multidrug-resistant tuberculosis (MDR-TB), surgery has been re-introduced for certain cases of TB infections. It involves the removal of infected chest cavities ("bullae") in the lungs to reduce the number of bacteria and to increase exposure of the remaining bacteria to antibiotics in the bloodstream. Hopes of eliminating TB ended with the rise of drug-resistant strains in the 1980s. The subsequent resurgence of tuberculosis resulted in the declaration of a global health emergency by the World Health Organization (WHO) in 1993.
== Signs and symptoms ==
Tuberculosis may infect any part of the body, but most commonly occurs in the lungs (known as pulmonary tuberculosis). Extrapulmonary TB occurs when tuberculosis develops outside of the lungs, although extrapulmonary TB may coexist with pulmonary TB.
General signs and symptoms include fever, chills, night sweats, loss of appetite, weight loss, and fatigue. Significant nail clubbing may also occur.
=== Pulmonary ===
If a tuberculosis infection does become active, it most commonly involves the lungs (in about 90% of cases). Symptoms may include chest pain and a prolonged cough producing sputum. About 25% of people may not have any symptoms (i.e., they remain asymptomatic). Occasionally, people may cough up blood in small amounts, and in very rare cases, the infection may erode into the pulmonary artery or a Rasmussen aneurysm, resulting in massive bleeding. Tuberculosis may become a chronic illness and cause extensive scarring in the upper lobes of the lungs. The upper lung lobes are more frequently affected by tuberculosis than the lower ones. The reason for this difference is not clear. It may be due to either better air flow, or poor lymph drainage within the upper lungs.
=== Extrapulmonary ===
In 15–20% of active cases, the infection spreads outside the lungs, causing other kinds of TB. These are collectively denoted as extrapulmonary tuberculosis. Extrapulmonary TB occurs more commonly in people with a weakened immune system and young children. In those with HIV, this occurs in more than 50% of cases. Notable extrapulmonary infection sites include the pleura (in tuberculous pleurisy), the central nervous system (in tuberculous meningitis), the lymphatic system (in scrofula of the neck), the genitourinary system (in urogenital tuberculosis), and the bones and joints (in Pott disease of the spine), among others. A potentially more serious, widespread form of TB is called "disseminated tuberculosis"; it is also known as miliary tuberculosis. Miliary TB currently makes up about 10% of extrapulmonary cases.
== Causes ==
=== Mycobacteria ===
The main cause of TB is Mycobacterium tuberculosis (MTB), a small, aerobic, nonmotile bacillus. The high lipid content of this pathogen accounts for many of its unique clinical characteristics. It divides every 16 to 20 hours, which is an extremely slow rate compared with other bacteria, which usually divide in less than an hour. Mycobacteria have an outer membrane lipid bilayer. If a Gram stain is performed, MTB either stains very weakly "Gram-positive" or does not retain dye as a result of the high lipid and mycolic acid content of its cell wall. MTB can withstand weak disinfectants and survive in a dry state for weeks. In nature, the bacterium can grow only within the cells of a host organism, but M. tuberculosis can be cultured in the laboratory.
Using histological stains on expectorated samples from phlegm (also called sputum), scientists can identify MTB under a microscope. Since MTB retains certain stains even after being treated with acidic solution, it is classified as an acid-fast bacillus. The most common acid-fast staining techniques are the Ziehl–Neelsen stain and the Kinyoun stain, which dye acid-fast bacilli a bright red that stands out against a blue background. Auramine-rhodamine staining and fluorescence microscopy are also used.
The M. tuberculosis complex (MTBC) includes four other TB-causing mycobacteria: M. bovis, M. africanum, M. canettii, and M. microti. M. africanum is not widespread, but it is a significant cause of tuberculosis in parts of Africa. M. bovis was once a common cause of tuberculosis, but the introduction of pasteurized milk has almost eliminated this as a public health problem in developed countries. M. canettii is rare and seems to be limited to the Horn of Africa, although a few cases have been seen in African emigrants. M. microti is also rare and is seen almost only in immunodeficient people, although its prevalence may be significantly underestimated.
Other known pathogenic mycobacteria include M. leprae, M. avium, and M. kansasii. The latter two species are classified as "nontuberculous mycobacteria" (NTM) or atypical mycobacteria. NTM cause neither TB nor leprosy, but they do cause lung diseases that resemble TB.
=== Transmission ===
When people with active pulmonary TB cough, sneeze, speak, sing, or spit, they expel infectious aerosol droplets 0.5 to 5.0 μm in diameter. A single sneeze can release up to 40,000 droplets. Each one of these droplets may transmit the disease, since the infectious dose of tuberculosis is very small (the inhalation of fewer than 10 bacteria may cause an infection).
==== Risk of transmission ====
People with prolonged, frequent, or close contact with people with TB are at particularly high risk of becoming infected, with an estimated 22% infection rate. A person with active but untreated tuberculosis may infect 10–15 (or more) other people per year. Transmission should occur from only people with active TB – those with latent infection are not thought to be contagious. The probability of transmission from one person to another depends upon several factors, including the number of infectious droplets expelled by the carrier, the effectiveness of ventilation, the duration of exposure, the virulence of the M. tuberculosis strain, the level of immunity in the uninfected person, and others. The cascade of person-to-person spread can be circumvented by segregating those with active ("overt") TB and putting them on anti-TB drug regimens. After about two weeks of effective treatment, subjects with nonresistant active infections generally do not remain contagious to others. If someone does become infected, it typically takes three to four weeks before the newly infected person becomes infectious enough to transmit the disease to others.
=== Risk factors ===
A number of factors make individuals more susceptible to TB infection and/or disease.
==== Active disease risk ====
The most important risk factor globally for developing active TB is concurrent HIV infection; 13% of those with TB are also infected with HIV. This is a particular problem in sub-Saharan Africa, where HIV infection rates are high. Of those without HIV infection who are infected with tuberculosis, about 5–10% develop active disease during their lifetimes; in contrast, 30% of those co-infected with HIV develop the active disease.
Use of certain medications, such as corticosteroids and infliximab (an anti-αTNF monoclonal antibody), is another important risk factor, especially in the developed world.
Other risk factors include: alcoholism, diabetes mellitus (3-fold increased risk), silicosis (30-fold increased risk), tobacco smoking (2-fold increased risk), indoor air pollution, malnutrition, young age, recently acquired TB infection, recreational drug use, severe kidney disease, low body weight, organ transplant, head and neck cancer, and genetic susceptibility (the overall importance of genetic risk factors remains undefined).
==== Infection susceptibility ====
Tobacco smoking increases the risk of infections (in addition to increasing the risk of active disease and death). Additional factors increasing infection susceptibility include young age.
== Pathogenesis ==
About 90% of those infected with M. tuberculosis have asymptomatic, latent TB infections (sometimes called LTBI), with only a 10% lifetime chance that the latent infection will progress to overt, active tuberculous disease. In those with HIV, the risk of developing active TB increases to nearly 10% a year. If effective treatment is not given, the death rate for active TB cases is up to 66%.
TB infection begins when the mycobacteria reach the alveolar air sacs of the lungs, where they invade and replicate within endosomes of alveolar macrophages. Macrophages identify the bacterium as foreign and attempt to eliminate it by phagocytosis. During this process, the bacterium is enveloped by the macrophage and stored temporarily in a membrane-bound vesicle called a phagosome. The phagosome then combines with a lysosome to create a phagolysosome. In the phagolysosome, the cell attempts to use reactive oxygen species and acid to kill the bacterium. However, M. tuberculosis has a thick, waxy mycolic acid capsule that protects it from these toxic substances. M. tuberculosis is able to reproduce inside the macrophage and will eventually kill the immune cell.
The primary site of infection in the lungs, known as the Ghon focus, is generally located in either the upper part of the lower lobe, or the lower part of the upper lobe. Tuberculosis of the lungs may also occur via infection from the blood stream. This is known as a Simon focus and is typically found in the top of the lung. This hematogenous transmission can also spread infection to more distant sites, such as peripheral lymph nodes, the kidneys, the brain, and the bones. All parts of the body can be affected by the disease, though for unknown reasons it rarely affects the heart, skeletal muscles, pancreas, or thyroid.
Tuberculosis is classified as one of the granulomatous inflammatory diseases. Macrophages, epithelioid cells, T lymphocytes, B lymphocytes, and fibroblasts aggregate to form granulomas, with lymphocytes surrounding the infected macrophages. When other macrophages attack the infected macrophage, they fuse together to form a giant multinucleated cell in the alveolar lumen. The granuloma may prevent dissemination of the mycobacteria and provide a local environment for interaction of cells of the immune system. However, more recent evidence suggests that the bacteria use the granulomas to avoid destruction by the host's immune system. Macrophages and dendritic cells in the granulomas are unable to present antigen to lymphocytes; thus the immune response is suppressed. Bacteria inside the granuloma can become dormant, resulting in latent infection. Another feature of the granulomas is the development of abnormal cell death (necrosis) in the center of tubercles. To the naked eye, this has the texture of soft, white cheese and is termed caseous necrosis.
If TB bacteria gain entry to the blood stream from an area of damaged tissue, they can spread throughout the body and set up many foci of infection, all appearing as tiny, white tubercles in the tissues. This severe form of TB disease, most common in young children and those with HIV, is called miliary tuberculosis. People with this disseminated TB have a high fatality rate even with treatment (about 30%).
In many people, the infection waxes and wanes. Tissue destruction and necrosis are often balanced by healing and fibrosis. Affected tissue is replaced by scarring and cavities filled with caseous necrotic material. During active disease, some of these cavities are joined to the air passages (bronchi) and this material can be coughed up. It contains living bacteria and thus can spread the infection. Treatment with appropriate antibiotics kills bacteria and allows healing to take place. Upon cure, affected areas are eventually replaced by scar tissue.
== Diagnosis ==
=== Active tuberculosis ===
Diagnosing active tuberculosis based only on signs and symptoms is difficult, as is diagnosing the disease in those who have a weakened immune system. A diagnosis of TB should, however, be considered in those with signs of lung disease or constitutional symptoms lasting longer than two weeks. A chest X-ray and multiple sputum cultures for acid-fast bacilli are typically part of the initial evaluation. Interferon-γ release assays (IGRA) and tuberculin skin tests are of little use in most of the developing world. IGRA have similar limitations in those with HIV.
A definitive diagnosis of TB is made by identifying M. tuberculosis in a clinical sample (e.g., sputum, pus, or a tissue biopsy). However, the difficult culture process for this slow-growing organism can take two to six weeks for blood or sputum culture. Thus, treatment is often begun before cultures are confirmed.
Nucleic acid amplification tests and adenosine deaminase testing may allow rapid diagnosis of TB. Blood tests to detect antibodies are not specific or sensitive, so they are not recommended.
=== Latent tuberculosis ===
The Mantoux tuberculin skin test is often used to screen people at high risk for TB. Those who have been previously immunized with the Bacille Calmette-Guerin vaccine may have a false-positive test result. The test may be falsely negative in those with sarcoidosis, Hodgkin's lymphoma, malnutrition, and most notably, active tuberculosis. Interferon gamma release assays, on a blood sample, are recommended in those who are positive to the Mantoux test. These are not affected by immunization or most environmental mycobacteria, so they generate fewer false-positive results. However, they are affected by M. szulgai, M. marinum, and M. kansasii. IGRAs may increase sensitivity when used in addition to the skin test, but may be less sensitive than the skin test when used alone.
The US Preventive Services Task Force (USPSTF) has recommended screening people who are at high risk for latent tuberculosis with either tuberculin skin tests or interferon-gamma release assays. While some have recommend testing health care workers, evidence of benefit for this is poor as of 2019. The Centers for Disease Control and Prevention (CDC) stopped recommending yearly testing of health care workers without known exposure in 2019.
== Prevention ==
Tuberculosis prevention and control efforts rely primarily on the vaccination of infants and the detection and appropriate treatment of active cases. The World Health Organization (WHO) has achieved some success with improved treatment regimens, and a small decrease in case numbers. Some countries have legislation to involuntarily detain or examine those suspected to have tuberculosis, or involuntarily treat them if infected.
=== Vaccines ===
The only available vaccine as of 2021 is bacillus Calmette-Guérin (BCG). In children it decreases the risk of getting the infection by 20% and the risk of infection turning into active disease by nearly 60%.
It is the most widely used vaccine worldwide, with more than 90% of all children being vaccinated. The immunity it induces decreases after about ten years. As tuberculosis is uncommon in most of Canada, Western Europe, and the United States, BCG is administered to only those people at high risk. Part of the reasoning against the use of the vaccine is that it makes the tuberculin skin test falsely positive, reducing the test's usefulness as a screening tool. Several vaccines are being developed.
Intradermal MVA85A vaccine in addition to BCG injection is not effective in preventing tuberculosis.
=== Public health ===
Public health campaigns which have focused on overcrowding, public spitting and regular sanitation (including hand washing) during the 1800s helped to either interrupt or slow spread which when combined with contact tracing, isolation and treatment helped to dramatically curb the transmission of both tuberculosis and other airborne diseases which led to the elimination of tuberculosis as a major public health issue in most developed economies. Other risk factors which worsened TB spread such as malnutrition were also ameliorated, but since the emergence of HIV a new population of immunocompromised individuals was available for TB to infect.
==== Source Control in the US ====
During the HIV/AIDS epidemic in the US, up to 35% of those affected by TB were also infected by HIV. Handling of TB-infected patients in US hospitals was known to create airborne TB that could infect others, especially in unventilated spaces.
Multiple US agencies rolled out new public health rules as a result of the TB spread: the CDC brought in new guidelines mandating HEPA filters and HEPA respirators, NIOSH pushed through new 42 CFR 84 respirator regulations in 1995 (like the N95), and OSHA created a proposed rule for TB in 1997, a result of pressure from groups like the Labor Coalition to Fight TB in the Workplace.
However, in 2003, OSHA dropped their proposed TB rules, citing a decline of TB in the US, and public disapproval.
==== Worldwide Campaigns ====
The World Health Organization (WHO) declared TB a "global health emergency" in 1993, and in 2006, the Stop TB Partnership developed a Global Plan to Stop Tuberculosis that aimed to save 14 million lives between its launch and 2015. A number of targets they set were not achieved by 2015, mostly due to the increase in HIV-associated tuberculosis and the emergence of multiple drug-resistant tuberculosis. A tuberculosis classification system developed by the American Thoracic Society is used primarily in public health programs. In 2015, it launched the End TB Strategy to reduce deaths by 95% and incidence by 90% before 2035. The goal of tuberculosis elimination is being hampered by the lack of rapid testing, short and effective treatment courses, and completely effective vaccines.
The benefits and risks of giving anti-tubercular drugs to those exposed to MDR-TB is unclear. Making HAART therapy available to HIV-positive individuals significantly reduces the risk of progression to an active TB infection by up to 90% and can mitigate the spread through this population.
== Management ==
Treatment of TB uses antibiotics to kill the bacteria. Effective TB treatment is difficult, due to the unusual structure and chemical composition of the mycobacterial cell wall, which hinders the entry of drugs and makes many antibiotics ineffective.
Active TB is best treated with combinations of several antibiotics to reduce the risk of the bacteria developing antibiotic resistance. The routine use of rifabutin instead of rifampicin in HIV-positive people with tuberculosis is of unclear benefit as of 2007.
Acetylsalicylic acid (aspirin) at a dose of 100 mg per day has been shown to improve clinical signs and symptoms, reduce cavitary lesions, lower inflammatory markers, and increase the rate of sputum-negative conversion in patients with pulmonary tuberculosis.
=== Latent TB ===
Latent TB is treated with either isoniazid or rifampin alone, or a combination of isoniazid with either rifampicin or rifapentine.
The treatment takes three to nine months depending on the medications used. People with latent infections are treated to prevent them from progressing to active TB disease later in life.
Education or counselling may improve the latent tuberculosis treatment completion rates.
=== New onset ===
The recommended treatment of new-onset pulmonary tuberculosis, as of 2010, is six months of a combination of antibiotics containing rifampicin, isoniazid, pyrazinamide, and ethambutol for the first two months, and only rifampicin and isoniazid for the last four months. Where resistance to isoniazid is high, ethambutol may be added for the last four months as an alternative. Treatment with anti-TB drugs for at least 6 months results in higher success rates when compared with treatment less than 6 months, even though the difference is small. Shorter treatment regimen may be recommended for those with compliance issues. There is also no evidence to support shorter anti-tuberculosis treatment regimens when compared to a 6-month treatment regimen. However, results presented in 2020 from an international, randomized, controlled clinical trial indicate that a four-month daily treatment regimen containing high-dose, or "optimized", rifapentine with moxifloxacin (2PHZM/2PHM) is as safe and effective as the existing standard six-month daily regimen at curing drug-susceptible tuberculosis (TB) disease.
=== Recurrent disease ===
If tuberculosis recurs, testing to determine which antibiotics it is sensitive to is important before determining treatment. If multiple drug-resistant TB (MDR-TB) is detected, treatment with at least four effective antibiotics for 18 to 24 months is recommended.
=== Medication administration ===
Directly observed therapy, i.e., having a health care provider watch the person take their medications, is recommended by the World Health Organization (WHO) in an effort to reduce the number of people not appropriately taking antibiotics. The evidence to support this practice over people simply taking their medications independently is of poor quality. There is no strong evidence indicating that directly observed therapy improves the number of people who were cured or the number of people who complete their medicine. Moderate quality evidence suggests that there is also no difference if people are observed at home versus at a clinic, or by a family member versus a health care worker. Methods to remind people of the importance of treatment and appointments may result in a small but important improvement. There is also not enough evidence to support intermittent rifampicin-containing therapy given two to three times a week has equal effectiveness as daily dose regimen on improving cure rates and reducing relapsing rates. There is also not enough evidence on effectiveness of giving intermittent twice or thrice weekly short course regimen compared to daily dosing regimen in treating children with tuberculosis.
=== Medication resistance ===
Primary resistance occurs when a person becomes infected with a resistant strain of TB. A person with fully susceptible MTB may develop secondary (acquired) resistance during therapy because of inadequate treatment, not taking the prescribed regimen appropriately (lack of compliance), or using low-quality medication. Drug-resistant TB is a serious public health issue in many developing countries, as its treatment is longer and requires more expensive drugs. MDR-TB is defined as resistance to the two most effective first-line TB drugs: rifampicin and isoniazid. Extensively drug-resistant TB is also resistant to three or more of the six classes of second-line drugs. Totally drug-resistant TB is resistant to all currently used drugs. It was first observed in 2003 in Italy, but not widely reported until 2012, and has also been found in Iran and India. There is some efficacy for linezolid to treat those with XDR-TB but side effects and discontinuation of medications were common. Bedaquiline is tentatively supported for use in multiple drug-resistant TB.
XDR-TB is a term sometimes used to define extensively resistant TB, and constitutes one in ten cases of MDR-TB. Cases of XDR TB have been identified in more than 90% of countries.
For those with known rifampicin or MDR-TB, molecular tests such as the Genotype MTBDRsl Assay (performed on culture isolates or smear positive specimens) may be useful to detect second-line anti-tubercular drug resistance.
== Prognosis ==
Progression from TB infection to overt TB disease occurs when the bacilli overcome the immune system defenses and begin to multiply. In primary TB disease (some 1–5% of cases), this occurs soon after the initial infection. However, in the majority of cases, a latent infection occurs with no obvious symptoms. These dormant bacilli produce active tuberculosis in 5–10% of these latent cases, often many years after infection.
The risk of reactivation increases with immunosuppression, such as that caused by infection with HIV. In people coinfected with M. tuberculosis and HIV, the risk of reactivation increases to 10% per year. Studies using DNA fingerprinting of M. tuberculosis strains have shown reinfection contributes more substantially to recurrent TB than previously thought, with estimates that it might account for more than 50% of reactivated cases in areas where TB is common. The chance of death from a case of tuberculosis is about 4% as of 2008, down from 8% in 1995.
In people with smear-positive pulmonary TB (without HIV co-infection), after 5 years without treatment, 50-60% die while 20-25% achieve spontaneous resolution (cure). TB is almost always fatal in those with untreated HIV co-infection and death rates are increased even with antiretroviral treatment of HIV.
== Epidemiology ==
Roughly one-quarter of the world's population has been infected with M. tuberculosis, with new infections occurring in about 1% of the population each year. However, most infections with M. tuberculosis do not cause disease, and 90–95% of infections remain asymptomatic. In 2012, an estimated 8.6 million chronic cases were active. In 2010, 8.8 million new cases of tuberculosis were diagnosed, and 1.20–1.45 million deaths occurred (most of these occurring in developing countries). Of these, about 0.35 million occur in those also infected with HIV. In 2018, tuberculosis was the leading cause of death worldwide from a single infectious agent. The total number of tuberculosis cases has been decreasing since 2005, while new cases have decreased since 2002.
Tuberculosis incidence is seasonal, with peaks occurring every spring and summer. The reasons for this are unclear, but may be related to vitamin D deficiency during the winter. There are also studies linking tuberculosis to different weather conditions like low temperature, low humidity and low rainfall. It has been suggested that tuberculosis incidence rates may be connected to climate change.
=== At-risk groups ===
Tuberculosis is closely linked to both overcrowding and malnutrition, making it one of the principal diseases of poverty. Those at high risk thus include: people who inject illicit drugs, inhabitants and employees of locales where vulnerable people gather (e.g., prisons and homeless shelters), medically underprivileged and resource-poor communities, high-risk ethnic minorities, children in close contact with high-risk category patients, and health-care providers serving these patients.
The rate of tuberculosis varies with age. In Africa, it primarily affects adolescents and young adults. However, in countries where incidence rates have declined dramatically (such as the United States), tuberculosis is mainly a disease of the elderly and immunocompromised (risk factors are listed above). Worldwide, 22 "high-burden" states or countries together experience 80% of cases as well as 83% of deaths.
In Canada and Australia, tuberculosis is many times more common among the Indigenous peoples, especially in remote areas. Factors contributing to this include higher prevalence of predisposing health conditions and behaviours, and overcrowding and poverty. In some Canadian Indigenous groups, genetic susceptibility may play a role.
Socioeconomic status (SES) strongly affects TB risk. People of low SES are both more likely to contract TB and to be more severely affected by the disease. Those with low SES are more likely to be affected by risk factors for developing TB (e.g., malnutrition, indoor air pollution, HIV co-infection, etc.), and are additionally more likely to be exposed to crowded and poorly ventilated spaces. Inadequate healthcare also means that people with active disease who facilitate spread are not diagnosed and treated promptly; sick people thus remain in the infectious state and (continue to) spread the infection.
=== Geographical epidemiology ===
The distribution of tuberculosis is not uniform across the globe; about 80% of the population in many African, Caribbean, South Asian, and eastern European countries test positive in tuberculin tests, while only 5–10% of the U.S. population test positive. Hopes of totally controlling the disease have been dramatically dampened because of many factors, including the difficulty of developing an effective vaccine, the expensive and time-consuming diagnostic process, the necessity of many months of treatment, the increase in HIV-associated tuberculosis, and the emergence of drug-resistant cases in the 1980s.
In developed countries, tuberculosis is less common and is found mainly in urban areas. In Europe, deaths from TB fell from 500 out of 100,000 in 1850 to 50 out of 100,000 by 1950. Improvements in public health were reducing tuberculosis even before the arrival of antibiotics, although the disease remained a significant threat to public health, such that when the Medical Research Council was formed in Britain in 1913 its initial focus was tuberculosis research.
In 2010, rates per 100,000 people in different areas of the world were: globally 178, Africa 332, the Americas 36, Eastern Mediterranean 173, Europe 63, Southeast Asia 278, and Western Pacific 139.
==== Russia ====
Russia has achieved particularly dramatic progress with a decline in its TB mortality rate—from 61.9 per 100,000 in 1965 to 2.7 per 100,000 in 1993; however, mortality rate increased to 24 per 100,000 in 2005 and then recoiled to 11 per 100,000 by 2015.
==== China ====
China has achieved particularly dramatic progress, with about an 80% reduction in its TB mortality rate between 1990 and 2010. The number of new cases has declined by 17% between 2004 and 2014.
==== Africa ====
In 2007, the country with the highest estimated incidence rate of TB was Eswatini, with 1,200 cases per 100,000 people. In 2017, the country with the highest estimated incidence rate as a % of the population was Lesotho, with 665 cases per 100,000 people.
In South Africa, 54,200 people died in 2022 from TB. The incidence rate was 468 per 100,000 people; in 2015, this was 988 per 100,000. The total incidence was 280,000 in 2022; in 2015, this was 552,000.
==== India ====
As of 2017, India had the largest total incidence, with an estimated 2,740,000 cases. According to the World Health Organization (WHO), in 2000–2015, India's estimated mortality rate dropped from 55 to 36 per 100,000 population per year with estimated 480 thousand people died of TB in 2015. In India a major proportion of tuberculosis patients are being treated by private partners and private hospitals. Evidence indicates that the tuberculosis national survey does not represent the number of cases that are diagnosed and recorded by private clinics and hospitals in India.
==== North America ====
In the United States, Native Americans have a fivefold greater mortality from TB, and racial and ethnic minorities accounted for 84% of all reported TB cases. The overall tuberculosis case rate in the United States was 3 per 100,000 persons in 2017.
In Canada, tuberculosis was endemic in some rural areas as of 1998.
==== Western Europe ====
In 2017, in the United Kingdom, the national average was 9 per 100,000 and the highest incidence rates in Western Europe were 20 per 100,000 in Portugal.
== Society and culture ==
=== Names ===
Tuberculosis has been known by many names from the technical to the familiar. Phthisis (φθίσις) is the Greek word for consumption, an old term for pulmonary tuberculosis; around 460 BCE, Hippocrates described phthisis as a disease of dry seasons. The abbreviation TB is short for tubercle bacillus. Consumption was the most common nineteenth century English word for the disease, and was also in use well into the twentieth century. The Latin root con meaning 'completely' is linked to sumere meaning 'to take up from under'. In The Life and Death of Mr Badman by John Bunyan, the author calls consumption "the captain of all these men of death." "Great white plague" has also been used.
=== Art and literature ===
Tuberculosis was for centuries associated with poetic and artistic qualities among those infected, and was also known as "the romantic disease". Major artistic figures such as the poets John Keats, Percy Bysshe Shelley, and Edgar Allan Poe, the composer Frédéric Chopin, the playwright Anton Chekhov, the novelists Franz Kafka, Katherine Mansfield, Charlotte Brontë, Fyodor Dostoevsky, Thomas Mann, W. Somerset Maugham, George Orwell, and Robert Louis Stevenson, and the artists Alice Neel, Jean-Antoine Watteau, Elizabeth Siddal, Marie Bashkirtseff, Edvard Munch, Aubrey Beardsley and Amedeo Modigliani either had the disease or were surrounded by people who did. A widespread belief was that tuberculosis assisted artistic talent. Physical mechanisms proposed for this effect included the slight fever and toxaemia that it caused, allegedly helping them to see life more clearly and to act decisively.
Tuberculosis formed an often-reused theme in literature, as in Thomas Mann's The Magic Mountain, set in a sanatorium; in music, as in Van Morrison's song "T.B. Sheets"; in opera, as in Puccini's La bohème and Verdi's La Traviata; in art, as in Munch's painting of his ill sister; and in film, such as the 1945 The Bells of St. Mary's starring Ingrid Bergman as a nun with tuberculosis.
=== Public health efforts ===
In 2014, the WHO adopted the "End TB" strategy which aims to reduce TB incidence by 80% and TB deaths by 90% by 2030. The strategy contains a milestone to reduce TB incidence by 20% and TB deaths by 35% by 2020. However, by 2020 only a 9% reduction in incidence per population was achieved globally, with the European region achieving 19% and the African region achieving 16% reductions. Similarly, the number of deaths only fell by 14%, missing the 2020 milestone of a 35% reduction, with some regions making better progress (31% reduction in Europe and 19% in Africa). Correspondingly, also treatment, prevention and funding milestones were missed in 2020, for example only 6.3 million people were started on TB prevention short of the target of 30 million.
The World Health Organization (WHO), the Bill and Melinda Gates Foundation, and the U.S. government are subsidizing a fast-acting diagnostic tuberculosis test for use in low- and middle-income countries as of 2012. In addition to being fast-acting, the test can determine if there is resistance to the antibiotic rifampicin which may indicate multi-drug resistant tuberculosis and is accurate in those who are also infected with HIV. Many resource-poor places as of 2011 have access to only sputum microscopy.
India had the highest total number of TB cases worldwide in 2010, in part due to poor disease management within the private and public health care sector. Programs such as the Revised National Tuberculosis Control Program are working to reduce TB levels among people receiving public health care.
A 2014 EIU-healthcare report finds there is a need to address apathy and urges for increased funding. The report cites among others Lucica Ditui "[TB] is like an orphan. It has been neglected even in countries with a high burden and often forgotten by donors and those investing in health interventions."
Slow progress has led to frustration, expressed by the executive director of the Global Fund to Fight AIDS, Tuberculosis and Malaria – Mark Dybul: "we have the tools to end TB as a pandemic and public health threat on the planet, but we are not doing it." Several international organizations are pushing for more transparency in treatment, and more countries are implementing mandatory reporting of cases to the government as of 2014, although adherence is often variable. Commercial treatment providers may at times overprescribe second-line drugs as well as supplementary treatment, promoting demands for further regulations. The government of Brazil provides universal TB care, which reduces this problem. Conversely, falling rates of TB infection may not relate to the number of programs directed at reducing infection rates but may be tied to an increased level of education, income, and health of the population. Costs of the disease, as calculated by the World Bank in 2009 may exceed US$150 billion per year in "high burden" countries. Lack of progress eradicating the disease may also be due to lack of patient follow-up – as among the 250 million rural migrants in China.
There is insufficient data to show that active contact tracing helps to improve case detection rates for tuberculosis. Interventions such as house-to-house visits, educational leaflets, mass media strategies, educational sessions may increase tuberculosis detection rates in short-term. There is no study that compares new methods of contact tracing such as social network analysis with existing contact tracing methods.
=== Stigma ===
Slow progress in preventing the disease may in part be due to stigma associated with TB. Stigma may be due to the fear of transmission from affected individuals. This stigma may additionally arise due to links between TB and poverty, and in Africa, AIDS. Such stigmatization may be both real and perceived; for example, in Ghana, individuals with TB are banned from attending public gatherings.
Stigma towards TB may result in delays in seeking treatment, lower treatment compliance, and family members keeping cause of death secret – allowing the disease to spread further. In contrast, in Russia stigma was associated with increased treatment compliance. TB stigma also affects socially marginalized individuals to a greater degree and varies between regions.
One way to decrease stigma may be through the promotion of "TB clubs", where those infected may share experiences and offer support, or through counseling. Some studies have shown TB education programs to be effective in decreasing stigma, and may thus be effective in increasing treatment adherence. Despite this, studies on the relationship between reduced stigma and mortality are lacking as of 2010, and similar efforts to decrease stigma surrounding AIDS have been minimally effective. Some have claimed the stigma to be worse than the disease, and healthcare providers may unintentionally reinforce stigma, as those with TB are often perceived as difficult or otherwise undesirable. A greater understanding of the social and cultural dimensions of tuberculosis may also help with stigma reduction.
== Research ==
The BCG vaccine has limitations, and research to develop new TB vaccines is ongoing. A number of potential candidates are currently in phase I and II clinical trials. Two main approaches are used to attempt to improve the efficacy of available vaccines. One approach involves adding a subunit vaccine to BCG, while the other strategy is attempting to create new and better live vaccines. MVA85A, an example of a subunit vaccine, is in trials in South Africa as of 2006, is based on a genetically modified vaccinia virus. Vaccines are hoped to play a significant role in treatment of both latent and active disease.
To encourage further discovery, researchers and policymakers are promoting new economic models of vaccine development as of 2006, including prizes, tax incentives, and advance market commitments. A number of groups, including the Stop TB Partnership, the South African Tuberculosis Vaccine Initiative, and the Aeras Global TB Vaccine Foundation, are involved with research. Among these, the Aeras Global TB Vaccine Foundation received a gift of more than $280 million (US) from the Bill and Melinda Gates Foundation to develop and license an improved vaccine against tuberculosis for use in high burden countries.
In 2012 a new medication regimen was approved in the US for multidrug-resistant tuberculosis, using bedaquiline as well as existing drugs. There were initial concerns about the safety of this drug, but later research on larger groups found that this regimen improved health outcomes. By 2017 the drug was used in at least 89 countries. Another new drug is delamanid, which was first approved by the European Medicines Agency in 2013 to be used in multidrug-resistant tuberculosis patients, and by 2017 was used in at least 54 countries.
Steroids add-on therapy has not shown any benefits for active pulmonary tuberculosis infection.
== Other animals ==
Mycobacteria infect many different animals, including birds, fish, rodents, and reptiles. The subspecies Mycobacterium tuberculosis, though, is rarely present in wild animals. An effort to eradicate bovine tuberculosis caused by Mycobacterium bovis from the cattle and deer herds of New Zealand has been relatively successful. Efforts in Great Britain have been less successful.
As of 2015, tuberculosis appears to be widespread among captive elephants in the US. It is believed that the animals originally acquired the disease from humans, a process called reverse zoonosis. Because the disease can spread through the air to infect both humans and other animals, it is a public health concern affecting circuses and zoos.
== See also ==
List of deaths due to tuberculosis
== Notes ==
== References ==
== External links ==
Tuberculosis at Curlie
"Tuberculosis (TB)". Centers for Disease Control and Prevention (CDC). 24 October 2018.
"Tuberculosis (TB)". London: Health Protection Agency. Archived from the original on 5 July 2007.
WHO global 2016 TB report (infographic)
WHO tuberculosis country profiles
"Tuberculosis Among African Americans", 1990-11-01, In Black America; KUT Radio, American Archive of Public Broadcasting (WGBH and the Library of Congress)
Working Group on New TB drugs, tracking clinical trials and drug candidates | Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is an infectious disease usually caused by Mycobacterium tuberculosis (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in which case it is known as latent tuberculosis. Around 10% of latent infections progress to active disease which, if left untreated, kill about half of those affected. Typical symptoms of active TB are chronic cough with blood-containing mucus, fever, night sweats, and weight loss. Infection of other organs can cause a wide range of symptoms.
Tuberculosis is spread from one person to the next through the air when people who have active TB in their lungs cough, spit, speak, or sneeze. People with latent TB do not spread the disease. Active infection occurs more often in people with HIV/AIDS and in those who smoke. Diagnosis of active TB is based on chest X-rays, as well as microscopic examination and culture of body fluids. Diagnosis of latent TB relies on the tuberculin skin test (TST) or blood tests.
Prevention of TB involves screening those at high risk, early detection and treatment of cases, and vaccination with the bacillus Calmette-Guérin (BCG) vaccine. Those at high risk include household, workplace, and social contacts of people with active TB. Treatment requires the use of multiple antibiotics over a long period of time. Antibiotic resistance is a growing problem, with increasing rates of multiple drug-resistant tuberculosis (MDR-TB).
In 2018, one quarter of the world's population was thought to have a latent infection of TB. New infections occur in about 1% of the population each year. In 2022, an estimated 10.6 million people developed active TB, resulting in 1.3 million deaths, making it the second leading cause of death from an infectious disease after COVID-19. As of 2018, most TB cases occurred in the regions of South-East Asia (44%), Africa (24%), and the Western Pacific (18%), with more than 50% of cases being diagnosed in seven countries: India (27%), China (9%), Indonesia (8%), the Philippines (6%), Pakistan (6%), Nigeria (4%), and Bangladesh (4%). By 2021, the number of new cases each year was decreasing by around 2% annually. About 80% of people in many Asian and African countries test positive, while 5–10% of people in the United States test positive via the tuberculin test. Tuberculosis has been present in humans since ancient times.
| 21 |
785 | love | Liebe (wiktionary) | From Middle High German liebe (“joy, affection, kindliness”), from Old High German liob, lioba (“fortune, health, pleasantness, joy”), from Proto-West Germanic *leubu (“love”). Related with Old High German luba, English love (from Proto-Germanic *lubō).
IPA(key): /ˈliːbə/
Rhymes: -iːbə
Hyphenation: Lie‧be
Liebe f (genitive Liebe, plural Lieben)
(uncountable) love (tender feeling of affection)
1787, Johann Wolfgang von Goethe, Egmont
(countable) a feeling of love for someone or something particular
(countable) a love relationship
(uncountable, euphemistic) sex; sexual relations; sexual intercourse
(love): Minne; Zuneigung
(sexual relations): Sex, Geschlechtsakt, Geschlechtsverkehr
(antonym(s) of “love”): Hass, Abneigung, Ekel, Gleichgültigkeit
lieb
lieben
Liebe on the German Wikipedia.Wikipedia de
“Liebe” in Duden online
“Liebe” in Digitales Wörterbuch der deutschen Sprache
“Liebe” in Deutsches Wörterbuch von Jacob und Wilhelm Grimm, 16 vols., Leipzig 1854–1961.
“Liebe” in Uni Leipzig: Wortschatz-Lexikon | From Middle High German liebe (“joy, affection, kindliness”), from Old High German liob, lioba (“fortune, health, pleasantness, joy”), from Proto-West Germanic *leubu (“love”). Related with Old High German luba, English love (from Proto-Germanic *lubō).
IPA(key): /ˈliːbə/
Rhymes: -iːbə
Hyphenation: Lie‧be
Liebe f (genitive Liebe, plural Lieben)
(uncountable) love (tender feeling of affection)
1787, Johann Wolfgang von Goethe, Egmont
(countable) a feeling of love for someone or something particular
(countable) a love relationship
(uncountable, euphemistic) sex; sexual relations; sexual intercourse
(love): Minne; Zuneigung
(sexual relations): Sex, Geschlechtsakt, Geschlechtsverkehr
(antonym(s) of “love”): Hass, Abneigung, Ekel, Gleichgültigkeit
lieb
lieben
Liebe on the German Wikipedia.Wikipedia de
“Liebe” in Duden online
“Liebe” in Digitales Wörterbuch der deutschen Sprache
“Liebe” in Deutsches Wörterbuch von Jacob und Wilhelm Grimm, 16 vols., Leipzig 1854–1961.
“Liebe” in Uni Leipzig: Wortschatz-Lexikon | 14 |
786 | love | liebe (wiktionary) | IPA(key): /ˈliːbə/
liebe
inflection of lieb:
strong/mixed nominative/accusative feminine singular
strong nominative/accusative plural
weak nominative all-gender singular
weak accusative feminine/neuter singular
liebe
inflection of lieben:
first-person singular present
first/third-person singular subjunctive I
singular imperative | IPA(key): /ˈliːbə/
liebe
inflection of lieb:
strong/mixed nominative/accusative feminine singular
strong nominative/accusative plural
weak nominative all-gender singular
weak accusative feminine/neuter singular
liebe
inflection of lieben:
first-person singular present
first/third-person singular subjunctive I
singular imperative | 4 |
787 | love | love (wiktionary) | loue (obsolete typography)
luv
enPR: lŭv
(Received Pronunciation, General American, Canada) IPA(key): /lʌv/
(General Australian) IPA(key): /lav/, [läv~lɐv]
(India) IPA(key): /lʌv/, [lɘʋ], [lɘv]
(Northern England, Ireland) IPA(key): /lʊv/
Rhymes: -ʌv
From Middle English love, luve, from Old English lufu, from Proto-West Germanic *lubu, from Proto-Germanic *lubō, from Proto-Indo-European *lewbʰ- (“love, care, desire”).
The close of a letter sense is presumably a truncation of With love or the like.
The verb is from Middle English loven, luvien, from Old English lufian (“to love”), from Proto-West Germanic *lubōn (“to love”), derived from the noun.
Eclipsed non-native English amour (“love”), borrowed from French amour (“love”).
Cognates include Russian любовь (ljubovʹ), Latin libido (“desire, lust”), Polish lubić and Sanskrit लोभ (lobha, “desire, greed”).
love (countable and uncountable, plural loves)
(uncountable) A deep caring for the existence of another.
(uncountable) Strong affection.
Antonyms: hate, hatred, angst, indifference
A profound and caring affection towards someone.
Affectionate, benevolent concern or care for other people or beings, and for their well-being.
1864, Utilitarianism Explained and Exemplified in Moral and Political Government:
The love of your neighbor as yourself, is expressly given as the definition and test of Charity,—not alms-giving—and this love is [...] the highest of all the Divine commands[.]
A feeling of intense attraction towards someone.
A deep or abiding liking for something; an enthusiasm for something.
(countable) A person who is the object of romantic feelings; a darling, a sweetheart, a beloved.
Synonyms: baby, darling, honey, lover, pet, sweetheart; see also Thesaurus:sweetheart
(colloquial, Commonwealth) A term of friendly address, regardless of feelings.
Synonyms: mate, darling, lovey, sweetie, sweetheart
A thing, activity, etc. which is the object of one's deep liking or enthusiasm.
(euphemistic) Sexual desire; attachment based on sexual attraction.
Synonyms: aphrodisia, carnality; see also Thesaurus:lust
(euphemistic) Sexual activity.
Synonyms: lovemaking, sex; see also Thesaurus:copulation
An instance or episode of being in love; a love affair.
Synonym: romance
Used as the closing, before the signature, of a letter, especially between good friends or family members, or by the young.
Alternative letter-case form of Love (“personification of love”).
c. 1810, Samuel Johnson (in The Works of Samuel Johnson):
At busy hearts in vain love's arrows fly; [...]
(obsolete) A thin silk material.
A climbing plant, Clematis vitalba.
love (third-person singular simple present loves, present participle loving, simple past and past participle loved)
(usually transitive, sometimes intransitive, stative) To have a strong affection for (someone or something).
(transitive) To need, thrive on.
(transitive) To be strongly inclined towards something; an emphatic form of like.
(usually transitive, sometimes intransitive) To seek the good or honor of (someone), care deeply about, to be dedicated to (someone or something).
(transitive, sometimes ironic) To derive delight from a fact or situation.
(Internet) Synonym of heart (verb).
Coordinate terms: like, unlike
(transitive, euphemistic) To have sex with (perhaps from make love).
(have a strong affection for): adore, cherish; see also Thesaurus:love
(have sexual intercourse with): enjoy, go to bed with, sleep with; see also Thesaurus:copulate with
hate, despise, fear
Sranan Tongo: lobi
Aukan: lobi
Saramaccan: lóbi
charity
Now widely believed (due to historical written record) to be from the idea that when one does a thing “for love” it is for no monetary gain, the word “love” thus implying "nothing".
The former assumption that it had originated from French l’œuf (literally “the egg”), due to its shape, has largely been discredited and is no longer widely accepted. However, the apparent similarity of the shape of an egg to a zero has inspired similar analogies, such as the use of duck (reputed to be short for duck's egg) for a zero score at cricket, and goose egg for "zero".
love (uncountable)
(racquet sports, billiards) Zero, no score.
So that’s fifteen-love to Kournikova.
Nothing; no recompense.
love (third-person singular simple present loves, present participle loving, simple past and past participle loved)
Alternative form of lofe (“to praise, sell”)
“love”, in OneLook Dictionary Search.
love in Keywords for Today: A 21st Century Vocabulary, edited by The Keywords Project, Colin MacCabe, Holly Yanacek, 2018.
“love”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.
levo, levo-, velo-, vole, voël
IPA(key): [ˈlovɛ]
Hyphenation: lo‧ve
Borrowed from Romani love.
love f pl (indeclinable)
(slang) money
Synonym: prachy
See the etymology of the corresponding lemma form.
love m
vocative singular of lov
love in Kartotéka Novočeského lexikálního archivu
IPA(key): /ˈlɔːvə/, [ˈlɔːʋə], [ˈlɔːʊ]
From Middle Low German lōve, from Proto-Germanic *galaubô, cognate with German Glaube.
love c
(obsolete) trust, faith
only in the phrase på tro og love (“solemnly”)
“love,1” in Den Danske Ordbog
From Old Norse lofa, from Proto-Germanic *(ga)lubōną, cognate with Swedish lova (“to promise; to praise”), German loben (“to praise”), geloben (“to vow”), Dutch loven (“to praise”).
love (past tense lovede, past participle lovet)
to promise
(solemn) to praise
“love,2” in Den Danske Ordbog
“love,3” in Den Danske Ordbog
See See the etymology of the corresponding lemma form.
love c
indefinite plural of lov
love
(dated or formal) singular present subjunctive of loven
velo, voel
love
inflection of lover:
first-person /third-person singular present indicative/subjunctive
second-person singular imperative
vélo, vole, volé
From Latin lupa, feminine of lupus. Compare Venetian lova, French louve.
love f (plural lovis)
she-wolf
lôf
Inherited from Middle High German loben, from Old High German lobōn, from Proto-West Germanic *lobōn, from Proto-Germanic *lubōną.
Cognate with German loben, Luxembourgish luewen.
IPA(key): /ˈloːvə/
Rhymes: -oːvə
Hyphenation: lo‧ve
love
(transitive) to praise [with accusative]
From Proto-Samic *lokē
love
ten
This numeral needs an inflection-table template.
love in Marja-Liisa Olthuis, Taarna Valtonen, Miina Seurujärvi and Trond Trosterud (2015–2022) Nettidigisäänih Anarâškiela-suomakielâ-anarâškielâ sänikirje[3], Tromsø: UiT
Koponen, Eino, Ruppel, Klaas, Aapala, Kirsti, editors (2002–2008), Álgu database: Etymological database of the Saami languages[4], Helsinki: Research Institute for the Languages of Finland
lōve
dative singular of lof
Inherited from Old English lufu, from Proto-West Germanic *lubu, from Proto-Germanic *lubō.
lof, lofe, louf, luf, lufe, luff, luffe, luve
leove, lofve, lufæ (Early Middle English)
IPA(key): /ˈluv(ə)/, /ˈloːv(ə)/
love (plural loves)
Love; strong and deep affection:
Sexual or romantic desire (in humans and other animals)
Theosis, sanctification, or love as a means to attain it.
One who one loves; a loved individual:
A lover; a sexual or romantic partner.
A personification or embodiment of love.
(Christianity) The Holy Spirit (or less often, God generally).
A peace treaty; the ending of hostilities.
(rare) Permission, consent.
English: love
Scots: luve, lufe
Yola: loove
“lǒve, n.(1).”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007.
Inherited from Old English lāfe, oblique singular of lāf, from Proto-West Germanic *laibu, from Proto-Germanic *laibō; compare leven (“to halt”), which some forms are influenced by.
lave, leve, loove
lafe, læve, loave (Early Middle English)
IPA(key): /ˈlɔːv(ə)/
(Northern) IPA(key): /laːf/, /ˈlaːv(ə)/
love (uncountable)
The remainder or rest; that which is left.
(rare) A widow; a woman whose husband has died.
Synonyms: relicte, widwe
English: lave
Scots: lave
“lōve, n.(2).”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007.
Borrowed from Old Norse lófi, from Proto-Germanic *lōfô; compare glove.
lof, loove, louf, luf, lufe, luff, luffe
IPA(key): /ˈloːv(ə)/, /loːf/
love (plural loves)
(chiefly Northern) The palm (inner part of the hand)
English: loof
Scots: luif, lufe, luff
“lọ̄ve, n.(3).”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007.
love
Alternative form of loven (“to love”)
love
Alternative form of loven (“to praise”)
From Old Norse lofa.
love (imperative lov, present tense lover, simple past and past participle lova or lovet, present participle lovende)
to praise
love (imperative lov, present tense lover, simple past lova or lovet or lovte or lovde, past participle lova or lovet or lovt or lovd, present participle lovende)
to promise
(as an adjective) det lovede land - the Promised Land
løfte
“love” in The Bokmål Dictionary.
love (present tense lovar or lover, past tense lova or lovde, past participle lova or lovt or lovd, present participle lovande, imperative lov)
Alternative form of lova
love m (definite singular loven, indefinite plural lovar, definite plural lovane)
Alternative form of lóve
vole
love
plural of lovo
money
→ French: lové
→ Hungarian: lóvé
→ Romanian: lovea
→ Russian: лавэ́ (lavɛ́)
→ Scots: lowie
→ Serbo-Croatian:
Cyrillic script: ло́ва
Latin script: lóva
→ Slovak: lóve
love (Cyrillic spelling лове)
vocative singular of lov
love (Cyrillic spelling лове)
third-person plural present of loviti
love c
(chiefly in compounds) wrist (connecting the hand to the forearm)
handlov
love in Svensk ordbok (SO)
love in Svenska Akademiens ordbok (SAOB) | loue (obsolete typography)
luv
enPR: lŭv
(Received Pronunciation, General American, Canada) IPA(key): /lʌv/
(General Australian) IPA(key): /lav/, [läv~lɐv]
(India) IPA(key): /lʌv/, [lɘʋ], [lɘv]
(Northern England, Ireland) IPA(key): /lʊv/
Rhymes: -ʌv
From Middle English love, luve, from Old English lufu, from Proto-West Germanic *lubu, from Proto-Germanic *lubō, from Proto-Indo-European *lewbʰ- (“love, care, desire”).
The close of a letter sense is presumably a truncation of With love or the like.
The verb is from Middle English loven, luvien, from Old English lufian (“to love”), from Proto-West Germanic *lubōn (“to love”), derived from the noun.
Eclipsed non-native English amour (“love”), borrowed from French amour (“love”).
Cognates include Russian любовь (ljubovʹ), Latin libido (“desire, lust”), Polish lubić and Sanskrit लोभ (lobha, “desire, greed”).
love (countable and uncountable, plural loves)
(uncountable) A deep caring for the existence of another.
(uncountable) Strong affection.
Antonyms: hate, hatred, angst, indifference
A profound and caring affection towards someone.
Affectionate, benevolent concern or care for other people or beings, and for their well-being.
1864, Utilitarianism Explained and Exemplified in Moral and Political Government:
The love of your neighbor as yourself, is expressly given as the definition and test of Charity,—not alms-giving—and this love is [...] the highest of all the Divine commands[.]
A feeling of intense attraction towards someone.
A deep or abiding liking for something; an enthusiasm for something.
(countable) A person who is the object of romantic feelings; a darling, a sweetheart, a beloved.
Synonyms: baby, darling, honey, lover, pet, sweetheart; see also Thesaurus:sweetheart
(colloquial, Commonwealth) A term of friendly address, regardless of feelings.
Synonyms: mate, darling, lovey, sweetie, sweetheart
A thing, activity, etc. which is the object of one's deep liking or enthusiasm.
(euphemistic) Sexual desire; attachment based on sexual attraction.
Synonyms: aphrodisia, carnality; see also Thesaurus:lust
(euphemistic) Sexual activity.
Synonyms: lovemaking, sex; see also Thesaurus:copulation
An instance or episode of being in love; a love affair.
Synonym: romance
Used as the closing, before the signature, of a letter, especially between good friends or family members, or by the young.
Alternative letter-case form of Love (“personification of love”).
c. 1810, Samuel Johnson (in The Works of Samuel Johnson):
At busy hearts in vain love's arrows fly; [...]
(obsolete) A thin silk material.
A climbing plant, Clematis vitalba.
love (third-person singular simple present loves, present participle loving, simple past and past participle loved)
(usually transitive, sometimes intransitive, stative) To have a strong affection for (someone or something).
(transitive) To need, thrive on.
(transitive) To be strongly inclined towards something; an emphatic form of like.
(usually transitive, sometimes intransitive) To seek the good or honor of (someone), care deeply about, to be dedicated to (someone or something).
(transitive, sometimes ironic) To derive delight from a fact or situation.
(Internet) Synonym of heart (verb).
Coordinate terms: like, unlike
(transitive, euphemistic) To have sex with (perhaps from make love).
(have a strong affection for): adore, cherish; see also Thesaurus:love
(have sexual intercourse with): enjoy, go to bed with, sleep with; see also Thesaurus:copulate with
hate, despise, fear
Sranan Tongo: lobi
Aukan: lobi
Saramaccan: lóbi
charity
Now widely believed (due to historical written record) to be from the idea that when one does a thing “for love” it is for no monetary gain, the word “love” thus implying "nothing".
The former assumption that it had originated from French l’œuf (literally “the egg”), due to its shape, has largely been discredited and is no longer widely accepted. However, the apparent similarity of the shape of an egg to a zero has inspired similar analogies, such as the use of duck (reputed to be short for duck's egg) for a zero score at cricket, and goose egg for "zero".
love (uncountable)
(racquet sports, billiards) Zero, no score.
So that’s fifteen-love to Kournikova.
Nothing; no recompense.
love (third-person singular simple present loves, present participle loving, simple past and past participle loved)
Alternative form of lofe (“to praise, sell”)
“love”, in OneLook Dictionary Search.
love in Keywords for Today: A 21st Century Vocabulary, edited by The Keywords Project, Colin MacCabe, Holly Yanacek, 2018.
“love”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.
levo, levo-, velo-, vole, voël
IPA(key): [ˈlovɛ]
Hyphenation: lo‧ve
Borrowed from Romani love.
love f pl (indeclinable)
(slang) money
Synonym: prachy
See the etymology of the corresponding lemma form.
love m
vocative singular of lov
love in Kartotéka Novočeského lexikálního archivu
IPA(key): /ˈlɔːvə/, [ˈlɔːʋə], [ˈlɔːʊ]
From Middle Low German lōve, from Proto-Germanic *galaubô, cognate with German Glaube.
love c
(obsolete) trust, faith
only in the phrase på tro og love (“solemnly”)
“love,1” in Den Danske Ordbog
From Old Norse lofa, from Proto-Germanic *(ga)lubōną, cognate with Swedish lova (“to promise; to praise”), German loben (“to praise”), geloben (“to vow”), Dutch loven (“to praise”).
love (past tense lovede, past participle lovet)
to promise
(solemn) to praise
“love,2” in Den Danske Ordbog
“love,3” in Den Danske Ordbog
See See the etymology of the corresponding lemma form.
love c
indefinite plural of lov
love
(dated or formal) singular present subjunctive of loven
velo, voel
love
inflection of lover:
first-person /third-person singular present indicative/subjunctive
second-person singular imperative
vélo, vole, volé
From Latin lupa, feminine of lupus. Compare Venetian lova, French louve.
love f (plural lovis)
she-wolf
lôf
Inherited from Middle High German loben, from Old High German lobōn, from Proto-West Germanic *lobōn, from Proto-Germanic *lubōną.
Cognate with German loben, Luxembourgish luewen.
IPA(key): /ˈloːvə/
Rhymes: -oːvə
Hyphenation: lo‧ve
love
(transitive) to praise [with accusative]
From Proto-Samic *lokē
love
ten
This numeral needs an inflection-table template.
love in Marja-Liisa Olthuis, Taarna Valtonen, Miina Seurujärvi and Trond Trosterud (2015–2022) Nettidigisäänih Anarâškiela-suomakielâ-anarâškielâ sänikirje[3], Tromsø: UiT
Koponen, Eino, Ruppel, Klaas, Aapala, Kirsti, editors (2002–2008), Álgu database: Etymological database of the Saami languages[4], Helsinki: Research Institute for the Languages of Finland
lōve
dative singular of lof
Inherited from Old English lufu, from Proto-West Germanic *lubu, from Proto-Germanic *lubō.
lof, lofe, louf, luf, lufe, luff, luffe, luve
leove, lofve, lufæ (Early Middle English)
IPA(key): /ˈluv(ə)/, /ˈloːv(ə)/
love (plural loves)
Love; strong and deep affection:
Sexual or romantic desire (in humans and other animals)
Theosis, sanctification, or love as a means to attain it.
One who one loves; a loved individual:
A lover; a sexual or romantic partner.
A personification or embodiment of love.
(Christianity) The Holy Spirit (or less often, God generally).
A peace treaty; the ending of hostilities.
(rare) Permission, consent.
English: love
Scots: luve, lufe
Yola: loove
“lǒve, n.(1).”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007.
Inherited from Old English lāfe, oblique singular of lāf, from Proto-West Germanic *laibu, from Proto-Germanic *laibō; compare leven (“to halt”), which some forms are influenced by.
lave, leve, loove
lafe, læve, loave (Early Middle English)
IPA(key): /ˈlɔːv(ə)/
(Northern) IPA(key): /laːf/, /ˈlaːv(ə)/
love (uncountable)
The remainder or rest; that which is left.
(rare) A widow; a woman whose husband has died.
Synonyms: relicte, widwe
English: lave
Scots: lave
“lōve, n.(2).”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007.
Borrowed from Old Norse lófi, from Proto-Germanic *lōfô; compare glove.
lof, loove, louf, luf, lufe, luff, luffe
IPA(key): /ˈloːv(ə)/, /loːf/
love (plural loves)
(chiefly Northern) The palm (inner part of the hand)
English: loof
Scots: luif, lufe, luff
“lọ̄ve, n.(3).”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007.
love
Alternative form of loven (“to love”)
love
Alternative form of loven (“to praise”)
From Old Norse lofa.
love (imperative lov, present tense lover, simple past and past participle lova or lovet, present participle lovende)
to praise
love (imperative lov, present tense lover, simple past lova or lovet or lovte or lovde, past participle lova or lovet or lovt or lovd, present participle lovende)
to promise
(as an adjective) det lovede land - the Promised Land
løfte
“love” in The Bokmål Dictionary.
love (present tense lovar or lover, past tense lova or lovde, past participle lova or lovt or lovd, present participle lovande, imperative lov)
Alternative form of lova
love m (definite singular loven, indefinite plural lovar, definite plural lovane)
Alternative form of lóve
vole
love
plural of lovo
money
→ French: lové
→ Hungarian: lóvé
→ Romanian: lovea
→ Russian: лавэ́ (lavɛ́)
→ Scots: lowie
→ Serbo-Croatian:
Cyrillic script: ло́ва
Latin script: lóva
→ Slovak: lóve
love (Cyrillic spelling лове)
vocative singular of lov
love (Cyrillic spelling лове)
third-person plural present of loviti
love c
(chiefly in compounds) wrist (connecting the hand to the forearm)
handlov
love in Svensk ordbok (SO)
love in Svenska Akademiens ordbok (SAOB) | 166 |
788 | love | Love (wikipedia) | Love encompasses a range of strong and positive emotional and mental states, from the most sublime virtue or good habit, the deepest interpersonal affection, to the simplest pleasure. An example of this range of meanings is that the love of a mother differs from the love of a spouse, which differs from the love for food. Most commonly, love refers to a feeling of strong attraction and emotional attachment.
Love is considered to be both positive and negative, with its virtue representing human kindness, compassion, and affection—"the unselfish, loyal, and benevolent concern for the good of another"—and its vice representing a human moral flaw akin to vanity, selfishness, amour-propre, and egotism. It may also describe compassionate and affectionate actions towards other humans, oneself, or animals. In its various forms, love acts as a major facilitator of interpersonal relationships and, owing to its central psychological importance, is one of the most common themes in the creative arts. Love has been postulated to be a function that keeps human beings together against menaces and to facilitate the continuation of the species.
Ancient Greek philosophers identified six forms of love: familial love (storge), friendly love or platonic love (philia), romantic love (eros), self-love (philautia), guest love (xenia), and divine or unconditional love (agape). Modern authors have distinguished further varieties of love: fatuous love, unrequited love, empty love, companionate love, consummate love, infatuated love, amour de soi, and courtly love. Numerous cultures have also distinguished Ren, Yuanfen, Mamihlapinatapai, Cafuné, Kama, Bhakti, Mettā, Ishq, Chesed, Amore, charity, Saudade (and other variants or symbioses of these states), as culturally unique words, definitions, or expressions of love in regard to specified "moments" currently lacking in the English language.
The color wheel theory of love defines three primary, three secondary, and nine tertiary love styles, describing them in terms of the traditional color wheel. The triangular theory of love suggests intimacy, passion, and commitment are core components of love. Love has additional religious or spiritual meaning. This diversity of uses and meanings, combined with the complexity of the feelings involved, makes love unusually difficult to consistently define, compared to other emotional states.
== Definitions ==
The word "love" can have a variety of related but distinct meanings in different contexts. Many other languages use multiple words to express some of the different concepts that in English are denoted as "love"; one example is the plurality of Greek concepts for "love" (agape, eros, philia, storge). Cultural differences in conceptualizing love make it difficult to establish a universal definition.
Although the nature or essence of love is a subject of frequent debate, different aspects of the word can be clarified by determining what is not love (antonyms of "love"). Love, as a general expression of positive sentiment (a stronger form of like), is commonly contrasted with hate (or neutral apathy). As a less sexual and more emotionally intimate form of romantic attachment, love is commonly contrasted with lust. As an interpersonal relationship with romantic overtones, love is sometimes contrasted with friendship, although the word love is often applied to close friendships or platonic love. Further possible ambiguities come with usages like "girlfriend", "boyfriend", and "just good friends".
Abstractly discussed, love usually refers to a feeling one person experiences for another person. Love often involves caring for, or identifying with, a person or thing (cf. vulnerability and care theory of love), including oneself (cf. narcissism). In addition to cross-cultural differences in understanding love, ideas about love have also changed greatly over time. Some historians date modern conceptions of romantic love to courtly Europe during or after the Middle Ages, although the prior existence of romantic attachments is attested by ancient love poetry.
The complex and abstract nature of love often reduces its discourse to a thought-terminating cliché. Several common proverbs regard love, from Virgil's "Love conquers all" to The Beatles' "All You Need Is Love". St. Thomas Aquinas, following Aristotle, defines love as "to will the good of another." Bertrand Russell describes love as a condition of "absolute value," as opposed to relative value. Philosopher Gottfried Leibniz said that love is "to be delighted by the happiness of another." Meher Baba stated that in love there is a "feeling of unity" and an "active appreciation of the intrinsic worth of the object of love." Biologist Jeremy Griffith defines love as "unconditional selflessness". According to Ambrose Bierce, love is a temporary insanity curable by marriage.
== Impersonal ==
People can express love towards things other than humans; this can range from expressing a strong liking of something, such as "I love popcorn" or that something is essential to one's identity, such as "I love being an actor".
People can have a profound dedication and immense appreciation for an object, principle, or objective, thereby experiencing a sense of love towards it. For example, compassionate outreach and volunteer workers' "love" of their cause may sometimes be born not of interpersonal love but impersonal love, altruism, and strong spiritual or political convictions.
People can also "love" material objects, animals, or activities if they invest themselves in bonding or otherwise identifying with those things. If sexual passion is also involved, then this feeling is called paraphilia.
== Interpersonal ==
Interpersonal love refers to love between human beings. It is a much more potent sentiment than liking a person. Unrequited love refers to feelings of love that are not reciprocated. Interpersonal love is most closely associated with interpersonal relationships. Such love might exist between family members, friends, and couples. There are several psychological disorders related to love, such as erotomania.
Throughout history, philosophy and religion have speculated about the phenomenon of love. In the 20th century, the science of psychology has studied the subject. The sciences of anthropology, neuroscience, and biology have also added to the understanding of the concept of love.
=== Biological basis ===
Biological models of sex tend to view love as a mammalian drive, much like hunger or thirst. Helen Fisher, an anthropologist and human behavior researcher, divides the experience of love into three partly overlapping stages: lust, attraction, and attachment. Lust is the feeling of sexual desire; romantic attraction determines what partners find attractive and pursue, conserving time and energy by choosing; and attachment involves sharing a home, parental duties, mutual defense, and in humans involves feelings of safety and security. Three distinct neural circuitries, including neurotransmitters, and three behavioral patterns, are associated with these three romantic styles.
Lust is the initial passionate sexual desire that promotes mating, and involves the increased release of hormones such as testosterone and estrogen. These effects rarely last more than a few weeks or months. Attraction is the more individualized and romantic desire for a specific candidate for mating, which develops out of lust as commitment to an individual mate form. Recent studies in neuroscience have indicated that as people fall in love, the brain consistently releases a certain set of chemicals, including the neurotransmitter hormones dopamine, norepinephrine, and serotonin, the same compounds released by amphetamine, stimulating the brain's pleasure center and leading to side effects such as increased heart rate, reduced appetite and sleep, and an intense feeling of excitement. Research indicates that this stage generally lasts from one and a half to three years.
Since the lust and attraction stages are both considered temporary, a third stage is needed to account for long-term relationships. Attachment is the bonding that promotes relationships lasting for many years and even decades. Attachment is generally based on commitments such as marriage and children, or mutual friendship based on things like shared interests. It has been linked to higher levels of the chemicals oxytocin and vasopressin, to a greater degree than what is found in short-term relationships. Enzo Emanuele and coworkers reported the protein molecule known as the nerve growth factor (NGF) has high levels when people first fall in love, but these return to previous levels after one year.
=== Psychological basis ===
Psychology depicts love as a cognitive and social phenomenon. Psychologist Robert Sternberg formulated a triangular theory of love in which love has three components: intimacy, commitment, and passion. Intimacy is when two people share confidences and various details of their personal lives, and is usually shown in friendships and romantic love affairs. Commitment is the expectation that the relationship is permanent. Passionate love is shown in infatuation as well as romantic love. All forms of love are viewed as varying combinations of these three components. Non-love does not include any of these components. Liking only includes intimacy. Infatuated love only includes passion. Empty love only includes commitment. Romantic love includes both intimacy and passion. Companionate love includes intimacy and commitment. Fatuous love includes passion and commitment. Consummate love includes all three components.
American psychologist Zick Rubin sought to define love by psychometrics in the 1970s. His work identifies a different set of three factors that constitute love: attachment, caring, and intimacy.
Following developments in electrical theories such as Coulomb's law, which showed that positive and negative charges attract, analogs in human life were envisioned, such as "opposites attract". Research on human mating has generally found this not to be true when it comes to character and personality—people tend to like people similar to themselves. However, in a few unusual and specific domains, such as immune systems, it seems that humans prefer others who are unlike themselves (e.g., with an orthogonal immune system), perhaps because this will lead to a baby that has the best of both worlds.
In recent years, various human bonding theories have been developed, described in terms of attachments, ties, bonds, and affinities.
Some Western authorities disaggregate into two main components, the altruistic and the narcissistic. This view is represented in the works of Scott Peck, whose work in the field of applied psychology explored the definitions of love and evil. Peck maintains that love is a combination of the "concern for the spiritual growth of another" and simple narcissism. In combination, love is an activity, not simply a feeling.
Psychologist Erich Fromm maintained in his book The Art of Loving that love is not merely a feeling but is also actions, and that in fact the "feeling" of love is superficial in comparison to one's commitment to love via a series of loving actions over time. Fromm held that love is ultimately not a feeling at all, but rather is a commitment to, and adherence to, loving actions towards another, oneself, or many others, over a sustained duration. Fromm also described love as a conscious choice that in its early stages might originate as an involuntary feeling, but which then later no longer depends on those feelings, but rather depends only on conscious commitment.
=== Evolutionary basis ===
Evolutionary psychology has attempted to provide various reasons for love as a survival tool. Humans are dependent on parental help for a large portion of their lifespans compared to other mammals. Love has therefore been seen as a mechanism to promote parental support of children for this extended time period. Furthermore, researchers as early as Charles Darwin identified unique features of human love compared to other mammals and credited love as a major factor for creating social support systems that enabled the development and expansion of the human species. Another factor may be that sexually transmitted diseases can cause, among other effects, permanently reduced fertility, injury to the fetus, and increase complications during childbirth. This would favor monogamous relationships over polygamy.
=== Adaptive benefit ===
Interpersonal love between a man and woman provides an evolutionary adaptive benefit since it facilitates mating and sexual reproduction. However, some organisms can reproduce asexually without mating. Understanding the adaptive benefit of interpersonal love depends on understanding the adaptive benefit of sexual reproduction as opposed to asexual reproduction. Richard Michod reviewed evidence that love, and consequently sexual reproduction, provides two major adaptive advantages. First, sexual reproduction facilitates repair of damages in the DNA that is passed from parent to progeny (during meiosis, a key stage of the sexual process). Second, a gene in either parent may contain a harmful mutation, but in the progeny produced by sexual reproduction, expression of a harmful mutation introduced by one parent is likely to be masked by expression of the unaffected homologous gene from the other parent.
=== Comparison of scientific models ===
Biological models of love tend to see it as a mammalian drive, similar to hunger or thirst. Psychology sees love as more of a social and cultural phenomenon. Love is influenced by hormones (such as oxytocin), neurotrophins (such as NGF), and pheromones, and how people think and behave in love is influenced by their conceptions of love. The conventional view in biology is that there are two major drives in love: sexual attraction and attachment. Attachment between adults is presumed to work on the same principles that lead an infant to become attached to its mother. The traditional psychological view sees love as being a combination of companionate love and passionate love. Passionate love is intense longing, and is often accompanied by physiological arousal (shortness of breath, rapid heart rate); companionate love is affection and a feeling of intimacy not accompanied by physiological arousal.
=== Health ===
Love plays a role in human well-being and health. Engaging in activities associated with love, such as nurturing relationships, has been shown to activate key brain regions responsible for emotion, attention, motivation, and memory. These activities also contribute to the regulation of the autonomic nervous system, leading to stress reduction over time, although the initial stages of love may induce stress. Love's social bonds enhance both physical and mental health, fostering resilience, compassion, and closeness. It boosts immune function and promotes healing, while also encouraging positive motivations and behaviors for individual flourishing and survival. Breakups can evoke a range of emotional states, including distrust, rejection, and anger, leading to trauma and various psychological challenges such as anxiety, social withdrawal, and even love addiction. Individuals may become fixated on past relationships, perpetuating emotional distress akin to addiction. Health benefits grow bigger when married couples are older, this is because the partners play a crucial role in promoting each other's well-being. A loving relationship with God has significant impact on health.
== Cultural views ==
=== Ancient Greek ===
Greek distinguishes several different senses in which the word "love" is used. Ancient Greeks identified three main forms of love: friendship and/or platonic desire (philia), sexual and/or romantic desire (eros), and self-emptying or divine love (agape). Modern authors have distinguished further varieties of romantic love.
Agape (ἀγάπη agápē)
Agape, often a Christian term, denotes a form of love that stands apart from the conventional understanding of affection. Rooted in theological discourse, agape represents a love that is characterized by its spontaneous nature and its independence from the inherent value of its object. Originating from the Greek term for "love", agape has been examined within theological scholarship, particularly in contrast to eros. In the Christian tradition, agape is often attributed to the love of God for humanity, as well as humanity's reciprocal love for God and for one another, often termed as brotherly love. Agape is considered to be unmerited and unmotivated by any inherent worthiness in its recipient. Instead, it is portrayed as an expression of the nature of God, exemplifying divine love that transcends human comprehension.
Eros (ἔρως érōs)
Eros originally referred to a passionate desire, often synonymous with sexual passion, reflecting an egocentric nature. However, its modern interpretation portrays it as both selfish and responsive to the merits of the beloved, thus contingent on reasons. Plato, in his Symposium, argued that sexual desire, fixated on physical beauty, is inadequate and should evolve into an appreciation of the beauty of the soul, culminating in an appreciation of the form of beauty itself. In Greek mythology, Erossymbolizes the state of being in love, extending beyond mere physical sexuality (referred to as "Venus"). Unrestrained Venus can reduce individuals to mere appetite, but when Eros is present, the focus shifts to the beloved, elevating intimacy beyond physical gratification. Eros is depicted as divine yet potentially dangerous, capable of inspiring both altruism and selfishness.
Philia (φιλία philía)
Philia originally describing an affectionate regard or friendly feeling, extended to relationships like friendship, family members, business partners, and one's nation. Similar to eros, philia is often seen as responsive to positive attributes in the beloved. This similarity has led scholars to think whether the primary difference between romantic eros and philia lies solely in the sexual dimension of the former. The distinction between the two becomes more complex with attempts from scholars to diminish the importance of the sexual aspect in eros, contributing to a nuanced understanding of these forms of love. Philia was articulated by Aristotle in his Nicomachean Ethics. Aristotle suggests that philia can be motivated by considerations for either one's own benefit or the benefit of the other. Philia often arises from the utility found in the relationship or from admiration for the character or virtues of the other individual. Aristotle further elucidates that the foundation of philia rests on objective grounds; individuals must share similar dispositions, refrain from holding grudges, and embody qualities such as justice, among others.
=== Ancient Roman ===
In Latin, friendship was distinctly termed amicitia, while amor encompassed erotic passion, familial attachment, and, albeit less commonly, the affection between friends. Cicero, in his essay On Friendship reflects on the innate human tendency to both love oneself and seek out another with whom to intertwine minds, nearly blending them into a singular entity. This suggests that while friends remain distinct individuals, they also, in some sense, become intertwined, embodying a shared essence.
Lucretius perceives love as a disruptive and irrational force, leading to madness and despair. To him, it is an affliction distorting reality, a primal urge rooted in the biological need for species to propagate. He emphasizes love's futility and self-destructive nature. In contrast, Ovid acknowledges the pleasure of love alongside its risks and complexities. He views love as a game of manipulation and deception, marked by a blend of hedonism and cynicism. Ovid recognizes the transient nature of passion and the inevitable disappointment in romantic relationships.
=== Chinese ===
Ren (仁), a concept in Confucianism philosophy, embodying the essence of humanity and virtue. It is regarded as the sum of all virtues within a person, encompassing traits such as selflessness and self-cultivation. Ren emphasizes the cultivation of harmonious relationships within society, starting from the family unit and extending outward. Within Confucianism, these relationships are delineated by five main categories: father-son, older brother-younger brother, husband-wife, older friend-younger friend, and lord-servant. In Confucianism, one displays benevolent love by performing actions such as filial piety from children, kindness from parents, loyalty to the king and so forth.
Central to the concept of Ren is the notion of reciprocity and empathetic understanding. It is often interpreted as akin to love (愛, ài), but sometimes it also considered a stage between ài and ling, characterized by the sincere and open-hearted expression of human feelings. Through genuine love for others, individuals cultivate Ren and foster deeper connections that bridge the gap between the human and the divine. Ren's significance lies in its ability to foster genuine human connection and empathy, laying the foundation for harmonious relationships within society.
Mozi, a Chinese philosopher, articulated a philosophy centered on the principle of universal love. At the core of his teachings lay the belief that genuine harmony and societal well-being could only be achieved through love for others, transcending narrow self-interest. Mozi contended that universal love was not merely an abstract concept but a practical imperative, requiring individuals to actively promote the welfare of all members of society through their actions.
In Mozi's philosophical framework, universal love was not only a moral obligation but also a divine principle originating from Heaven itself. He argued that this principle was exemplified through the actions of sage-kings from ancient times, who demonstrated how love could manifest in tangible ways within human interactions. Mozi's advocacy for universal love extended beyond interpersonal relationships; he believed it should guide the selection of rulers and the structuring of society, emphasizing reciprocity and egalitarianism as foundational principles for a harmonious social order.
In Taoism, the concept of 慈 (ci) embodies compassion or love, with connotations of tender nurturing akin to a mother's care. It emphasizes the idea that creatures can only thrive through raising and nurturing. Ci serves as the wellspring of compassion or love that transcends preconceived notions of individuals, instead fostering compassion for people as they are. Love, as depicted in the Taoist text, Daodejing, is depicted as open and responsive to each person's unique circumstances. Taoism juxtaposes human beings with the vastness of nature, likening the creation of people to the formation of waves in the ocean. Unlike Confucianism, as portrayed in the Taoist text Zhuangzi, Taoist responses to the loss of a beloved may involve either mourning their passing or embracing the loss and finding joy in new creations. Daoist love seeks connections that surpass distinctions and superficial reflections.
=== Japanese ===
The Japanese language uses three words to convey the English equivalent of love — ai (愛), koi (恋 or 孤悲) and ren'ai (恋愛). The term ai carries a multiple meanings, encompassing feelings of feelings from superior to inferiors, compassion and empathy towards others and selfless love, originally referred to beauty and was often used in a religious context. Initially synonymous with koi, representing romantic love between a man and a woman, emphasizing its physical expression, ai underwent a transformation during the early Meiji era. It evolved into a euphemistic term for renbo (恋慕) or love attachment, signifying a shift towards a more egalitarian treatment and consideration of others as equals. Prior to Western influence, the term koi generally represented romantic love. Koi describes a longing for a member of the opposite sex and is typically interpreted as selfish and wanting. The term's origins come from the concept of lonely solitude as a result of separation from a loved one. Though modern usage of koi focuses on sexual love and infatuation, the Manyō used the term to cover a wider range of situations, including tenderness, benevolence, and material desire. The fusion of ai and koi gave rise to the modern term ren'ai; its usage more closely resembles that of koi in the form of romantic love.
The concept amae (甘え), the dependency and emotional bonds between an infant and its mother—a bond that lays the foundation for the archetypal concept of love. Japanese culture traditionally distinguishes between marriage and love, valuing practical considerations and complementarity within family units.
=== Indian ===
In ancient India, there was a understanding of erotics and the art of love. References in the Rigveda suggest the presence of romantic narratives in ancient Indo-Aryan society, evident in dialogues between deities like Yama and Yami, and Pururavas and Urvashi. The Sanskrit language, offered various terms to convey the concept of love, such as kama, sneha, priya, vatsalya, bhakti, priti and prema.
In Indian literature, there are seven stages of love. The first is preska, characterized by the desire to see something pleasant. Next is abhilasa, involving constant thoughts about the beloved. Then comes raga, signifying the mental inclination to be united with the beloved. Following that is shena, which involves favorable activities directed towards the beloved. Prema is the stage where one cannot live without the beloved. Then there is rati, which involves living together with the beloved. Finally, srngara represents the playful interaction with the beloved.
Kama initially representing desire and longing. Later, Vātsyāyana, the author of the Kama Sutra, explored the concept of kama, defining it as the enjoyment of sensory pleasures with conscious awareness. However, there were also teachings cautioning against becoming overly attached to desire, advocating for the pursuit of genuine happiness through transcending desires. The Atharvaveda, presents kama as the tender affection between partners.
Nevertheless, kama is also often associated with insatiable sexual desire intertwined with intense emotions like anger and greed, portraying it as potentially harmful. Over time, kama took on anthropomorphic qualities, evolving into the figure of the Indian Cupid.
Sneha, considered the emotional facet of love, stands in contrast to the intense passion of kama with its calm demeanor. Characterized by moisture and viscosity, the term originally denoted oiliness. It is often compounded with words for family members, reflecting attachment to individuals like mothers, fathers, and sons. Those experiencing sneha tend to exhibit great concern for one another. While traditionally attributed to sensing, the Harshacharita presents a spontaneous perspective, suggesting it lacks a definitive cause. Due to its emotional nature, sneha is transient, emerging without reason and disappearing likewise.
Preman represents a heightened stage in the development of love, characterized by the unbearable feeling of separation from the beloved. Etymologically, it denotes the sense of endearment akin to one's own. Priti, similar to preman, denotes fondness for anything delightful and familiar. It encompasses a general liking for arts, sports, and objects, while also encompassing a human instinct. Priti is built on foundations of trust and fidelity. Friendly relations (priti) may persist between individuals but are not necessarily bound by affection (sneha).
Vatsalya originally signifies the tender affection exhibited by a cow towards her calf, extending to denote the love nurtured by elders or superiors towards the younger or inferior. This love is exemplified in the affection of parents towards their children, a husband's care for his wife, or a ruler's concern for their subjects. Conversely, bhakti denotes the love expressed by the younger towards the seniors, exemplified in a child's devotion to their parents.
=== Persian ===
Interpretations of Rumi's poetry and Sufi cosmology by scholars emphasize a divine-centric perspective, focusing on the transcendent nature of love. These interpretations emphasize Rumi's rejection of mortal attachments in favor of a love for the ultimate beloved, seen as embodying absolute beauty and grandeur. Scholars like William Chittick assert that all love stems from the divine, with God being both lover and beloved. Leonard Lewisohn characterizes Rumi's poetry as part of a mystical tradition that celebrates love as pathways to union with the divine, highlighting a transcendent experience.
In Persian mysticism, the concept of creation stems from love, viewed as the fundamental essence from which all beings originate and to which they ultimately return. This notion, influenced by neoplatonism, portrays love as both earthly and transcendent, embodying a universal striving for reunion with the divine. Scholars such as Abdolhossein Zarrinkoob trace this philosophical stance, highlighting its fusion with ancient Persian religious beliefs in figures like Ibn Arabi. According to Islamicists like William Chittick and Leonard Lewisohn, all forms of love find their origin in divine love, with creation serving as a reflection of God's beauty and love. This perspective is evident in the poetry of Hafez and others, where the concept of tajalli, or divine self-manifestation, underscores the profound spiritual significance of love as it pertains to both human relationships and devotion to God.
== Religious views ==
=== Abrahamic ===
==== Judaism ====
In Hebrew, אהבה (ahavah) signifies the love of Israelites for God and each other. However, the concept hesed offers a deeper understanding of love within Jewish thought and life. It goes beyond mere passion, embodying a character trait that is actively expressed through generosity and grace. Hesed has a dual nature: when attributed to God, it denotes grace or favor, while when practiced by humans, it reflects piety and devotion.
Hasidim, demonstrate their commitment and love for God through acts of hesed. The Torah serves as a guide, outlining how Israelites should express their love for God, show reverence for nature, and demonstrate compassion toward fellow human beings. The commandment "Love thy neighbor as thyself" from the Torah's, gives emphasis on ethical obligations and impartiality in judgment. It highlights the importance of treating all individuals equally before the law, rejecting favoritism and bribery; deuteronomy further emphasizes impartiality in judgment.
As for love between marital partners, this is deemed an essential ingredient to life: "See life with the wife you love" (Ecclesiastes 9:9). Rabbi David Wolpe writes that "love is not only about the feelings of the lover... It is when one person believes in another person and shows it." He further states that "love... is a feeling that expresses itself in action. What we really feel is reflected in what we do." The biblical book Song of Solomon is considered a romantically phrased metaphor of love between God and his people, but in its plain reading it reads like a love song. The 20th-century rabbi Eliyahu Eliezer Dessler is frequently quoted as defining love from the Jewish point of view as "giving without expecting to take".
==== Christianity ====
The Christian understanding is that love comes from God, who is himself love (1 John 4:8). The love of man and woman—eros in Greek—and the unselfish love of others (agape), are often contrasted as "descending" and "ascending" love, respectively, but are ultimately the same thing.
There are several Greek words for "love" that are regularly referred to in Christian circles.
agape
In the New Testament, agapē is charitable, selfless, altruistic, and unconditional. It is parental love, seen as creating goodness in the world; it is the way God is seen to love humanity, and it is seen as the kind of love that Christians aspire to have for one another.
phileo
Also used in the New Testament, phileo is a human response to something that is found to be delightful. Also known as "brotherly love."
Two other words for love in the Greek language, eros (sexual love) and storge (child-to-parent love), were never used in the New Testament.
Christians believe that to love God with all your heart, mind, and strength and love your neighbor as yourself are the two most important things in life (the greatest commandment of the Jewish Torah, according to Jesus; cf. Gospel of Mark 12:28–34). Saint Augustine summarized this when he wrote "Love God, and do as thou wilt."
The Apostle Paul glorified love as the most important virtue of all. Describing love in the famous poetic interpretation in 1 Corinthians, he wrote, "Love is patient, love is kind. It does not envy, it does not boast, it is not proud. It is not rude, it is not self-seeking, it is not easily angered, it keeps no record of wrongs. Love does not delight in evil but rejoices with the truth. It always protects, always trusts, always hopes, and always perseveres." (1 Corinthians 13:4–7)
The Apostle John wrote, "For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. For God did not send his Son into the world to condemn the world, but to save the world through him." (John 3:16–17) John also wrote, "Dear friends, let us love one another for love comes from God. Everyone who loves has been born of God and knows God. Whoever does not love does not know God, because God is love." (1 John 4:7–8)
Saint Augustine wrote that one must be able to decipher the difference between love and lust. Lust, according to Saint Augustine, is an overindulgence, but to love and be loved is what he has sought for his entire life. He even says, "I was in love with love." Finally, he does fall in love and is loved back, by God. Saint Augustine says the only one who can love you truly and fully is God, because love with a human only allows for flaws such as "jealousy, suspicion, fear, anger, and contention.": III.1 According to Saint Augustine, to love God is "to attain the peace which is yours.": X.27
Augustine regards the duplex commandment of love in Matthew 22 as the heart of Christian faith and the interpretation of the Bible. After the review of Christian doctrine, Augustine treats the problem of love in terms of use and enjoyment until the end of Book I of De Doctrina Christiana (1.22.21–1.40.44).
Christian theologians see God as the source of love, which is mirrored in humans and their own loving relationships. Influential Christian theologian C. S. Lewis wrote a book called The Four Loves. Benedict XVI named his first encyclical God is love. He said that a human being, created in the image of God, who is love, is able to practice love; to give himself to God and others (agape) and by receiving and experiencing God's love in contemplation (eros). This life of love, according to him, is the life of the saints such as Teresa of Calcutta and Mary, the mother of Jesus and is the direction Christians take when they believe that God loves them.
Pope Francis asserts that the "Cross (Jesus crucified) is the greatest meaning of the greatest love," and in the crucifixion is found everything, all knowledge and the entirety of God's love. Pope Francis taught that "True love is both loving and letting oneself be loved... what is important in love is not our loving, but allowing ourselves to be loved by God." And so, in the analysis of a Catholic theologian, for Pope Francis, "the key to love... is not our activity. It is the activity of the greatest, and the source, of all the powers in the universe: God's."
In Christianity the practical definition of love is summarized by Thomas Aquinas, who defined love as "to will the good of another," or to desire for another to succeed. This is an explanation of the Christian need to love others, including their enemies. Thomas Aquinas explains that Christian love is motivated by the need to see others succeed in life, to be good people.
Regarding love for enemies, Jesus is quoted in the Gospel of Matthew:
You have heard that it was said, "Love your neighbor and hate your enemy." But I tell you, love your enemies and pray for those who persecute you, that you may be children of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. If you love those who love you, what reward will you get? Are not even the tax collectors doing that? And if you greet only your own people, what are you doing more than others? Do not even pagans do that? Be perfect, therefore, as your heavenly Father is perfect.
Tertullian wrote regarding love for enemies: "Our individual, extraordinary, and perfect goodness consists in loving our enemies. To love one's friends is common practice, to love one's enemies only among Christians."
==== Islam ====
Love encompasses the Islamic view of life as universal brotherhood that applies to all who hold faith. Among the 99 names of God (Allah) is the name Al-Wadud, or "the Loving One," which is found in Surah 11:90 and 85:14. God is also referenced at the beginning of every chapter in the Qur'an as Ar-Rahman and Ar-Rahim, or the "Most Compassionate" and the "Most Merciful", indicating that nobody is more loving, compassionate, and benevolent than God. The Qur'an refers to God as being "full of loving kindness."
The Qur'an exhorts Muslim believers to treat all people, those who have not persecuted them, with birr or "deep kindness" as stated in Surah 6:8-9. Birr is also used by the Qur'an to describe the love and kindness that children must show to their parents.
Ishq, or divine love, is emphasized by Sufism in the Islamic tradition. Practitioners of Sufism believe that love is a projection of the essence of God into the universe. God desires to recognize beauty, and as if one looks at a mirror to see oneself, God "looks" at himself within the dynamics of nature. Since everything is a reflection of God, the school of Sufism practices seeing the beauty inside the apparently ugly. Sufism is often referred to as the religion of love. God in Sufism is referred to in three main terms—Lover, Loved, and Beloved—with the last of these terms often seen in Sufi poetry. A common viewpoint of Sufism is that through love, humankind can return to its inherent purity and grace. The saints of Sufism are infamous for being "drunk" due to their love of God; hence, the constant reference to wine in Sufi poetry and music.
==== Bahá'í Faith ====
The Bahá'í concept of the human soul emphasizes its expression through capacities such as knowledge, love, and will. According to Bahá'í teachings, conscious recognition of one's Creator and a reciprocal love relationship with that Creator form the basis of obedience to religious law. This perspective grounds adherence to law within the spiritual dynamics of each individual's journey, portraying obedience as a conscious choice driven by love rather than as mere compliance with external dictates.
Baháʼu'lláh, the founder of the Bahá'í Faith, emphasizes the importance of observing God's commandments out of love, describing them as "the lamps of My loving providence" and urging followers to adhere to them for "the love of My beauty." This framing positions love as the motive force for individuals striving to follow divine laws. In Bahá'í understanding, love is considered the fundamental universal law. ʻAbdu'l-Bahá, Bahá'u'lláh's son and successor, describes love as the "most great law" and the force that binds together the diverse elements of the material world. He further asserts that love is the establisher of true civilization and the source of glory for every race and nation.
From the Bahá'í perspective, God's revelation of laws to humanity is an act of love, and the legitimate reason for their application and adherence lies in their expression of love. This understanding underscores the intimate connection between spiritual principles, individual growth, and the practice of religious law within the Bahá'í Faith.
=== Dharmic ===
==== Buddhism ====
In Buddhism, kāma is sensuous, sexual love. It is an obstacle on the path to enlightenment, since it is selfish. Karuṇā is compassion and mercy, which reduces the suffering of others. It is complementary to wisdom and is necessary for enlightenment. Adveṣa and mettā are benevolent love. This love is unconditional and requires considerable self-acceptance. This is quite different from ordinary love, which is usually about attachment and sex and which rarely occurs without self-interest. Instead, in Buddhism love refers to detachment and unselfish interest in others' welfare.
The Bodhisattva ideal in Mahayana Buddhism involves the complete renunciation of oneself in order to take on the burden of a suffering world.
==== Hinduism ====
In Hinduism, kāma is pleasurable, sexual love, personified by the god Kamadeva. For many Hindu schools, it is the third end (Kama) in life. Kamadeva is often pictured holding a bow of sugar cane and an arrow of flowers; he may ride upon a great parrot. He is usually accompanied by his consort Rati and his companion Vasanta, lord of the spring season. Stone images of Kamadeva and Rati can be seen on the door of the Chennakeshava Temple, Belur, in Karnataka, India. Maara is another name for kāma.
In contrast to kāma, prema—or prem refers to "elevated" love. Karuṇā is compassion and mercy, which impels one to help reduce the suffering of others. Bhakti is a Sanskrit term meaning "loving devotion to the divine." A person who practices bhakti is called a bhakta. Hindu writers, theologians, and philosophers have distinguished nine forms of bhakti, which can be found in the Bhagavata Purana and works by Tulsidas. The philosophical work Narada Bhakti Sutra, written by an unknown author (presumed to be Narada), distinguishes eleven forms of love.
In certain Vaishnava sects within Hinduism, attaining unadulterated, unconditional, and incessant love for the Godhead is considered the foremost goal of life. Gaudiya Vaishnavas, who worship Krishna as the Supreme Personality of Godhead and the cause of all causes, consider Love for Godhead, (Prema), to act in two ways: sambhoga and vipralambha (union and separation)—two opposites.
In the condition of separation, there is an acute yearning for being with the beloved and in the condition of union, there is supreme happiness. Gaudiya Vaishnavas consider that Krishna-prema (love for Godhead) burns away one's material desires, pierces the heart, and washes away everything—one's pride, one's religious rules, and one's shyness. Krishna-prema is considered to make one drown in the ocean of transcendental ecstasy and pleasure. The love of Radha, a cowherd girl, for Krishna is often cited as the supreme example of love for Godhead by Gaudiya Vaishnavas. Radha is considered to be the internal potency of Krishna, and is the supreme lover of Godhead. Her example of love is considered to be beyond the understanding of the material realm, as it surpasses any form of selfish love or lust that is visible in the material world. The reciprocal love between Radha (the supreme lover) and Krishna (God as the Supremely Loved) is the subject of many poetic compositions in India, such as the Gita Govinda of Jayadeva and Hari Bhakti Shuddhodhaya.
In the Bhakti tradition within Hinduism, it is believed that execution of devotional service to God leads to the development of Love for God (taiche bhakti-phale krsne prema upajaya), and as love for God increases in the heart, the more one becomes free from material contamination (krishna-prema asvada haile, bhava nasa paya). Being perfectly in love with God or Krishna makes one perfectly free from material contamination, and this is the ultimate way of salvation or liberation. In this tradition, salvation or liberation is considered inferior to love, and just an incidental by-product. Being absorbed in Love for God is considered to be the perfection of life.
== Political views ==
=== Free love ===
The term "free love" has been used to describe a social movement that rejects marriage, which is seen as a form of social bondage. The free love movement's initial goal was to separate the state from sexual matters such as marriage, birth control, and adultery. It claimed that such issues were the concern of the people involved, and no one else.
Many people in the early 19th century believed that marriage was an important aspect of life to "fulfill earthly human happiness." Middle-class Americans wanted the home to be a place of stability in an uncertain world. This mentality created a vision of strongly defined gender roles, which provoked the advancement of the free love movement as a contrast.
Advocates of free love had two strong beliefs: opposition to the idea of forceful sexual activity in a relationship and advocacy for a woman to use her body in any way that she pleases. These are also beliefs of feminism.
== Philosophical views ==
Philosophically, there four types of love that are distinguished: love as a union; love as robust concern; love as valuing; and love as an emotion. Love as a union suggests that love involves the formation of a union between the two individuals, creating a "we". Roger Scruton and Mark Fisher emphasize the union of concerns, where the distinction between the lover's different interests dissapears and a new shared care and concern emerges. Robert C. Solomon views love as a literal fusion between the two individuals, resulting in a shared identity and mutual definition. Robert Nozick argues that love creates a new "we" through the pooling of well-being and autonomy, as well as the adoption of a joint identity. Critics argue that love as a union undermines individual autonomy and the lovers become unintelligible. However, Nozick and Fisher claim that this loss is a desirable aspect of love. Michael Friedman proposes a federation model, where love creates a new unified entity without erasing individual identities, thus allowing for the concern for the beloved's sake.
Love as a robust concern posits that love is primarily defined by caring about the beloved's sake, without creating a "we" or any type of union between the lovers. This perspective emphasizes the willing aspect of love, where one's desire and motivations are shaped by concern for the beloved's well-being. Critics of this view argue that the definition is too passive, in the sense that the conception of the beloved overlooks the interactive nature of love, as well as the emotional responsiveness to the beloved. However, defenders argue that promoting the beloved's well-being requires respecting their autonomy and emotional responses. Furthermore, critics claim that the robust concern focus solely on desires and concerns for the beloved's welfare, making it too strict of a definition. Defenders counter that the desire for the beloved's well being is an essential aspect to love. Monique Wonderly suggests that the concept of attachment can complement the robust concern view, capturing the idea that the beloved is not only important for their own sake but also to the lover.
Love as valuing has two main approaches: love as appraisal of value and love as bestowal of value. J. David Velleman proposes that the former involves acknowledging and responding uniquely to the value of the beloved. Kantian distinctions are drawn between dignity and price, dignity being that the value of something is not comparable, and price being that it is comparable; thus people possess dignity due to their rational nature. Love, on this view, responds to the dignity of persons, but it differs from respect in that it disarms emotional defenses, making one vulnerable to the beloved. However, critics argue that Velleman's account struggles to explain the selectivity and constancy of love, as well as the role of emotions in appraisal. Peter Singer claims that love as a bestowal of value involves bestowing intrisic value upon the beloved. Unlike appraisal, which responds to pre-existing value, bestowal creates value in the beloved. Singer argues that love is non-teleological and cannot be justified, but rather involves attachment and commitment to the beloved. However, critics question how bestowal accounts for the selectivity of love and its discerning nature.
Finally, love as an emotion is divided in two perspectives: love as emotion proper and love as emotion complex. The former sees love as a particular motivational response to an object, similar to other emotions. However, critics argue that defining love solely as an emotion oversimplifies its nature. James Robert Brown suggests that love evaluates the beloved as worthwhile, but this perspective fails to capture the complexity of love compared to other evaluative responses like admiration or respect, according to critics. Love as emotion complex understands love as a complex emotional attitude towards another person, involving historical patterns concerning of one's emotional responsiveness to the beloved. It emphasizes the dynamic nature of love, where ther lover's identity is continually transformed by loving the beloved. Emotional responses are interconnected and tied to the historical narrative of the relationship. Annette Baier and Neera K. Badhwar emphasize emotional interdependence, while Paul Helm suggests that love involves intimate identification, where sharing the values of the beloved is central. Critics argue that these views do not answer how to distinguish loving relationship from other relationships and what constitues the characteristic narrative history of love.
== Literature depictions ==
== See also ==
Color wheel theory of love – Idea created by psychologist John Alan LeePages displaying short descriptions of redirect targets
Finger heart – Hand gesture
Hand heart – Affectionate hand gesture
Heart in hand – Symbol of charity
Human bonding – Process of development of a close, interpersonal relationship
ILY sign – American Sign Language gesture
Love at first sight – Falling in long-lasting love with someone on first sight
Love-in – Peaceful public gatheringPages displaying wikidata descriptions as a fallback
Pair bond – Biological term
Polyamory – Intimacy for multiple partners
Relationship science – Field dedicated to the scientific study of interpersonal relationship processes
Romance (love) – Type of love that focuses on feelings
Self-love – Concept in philosophy and psychology
Social connection – Term in psychology referring to the experience of feeling close and connected to others
Traditional forms, Agape, Philia, Philautia, Storge, Eros: Greek terms for love
== References ==
== Sources ==
== Further reading ==
Bayer, A, ed. (2008). Art and love in Renaissance Italy. New York: The Metropolitan Museum of Art.
== External links ==
History of Love, Internet Encyclopedia of Philosophy
Friendship at Curlie
Philanthropy at Curlie
Romance at Curlie | Love encompasses a range of strong and positive emotional and mental states, from the most sublime virtue or good habit, the deepest interpersonal affection, to the simplest pleasure. An example of this range of meanings is that the love of a mother differs from the love of a spouse, which differs from the love for food. Most commonly, love refers to a feeling of strong attraction and emotional attachment.
Love is considered to be both positive and negative, with its virtue representing human kindness, compassion, and affection—"the unselfish, loyal, and benevolent concern for the good of another"—and its vice representing a human moral flaw akin to vanity, selfishness, amour-propre, and egotism. It may also describe compassionate and affectionate actions towards other humans, oneself, or animals. In its various forms, love acts as a major facilitator of interpersonal relationships and, owing to its central psychological importance, is one of the most common themes in the creative arts. Love has been postulated to be a function that keeps human beings together against menaces and to facilitate the continuation of the species.
Ancient Greek philosophers identified six forms of love: familial love (storge), friendly love or platonic love (philia), romantic love (eros), self-love (philautia), guest love (xenia), and divine or unconditional love (agape). Modern authors have distinguished further varieties of love: fatuous love, unrequited love, empty love, companionate love, consummate love, infatuated love, amour de soi, and courtly love. Numerous cultures have also distinguished Ren, Yuanfen, Mamihlapinatapai, Cafuné, Kama, Bhakti, Mettā, Ishq, Chesed, Amore, charity, Saudade (and other variants or symbioses of these states), as culturally unique words, definitions, or expressions of love in regard to specified "moments" currently lacking in the English language.
The color wheel theory of love defines three primary, three secondary, and nine tertiary love styles, describing them in terms of the traditional color wheel. The triangular theory of love suggests intimacy, passion, and commitment are core components of love. Love has additional religious or spiritual meaning. This diversity of uses and meanings, combined with the complexity of the feelings involved, makes love unusually difficult to consistently define, compared to other emotional states. | 13 |
789 | love | Love (1919 German film) (wikipedia) | Love (German: Liebe) is a 1919 German silent film directed by Manfred Noa and starring Reinhold Schünzel and Tzwetta Tzatschewa.
The film's sets were designed by the art director Karl Machus.
== Plot ==
== Cast ==
Reinhold Schünzel as Herbert Warfield
Tzwetta Tzatschewa as Dorothy Hall
Jeanette Bethge as Garderobiere
Bruno Harprecht as James Illing
Karl Platen as Erster Sekretär bei Illing
Fritz Richard as Flüchtling Alvadres
Heinz Sarnow as Robert
== References ==
== Bibliography ==
Bock, Hans-Michael & Bergfelder, Tim. The Concise CineGraph. Encyclopedia of German Cinema. Berghahn Books, 2009.
== External links ==
Love at IMDb | Love (German: Liebe) is a 1919 German silent film directed by Manfred Noa and starring Reinhold Schünzel and Tzwetta Tzatschewa.
The film's sets were designed by the art director Karl Machus. | 1 |
790 | love | Love (1927 American film) (wikipedia) | Love is a 1927 American silent drama film directed by Edmund Goulding and released by Metro-Goldwyn-Mayer. A sound version of the film was released in 1928 with a synchronized musical score with sound effects. MGM made the film to capitalize on its winning romantic team of Greta Garbo and John Gilbert who had starred in the 1926 blockbuster Flesh and the Devil.
Taking full advantage of the star power, a drama was scripted based on Leo Tolstoy's 1877 novel, Anna Karenina. The result was a failure for the author's purists, but it provided the public with a taste of Gilbert-Garbo eroticism that would never again be matched. The publicity campaign for the film was one of the largest up to that time, and the title was changed from the original, Heat.
Director Dimitri Buchowetzki began work on Love with Garbo and Ricardo Cortez. However, producer Irving Thalberg was unhappy with the early filming, and started over by replacing Buchowetzki with Edmund Goulding, cinematographer Merritt B. Gerstad with William H. Daniels, and Cortez with Gilbert.
== Music ==
The 1928 sound version featured a theme song entitled "That Melody Of Love" which was composed by Walter Donaldson and Howard Dietz. Ernst Luz was responsible for the arrangement of the musical score for the sound version of the film.
== Plot ==
During a blizzard, Russian count Alexis Vronsky, aide-de-camp of the Grand Duke, meets a veiled woman on the way to St. Petersburg, Russia. When they are forced to stop at an inn overnight, Vronsky attempts to seduce her but she rejects him.
Later, at a reception for Senator Karenin, Vronsky is presented to the Senator's wife, Anna, who is the woman at the inn, and asks forgiveness for his transgression. This she finally grants. She is determined to avoid him and temptation, but boredom with an older husband leads her to see Vronsky again and a relationship develops.
Anna has a young son, Sergei, with whom she has an extremely close relationship which thaws as the passion develops between Anna and Vronsky. This passion is noted by the aristocracy, to the displeasure of her husband. After a horse race, in which Anna demonstrates publicly her excessive interest in Vronsky's safety, she visits Vronsky in his rooms to see that he is all right and is cast off by her husband. Anna and Vronsky go off to Italy together.
After a while, Anna suffers because she left her son, so Vronsky takes her back to Russia. She visits her son, who had been told she was dead. Anna brings him presents on his birthday, but she is discovered by Karenin and barred from the house permanently. He tells Anna that her son will forget her, as he has done once already, and that her death would be better than the dishonor she will bring on him. He also tells her that the Grand Duke plans to cashier Vronsky from his regiment, ending a long and honourable family tradition of elite army service, because he is cohabitating with Anna. She begs the Grand Duke for mercy and succeeds in persuading him to relent on the condition that she leaves St. Petersberg and never sees Vronsky again. While he is at the dinner to which the Grand Duke has summoned him, she departs.
=== Alternate ending (European version) ===
As a result of being unable to see her son and having to leave Vronsky, she commits suicide by leaping in front of a train. This variant follows the original work of Leo Tolstoy.
=== Alternate ending (American version) ===
For three years, the lovers do not see each other but Vronsky searches frantically for Anna. By chance, he reads in a newspaper that Anna's son is at the Military Academy in St. Petersburg and visits him, learning that Karenin has died and that Anna visits her son daily. They meet and are reunited.
(American exhibitors were given the choice of whether or not to use the revised "happy" ending. Theaters on the coasts mostly picked Tolstoy while theaters in Middle America mostly picked the happy ending.)
== Cast ==
John Gilbert as Captain Count Alexei Vronsky
Greta Garbo as Anna Karenina
George Fawcett as Grand Duke Michael
Emily Fitzroy as Grand Duchess
Brandon Hurst as Senator Alexei Karenin
Philippe De Lacy as Serezha Karenin, Anna's Child
Edward Connelly as Priest (uncredited)
Carrie Daumery as Dowager (uncredited)
Margaret Lee as Blonde Flirt (uncredited)
Dorothy Sebastian as Spectator Extra at Races (uncredited)
Jacques Tourneur as Extra (uncredited)
== Release and reception ==
According to MGM records Love earned $946,000 in theater rentals from the United States and Canada and an additional $741,000 from foreign rentals, giving the studio a profit of $571,000.
== References ==
== External links ==
Love at the AFI Catalog of Feature Films
Love at IMDb
Love is available for free viewing and download at the Internet Archive
Love at AllMovie
Love at the TCM Movie Database | Love is a 1927 American silent drama film directed by Edmund Goulding and released by Metro-Goldwyn-Mayer. A sound version of the film was released in 1928 with a synchronized musical score with sound effects. MGM made the film to capitalize on its winning romantic team of Greta Garbo and John Gilbert who had starred in the 1926 blockbuster Flesh and the Devil.
Taking full advantage of the star power, a drama was scripted based on Leo Tolstoy's 1877 novel, Anna Karenina. The result was a failure for the author's purists, but it provided the public with a taste of Gilbert-Garbo eroticism that would never again be matched. The publicity campaign for the film was one of the largest up to that time, and the title was changed from the original, Heat.
Director Dimitri Buchowetzki began work on Love with Garbo and Ricardo Cortez. However, producer Irving Thalberg was unhappy with the early filming, and started over by replacing Buchowetzki with Edmund Goulding, cinematographer Merritt B. Gerstad with William H. Daniels, and Cortez with Gilbert. | 7 |
791 | love | Love (1927 German film) (wikipedia) | Love (German: Liebe) is a 1927 German silent film directed by Paul Czinner and starring Elisabeth Bergner, Agnes Esterhazy and Elza Temary.
== Plot ==
== Cast ==
Elisabeth Bergner as Herzogin von Langeais
Agnes Esterhazy as Gräfin Serezy
Elza Temary as Gräfin Fontaine
Olga Engl as Die alte Prinzessin
Else Heller as Äbtissin
Hans Rehmann as Marquis von Montriveau
Paul Otto as Marquis von Ronquerolles
Nicolai Wassiljeff as Der junge Prinz
Arthur Kraußneck as Vitzdom von Pamier
Leopold von Ledebur as Herzog von Navarra
Jaro Fürth as Herzog von Grandlieu
Hans Conrady as Ein Mönch
Karl Platen as Diener
== References ==
== Bibliography ==
Eisner, Lotte H. The Haunted Screen: Expressionism in the German Cinema and the Influence of Max Reinhardt. University of California Press, 2008.
== External links ==
Love at IMDb
Love at AllMovie | Love (German: Liebe) is a 1927 German silent film directed by Paul Czinner and starring Elisabeth Bergner, Agnes Esterhazy and Elza Temary. | 0 |
792 | love | Love (1956 film) (wikipedia) | Love (German: Liebe, Italian: Uragano sul Po) is a 1956 West German-Italian drama film directed by Horst Hächler and starring Maria Schell, Raf Vallone and Eva Kotthaus. It is an adaptation of the 1951 novel Vor Rehen wird gewarnt by Vicki Baum.
The film's sets were designed by the art director Rolf Zehetbauer. It was shot at the Spandau Studios in Berlin. Location shooting took place in Venice and along the Po River.
== Synopsis ==
Anna falls madly in love with an Italian violinist, who instead marries her sister Monika.
== Cast ==
Maria Schell as Anna Ballard
Raf Vallone as Andrea Ambaros
Eva Kotthaus as Monika Ballard
Camilla Spira as Frau Ballard
Fritz Tillmann as Herr Ballard
Peter Carsten as Jan Hopper
Ave Ninchi as Beatrice
Elke Aberle as Lorella
Werner Schott as Arzt
Wolfgang Jansen as Gärtnerjunge Kurt
== References ==
== Bibliography ==
Bock, Hans-Michael & Bergfelder, Tim. The Concise CineGraph. Encyclopedia of German Cinema. Berghahn Books, 2009.
== External links ==
Love at IMDb
Love at AllMovie
Love at Variety Distribution | Love (German: Liebe, Italian: Uragano sul Po) is a 1956 West German-Italian drama film directed by Horst Hächler and starring Maria Schell, Raf Vallone and Eva Kotthaus. It is an adaptation of the 1951 novel Vor Rehen wird gewarnt by Vicki Baum.
The film's sets were designed by the art director Rolf Zehetbauer. It was shot at the Spandau Studios in Berlin. Location shooting took place in Venice and along the Po River. | 4 |
793 | love | Love (1971 film) (wikipedia) | Love (Hungarian: Szerelem) is a 1971 Hungarian drama film directed by Károly Makk. Based on two short stories by Tibor Déry, Szerelem (1956) and Két asszony (1962), it stars Lili Darvas and Mari Törőcsik. The film was selected as the Hungarian entry for the Best Foreign Language Film at the 44th Academy Awards, but was not accepted as a nominee.
Today, Love is considered a classic of world cinema by critics including Derek Malcolm and Roger Ebert. The film was selected for screening as part of the Cannes Classics section at the 2016 Cannes Film Festival. It was also chosen to be part of the New Budapest Twelve, a list of Hungarian films considered the best in 2000.
== Plot ==
== Cast ==
Lili Darvas - Az öregasszony
Mari Törőcsik - Luca
Iván Darvas - János
Erzsi Orsolya - Irén
László Mensáros - Az orvos
Tibor Bitskey - Feri (as Bitskei Tibor)
András Ambrus - Börtönőr
József Almási - Tanár
Zoltán Bán - Borbély
Éva Bányai - Feriék szolgálója
Ágnes Dávid - Feriék szolgálója
Mária Garamszegi - Feriék szolgálója
Alíz Halda - Tanárnő
Magda Horváth - Kissné
Nóra Káldi - Az öregasszony fiatalon (as Káldy Nóra)
== Historical background ==
In 1953 after the death of Soviet premier Joseph Stalin many arrested people were released in Hungary. In Love, Makk tells the story of a young Hungarian woman whose husband has been arrested by the secret police, and who eases his mother's last months with the tale that her son is in America.
== Reception ==
Love won three prizes, including the Jury Prize at the 1971 Cannes Film Festival. It has also been acclaimed in recent years; Derek Malcolm ranked it one of The Guardian's 100 best films of the 20th century.
== See also ==
List of submissions to the 44th Academy Awards for Best Foreign Language Film
List of Hungarian submissions for the Academy Award for Best Foreign Language Film
== References ==
== External links ==
Love at IMDb
Love at AllMovie | Love (Hungarian: Szerelem) is a 1971 Hungarian drama film directed by Károly Makk. Based on two short stories by Tibor Déry, Szerelem (1956) and Két asszony (1962), it stars Lili Darvas and Mari Törőcsik. The film was selected as the Hungarian entry for the Best Foreign Language Film at the 44th Academy Awards, but was not accepted as a nominee.
Today, Love is considered a classic of world cinema by critics including Derek Malcolm and Roger Ebert. The film was selected for screening as part of the Cannes Classics section at the 2016 Cannes Film Festival. It was also chosen to be part of the New Budapest Twelve, a list of Hungarian films considered the best in 2000. | 5 |
794 | love | Love (1991 Indian film) (wikipedia) | Love is a 1991 Indian Hindi-language romance film directed by Suresh Krissna, starring Salman Khan, Revathi (in her Bollywood debut) in the lead roles. It is the remake of the Telugu film Prema (1989). It could not repeat the success of the original and ended up as an average grosser. The makers changed the tragic climax from the original film to one with a happy ending. This movie is also remembered for the romantic song "Saathiya Tune Kya Kiya". The rights to this film are owned by Shah Rukh Khan's Red Chillies Entertainment.
== Plot ==
Jailed as a juvenile for killing his abusive father (Sudhir Kumar), who is responsible for his mother's suicide, Prithvi (Salman Khan) is unable to stand any atrocity. He meets Maggie Pinto (Revathi Menon) and after a few chance meetings, they both fall in love. Maggie takes Prithvi to meet her parents, but they reject him after learning about his criminal past. When Maggie and Prithvi persist, Maggie's mother, Stella Pinto (Rita Bhaduri), calls the police and has Prithvi jailed. Guruji (Amjad Khan) comes to Prithvi's aid and bails him out. Prithvi and Maggie continue their courtship, but Stella finds out and intervenes, sending goons to attack Prithvi, during which Maggie is injured. How this affects everyone close to her is the crux of the story.
== Cast ==
Salman Khan as Prithvi Pandith
Revathi as Maggie Pinto
Amjad Khan aa Guruji
Babloo Mukherjee as Prithvi's Friend
Shafi Inamdar as John Pinto
Rita Bhaduri as Stella Pinto
Suhas Joshi as Prithvi's mother
Sudhir as Prithvi's Father
== Soundtrack ==
The songs are based on the original music composed by maestro Ilaiyaraaja for Telugu movie Prema. It was released on Venus Records & Tapes and composed by Anand–Milind and lyrics by Majrooh Sultanpuri.
== References ==
== External links ==
Love at IMDb | Love is a 1991 Indian Hindi-language romance film directed by Suresh Krissna, starring Salman Khan, Revathi (in her Bollywood debut) in the lead roles. It is the remake of the Telugu film Prema (1989). It could not repeat the success of the original and ended up as an average grosser. The makers changed the tragic climax from the original film to one with a happy ending. This movie is also remembered for the romantic song "Saathiya Tune Kya Kiya". The rights to this film are owned by Shah Rukh Khan's Red Chillies Entertainment. | 5 |
795 | love | Love (1991 Soviet film) (wikipedia) | Love (Russian: Любовь) is a 1991 Soviet romance film directed by Valery Todorovsky.
== Plot ==
A student meets a girl at a party. They understand each other and decide to get married. But the problem is that they are too different.
== Cast ==
Yevgeny Mironov as Sasha
Natalya Petrova as Mariya
Dmitry Maryanov as Vadim
Tatyana Skorokhodova as Marina
Natalya Vilkina
Inna Slobodskaya
Vija Artmane
Lev Durov
Anatoli Popolzukhin
Raisa Ryazanova
== References ==
== External links ==
Love at IMDb | Love (Russian: Любовь) is a 1991 Soviet romance film directed by Valery Todorovsky. | 0 |
796 | love | Love (2005 film) (wikipedia) | Love is a 2005 independent feature film, written, directed and edited by Vladan Nikolic, produced by Jim Stark (Down by Law, Night on Earth, Factotum) and executive produced by Christoph Thoke (Tropical Malady). The film was made in New York City for $350,000, with a cast and crew from over 20 countries, with 168 scenes, shot at over 60 locations. The film was shot on mini DV in 20 days, transferred to 35mm film, and received high praise in the September 2005 issue of American Cinematographer for its stylish look.
It impressed audiences and critics at the 2005 Tribeca Film Festival, Venice Film Festival, and the Oldenburg Film Festival. Love also won the Prix De Jeunes at the Cinéma Tout Ecran festival in Geneva, Switzerland. Critics compared the film to Pulp Fiction, Memento, Rashomon, and in its political subtext to Marathon Man and Dirty Pretty Things (Variety).
Told through a non-linear narrative from each of the characters' points of view, the film reconstructs the stories of a Yugoslav hit man (Sergej Trifunovic), his former lover (Geno Lechner), and her police officer boyfriend (Peter Gevisser), as their paths cross in New York.
== Plot ==
== Cast ==
Sergej Trifunovic as Vanya
Geno Lechner as Anna
Peter Gevisser as Dirk
Didier Flamand as Jean
Mario Padula as Manny
Al Nazemian as Ali (as Al Naz)
Liat Glick as Faye
Eric Frandsen as Hayes
Mariano Mederos as Rivera
== References ==
== External links ==
Love at IMDb
Love at AllMovie
Official website
Love at the 2nd edition of Venice Days (62nd Venice International Film Festival) | Love is a 2005 independent feature film, written, directed and edited by Vladan Nikolic, produced by Jim Stark (Down by Law, Night on Earth, Factotum) and executive produced by Christoph Thoke (Tropical Malady). The film was made in New York City for $350,000, with a cast and crew from over 20 countries, with 168 scenes, shot at over 60 locations. The film was shot on mini DV in 20 days, transferred to 35mm film, and received high praise in the September 2005 issue of American Cinematographer for its stylish look.
It impressed audiences and critics at the 2005 Tribeca Film Festival, Venice Film Festival, and the Oldenburg Film Festival. Love also won the Prix De Jeunes at the Cinéma Tout Ecran festival in Geneva, Switzerland. Critics compared the film to Pulp Fiction, Memento, Rashomon, and in its political subtext to Marathon Man and Dirty Pretty Things (Variety).
Told through a non-linear narrative from each of the characters' points of view, the film reconstructs the stories of a Yugoslav hit man (Sergej Trifunovic), his former lover (Geno Lechner), and her police officer boyfriend (Peter Gevisser), as their paths cross in New York. | 6 |
797 | love | Love (2008 Bengali film) (wikipedia) | Love is a 2008 Bengali film by Indian director Riingo Banerjee, and based upon Love Story by Erich Segal.
== Plot ==
The film is about two young people in love, who battle the odds, live through the tough times with a smile and who take a vow to never part until death. Jisshu plays Rahul Ray, a rich Hindu boy and management student, who falls in love with Ria Fernandez, a poor Christian music student, played by Koel Mallick.
== Cast ==
Jisshu Sengupta as Rahul Ray
Koel Mallick as Ria Fernandez
Krishnokishore Mukherjee
Chaitali Dasgupta
George Baker
== Soundtrack ==
== References ==
== External links ==
ilovekolkata.in review of film
Calcutta Tube - Online Bengali Movies
The Telegraph reviews
calonline.com
Telegraphindia.com: Story 1
Telegraphindia.com: Story 2
gomlo.in interview with director Riingo
Telegraphindia.com Story 3
Telegraphindia Story 4
Shoma A. Chatterji Screenindia.com "LOVE: A social vacuum (sic)" | Love is a 2008 Bengali film by Indian director Riingo Banerjee, and based upon Love Story by Erich Segal. | 0 |
798 | love | Love (2008 video game) (wikipedia) | Love (stylized as LOVE) is a platform game developed and published by American indie developer Fred Wood. It was originally released in May 2008, exclusively to the game's website, but was later released as an enhanced version entitled Love+ on February 7, 2014 to Early Access, with its final release being on February 14, 2014. For the game's fifth anniversary, it was released on Nintendo Switch on February 14, 2019.
The game's art style is minimalistic; every level in the game has only three colors: black, white, and a custom third that varies each level, where white serves to indicate interactive objects, black serves as the background, and the third color makes the platforms. The game also carries a pixel art style.
On November 7, 2017, a sequel titled LOVE 2: kuso was released, which includes all sixteen main levels from Love+. A third entry in the series, LOVE 3, was released on December 7, 2021 and includes all levels from the previous games.
== Gameplay ==
Love is a 2D platformer. The player character (known as fiveEight, as revealed in kuso) runs through several linear levels. They possess three abilities: jumping, moving left and right, and leaving a checkpoint behind at the push of a button. The player has 100 lives to play through 20 levels, in which the goal is to reach the end point in each to progress to the next.
Love+ nearly completely revamped the original game. It added three new game modes: "Easy Mode", which gives the player unlimited lives, "YOLO Mode", in which the player has only one life, and "Speedrun Mode", in which the goal is to finish the game in the shortest possible time. The original mode was renamed to "Arcade Mode". Many of the levels in the original game were scrapped, being replaced by completely new levels, and those that were carried over were heavily altered. Overall, Love+ has fewer levels in its main campaign than Love, with Love having twenty and Love+ having sixteen.
In updates, five more levels were added to Love+'s original line-up of eleven. Additionally, a fifth game mode titled "Remix Mode" was added in an update, which has the player play through seven "remixes" of levels from the main game, and later, in another update, a "bonus level" based on World 1-1 from Super Mario Bros. was added.
== Plot ==
fiveEight wakes up in a strange mechanical world, where everything they once knew has been replaced by machinery. They have no memory of what happened, except that things were much better before they woke up. They have nothing pushing them forward except a feeling in the back of their mind, telling them that there is a light at the end of the tunnel, with nothing but the hope of getting to something better.
== Development ==
Love was initially released to the website trunks.fireball20xl.com, first for a price of $1, but then for free. The game was later remade as Love+ and released to Steam under the title of LOVE. When creating custom levels, the game engine uses the bottom left pixel as the background color.
=== Music ===
The game's soundtrack was composed by James Bennett. The soundtrack has been described as "brilliant", and Bennett's compositional style has been said to be akin to "a 45-year old ice cream van making its way to the moon."
== Reception ==
Anthony Burch of Destructoid called the original game "charming", saying it was "straight platforming at its most inspired and difficult". Tim W. of Indiegames.com recommended the game for fans of "frustrating platformers".
Jonathan Kaharl of Hardcore Gaming 101 said that Love+ "demonstrates there is perfection to be found within simplicity". Tom Sykes praised it as being "all the retro platforming you need".
== References ==
== External links ==
Official website (archive) | Love (stylized as LOVE) is a platform game developed and published by American indie developer Fred Wood. It was originally released in May 2008, exclusively to the game's website, but was later released as an enhanced version entitled Love+ on February 7, 2014 to Early Access, with its final release being on February 14, 2014. For the game's fifth anniversary, it was released on Nintendo Switch on February 14, 2019.
The game's art style is minimalistic; every level in the game has only three colors: black, white, and a custom third that varies each level, where white serves to indicate interactive objects, black serves as the background, and the third color makes the platforms. The game also carries a pixel art style.
On November 7, 2017, a sequel titled LOVE 2: kuso was released, which includes all sixteen main levels from Love+. A third entry in the series, LOVE 3, was released on December 7, 2021 and includes all levels from the previous games.
| 6 |
799 | love | Love (2011 film) (wikipedia) | Love is a 2011 American science fiction drama film produced and scored by the alternative rock band Angels & Airwaves. The film is the directorial debut of filmmaker William Eubank. The film's world premiere took place on February 2, 2011, at the 26th Annual Santa Barbara International Film Festival and the film was later featured in the Seattle International Film Festival, FanTasia 2011, and a number of other festivals. The film was screened in 460 theatres across the United States on August 10, 2011, in the Love Live event.
Love portrays the personal-psychological effects of isolation and loneliness when an astronaut becomes stranded in space and through this, emphasizes the importance of human connection and love. Additionally, it touches on the fragility of humanity's existence (explored through a dying Earth-apocalyptic doomsday scenario) inspired by the cautions of Carl Sagan in Pale Blue Dot and considers the importance of memories and stories as humanity's legacy.
== Plot ==
During an 1864 battle of the American Civil War, a lone Union soldier, Captain Lee Briggs (Bradley Horne), is dispatched on a mission to investigate a mysterious object reported to Union forces. He leaves to venture on the mission.
Fast forward to 2039, United States Astronaut Lee Miller (Gunner Wright) is dispatched to the International Space Station (ISS) as a one-man skeleton crew to determine its safety and make any required adjustments, after it had been left unattended for two decades due to unspecified reasons. Shortly after his arrival, significant disturbances transpire on Earth, eventually leading Miller to lose contact with CAPCOM and finding himself stranded in orbit alone, forced to helplessly watch events on Earth from portholes 200 miles above his home planet. Miller struggles to maintain his sanity while in isolation by interacting with Polaroid pictures of former ISS crew members left aboard the ship.
Experiencing power issues, Miller moves into an unpressurised module of the space station to perform repairs and discovers the 1864 journal of Briggs. Miller reads Briggs's account of the war and becomes enthralled by the mysterious object he is searching for, not realizing he will soon become more familiar with the very same object, and not by accident.
By 2045, after six years without CAPCOM contact and a deteriorating oxygen system in the ISS, Miller puts on a space suit and goes for a spacewalk, deciding that it would be easier for him to detach his tether and slowly drift towards Earth and to burn in the atmosphere than slowly suffocate to death on board the ISS. He finds, however, that he is unable to go through with his suicide.
Miller is seen still aboard the ISS, presumably much later: his hair has grown extremely long, and he is extensively tattooed. He has drawn sketches of people and battles of the Civil War from the journal all over the interior of the ISS. The cramped quarters of the space station have become a rat's nest symbolic of his diminished sanity. He then seems to be contacted from outside the ISS, and to receive instructions to dock and transfer over. He does so, and seems to arrive in a giant uninhabited structure of distinctly human making. It is unclear whether this is real or imagined by Miller, who is now insane.
Miller wanders around until he happens upon a server mainframe where he finds a book titled A Love Story' As Told by 'You. Inside this book, he finds pictures of Captain Lee Briggs with his discovery, a gigantic cube-like alien object that may have helped advance Human society. In the index of the book, Miller finds a reference to himself and types it into the computer prompt. He then finds himself inside a generic hotel room, where a disembodied voice says:
How are you doing, Lee? Sorry about this projection, but it's the only way we could reach you. We can't tell you how relieved we are to have you here. Now, before we get ahead of ourselves, we have to tell you something. You're the last one, it's all gone. We understand how you might feel. Connection is perhaps the most cherished thing any being can have. That's the thing. That's why we've been listening. The place you see here is a scrapbook of sorts, a collection of memories and mementos of mankind's brief existence. It's a good thing we found you. We look forward to meeting you, Lee.
During the speech, we see the same cube-like object in space in the year 2045. The viewer is left to assume that this object has 'obtained' Lee Miller and is speaking directly to him. The film ends with the voice of a computer speaking of human connections and love.
== Production ==
The space station set was built in William Eubank's parents' backyard. In a making-of video uploaded to his Vimeo account, Eubank details the construction of the set and lists materials such as packing quilts, MDF, pizza bags, Velcro, insulation, Christmas lights, and other salvaged material as components to the ISS set. According to Tom DeLonge, the production was going to rent the space station from another movie but instead opted to construct it from salvaged materials for budget reasons.
Early teasers were released in 2007 and 2009. On January 10, 2011, the film's final trailer was released on Apple Trailers. The release of this trailer saw coverage on several industry websites.
== Release ==
=== Festival circuit ===
The film's world premiere took place on February 2, 2011, at the 26th Annual Santa Barbara International Film Festival, with additional screenings on February 3, 4 and 5 at the Metro 4 and Arlington Theater. The film was screened for free on February 11 at the Riviera Theatre in Santa Barbara as one of eleven films chosen as "Best of the Fest".
The 2011 Seattle International Film Festival featured Love in both their Sci-Fi and Beyond Pathway and their New American Cinema program. The film played on May 21 at the Pacific Place Theatre and May 22 at the SIFF Cinema. The film played a third time, June 11, at the Egyptian Theatre.
Love was accepted into the 2011 Fantasia International Film Festival held in Montreal, Quebec. Its FanTasia screening on July 18 in Hall Theatre, as part of the festival's Camera Lucida Section, marked the film's international premiere. The film also screened in Athens, Lund, London, Nantes, South Korea, Spain, Israel, and elsewhere.
=== Limited release ===
Love was shown nationwide on August 10, 2011.
=== Home media ===
Angels & Airwaves released a box set containing Love, the soundtrack to the film, Love Part I, and the band's fourth studio album Love Part II on November 8, 2011.
== Reception ==
At the Santa Barbara International Film Festival, the film was originally slotted for three showings but two additional showings in the Arlington Theatre were added after some original showings sold out.
Dennis Harvey, for Variety, wrote "[The film's] spiritual abstruseness and the script's myriad other ambiguities might infuriate in a film less ingeniously designed on more tangible fronts. But Love delights with the detail of its primary set as well as in accomplished effects, consistently interesting yet subservient soundtrack textures (the sole original song is reserved for the closing-credit crawl) and a brisk editorial pace ..."
Dustin Hucks, for Ain't It Cool News, wrote "Love can at times get very broad with scenes, dialogue, and flow ... if you're keen on clarity and the linear, Love is going to leave you frustrated. For others, however, – the challenge of understanding what is what may lead to a desire for repeat viewings, which for me – is a lot of fun ... This is a film that's clearly not for everyone – but has a lot to offer the Inception and Moon crowds."
Hucks continued to say Love was one of the most visually exciting low-budget films he had seen in some time and concluded with an overall endorsement: "Love is well worth seeking out in theaters – but don't miss it on DVD if you don't get the opportunity to view it in theaters."
== See also ==
Apollo 13, a 1995 film dramatizing the Apollo 13 incident
Gravity, 2013 3D science-fiction space drama film
Moon, a 2009 British science fiction drama film
List of films featuring space stations
== References ==
== External links ==
Official website
Love on Facebook
Love at IMDb
Love at the iTunes Preview
UPC 811481012617 | Love is a 2011 American science fiction drama film produced and scored by the alternative rock band Angels & Airwaves. The film is the directorial debut of filmmaker William Eubank. The film's world premiere took place on February 2, 2011, at the 26th Annual Santa Barbara International Film Festival and the film was later featured in the Seattle International Film Festival, FanTasia 2011, and a number of other festivals. The film was screened in 460 theatres across the United States on August 10, 2011, in the Love Live event.
Love portrays the personal-psychological effects of isolation and loneliness when an astronaut becomes stranded in space and through this, emphasizes the importance of human connection and love. Additionally, it touches on the fragility of humanity's existence (explored through a dying Earth-apocalyptic doomsday scenario) inspired by the cautions of Carl Sagan in Pale Blue Dot and considers the importance of memories and stories as humanity's legacy. | 5 |
800 | love | Love (2016 play) (wikipedia) | Love (stylized as LOVE) is a 2016 British play written by Alexander Zeldin. It is about a group of families who have been placed in temporary accommodation in the run-up to Christmas.
== Production history ==
The play premiered in the Dorfman Theatre at the National Theatre, London running from 6 December 2016 to 10 January 2017, before transferring to The Studio at the Birmingham Repertory Theatre from 26 January to 11 February 2017. The production later transferred the Queen's Theatre, Hornchurch from 25 to 28 October 2018.
A BBC film adaptation was first broadcast on BBC 2 on 8 December 2018.
The play made its North American debut at the Park Avenue Armory running from February 25 until March 25, 2023.
== Plot ==
The story of two families living in a temporary British housing accommodation.
== Critical reception ==
The Guardian wrote "It is filled with observant compassion but at first I found myself craving more political anger."
The Daily Beast called Love "The most powerful piece of theater currently being staged in New York."
== References == | Love (stylized as LOVE) is a 2016 British play written by Alexander Zeldin. It is about a group of families who have been placed in temporary accommodation in the run-up to Christmas. | 1 |
801 | love | Love (Aaron Carter EP) (wikipedia) | Love (stylized as LØVË) is the third and final EP by American singer and songwriter Aaron Carter, released on February 10, 2017, by Sony Music. It is the first collection of songs released by Carter since 2002.
== Background ==
On April 1, 2016, Carter released "Fool's Gold" as the first single from the EP. When speaking of the EP, Carter told Billboard:"'The 'LøVë' album and 'Fool's Gold' era has been D.I.Y. hustle since day one. "Everything from the production, songwriting, mixing, photoshoots, music videos, packaging and distribution have been a collective involvement from a team I like to call 'Team Fool's Gold.'"
The second single, "Sooner or Later", was released in January 2017.
== Reception ==
The EP received positive reception by music critics, with Entertainment Weekly saying "Sooner or Later" was "no "Aaron’s Party" — it's better". El Broide wrote that [Carter] "decided to take a tropical house approach with the project incorporating strong pop influences – and it works."
== Track listing ==
All songs are written by Jon Asher, Melanie Fontana, Taylor Helgeson, Michel Schulz and Aaron Carter; while being produced by the latter two.
== Charts ==
== References == | Love (stylized as LØVË) is the third and final EP by American singer and songwriter Aaron Carter, released on February 10, 2017, by Sony Music. It is the first collection of songs released by Carter since 2002. | 1 |
802 | love | Love (Aaron Carter album) (wikipedia) | Love (stylized as LØVË) is the fifth studio album by American singer and songwriter Aaron Carter, released on February 16, 2018, by Sony Music, and the last to be released in his lifetime. At the time of the album’s release it was Carter's first studio album in over fifteen years, since 2002's Another Earthquake. The album was preceded by an EP of the same name, released in 2017.
== Background and release ==
More than thirteen years after the release of his last studio album, titled Another Earthquake!, and a substantial number of greatest hits compilations, Carter appeared in media outlets talking about his return to music. According to the singer, he spent ten years learning how to make an album from scratch during his time out of the music business.
Carter began to tease the first single of the album, titled "Fool's Gold" which he wrote and produced himself, in November 2015 via Twitter. On November 24, 2015, Billboard premiered a preview of the song. The song and its accompanying music video, co-directed by Carter and Jon Asher, were released on April 1, 2016. The single did not manage to appear on major worldwide charts. At that time the singer also announced that an EP entitled LØVË would be released. Carter told Billboard: "'The 'LøVë' album and 'Fool's Gold' era has been D.I.Y. hustle since day one. Everything from the production, songwriting, mixing, photoshoots, music videos, packaging and distribution have been a collective involvement from a team I like to call 'Team Fool's Gold.'"
In 2017, Carter would release a second single titled "Sooner or Later" which became certified gold in Italy, his first gold record since "Saturday Night", which was certified in the US after selling over 500,000 copies, in 2005. In December 2017, he released the third and last single "Don't Say Goodbye" and announced a promotional tour in the United States. The singer also performed at a concert in Manila, Philippines.
To celebrate Valentine's Day and promote the album's release, Carter released a newly recorded and remixed version of his top ten hit from 2000, "I Want Candy", on February 14, 2018.
== Critical reception ==
Neil Z. Yeung, from AllMusic, rated the album three and a half stars out of five, writing that Carter does "an admirable job grasping the contemporary pop trends of 2017 and 2018 while adjusting his lyrical content from that of teen party jams to reflective heartbreak anthems."
Chuck Campbell, from the daily newspaper Knoxville News Sentinel, gave the album two out of five stars and described it as a "nondescript exercise in modern formula – shallow pop/EDM songs about relationships. And even compared to other fare in this genre, "Love" falls flat". He chose "the catchy" songs "Sooner or Later" and "Dearly Departed" as its best moments.
== Track listing ==
All songs produced by Aaron Carter and Michael “Brandon" Murphy.
== References == | Love (stylized as LØVË) is the fifth studio album by American singer and songwriter Aaron Carter, released on February 16, 2018, by Sony Music, and the last to be released in his lifetime. At the time of the album’s release it was Carter's first studio album in over fifteen years, since 2002's Another Earthquake. The album was preceded by an EP of the same name, released in 2017. | 2 |
803 | love | Love (Ai Otsuka) (wikipedia) | Love (ラブ) (stylized as LOVE) is a fictional female bunny character and singer created by Japanese singer Ai Otsuka. Love was to star in an album originally titled I canChu♥ and a promotional music video from I canChu♥, but the release was changed to a single and titled "Love no Theme" before it was released on April 11, 2007. Otsuka released a second single under Love titled "White Choco" on November 21, 2007. On November 18, 2009, the debut mini-album of Love was released, titled Love It.
== Description ==
According to the official profile, Love is a female bunny weighing 22 kilograms with a height of 99 centimeters. Her speech consists of few words. She is often shy and lonely, but acts restless. Love lacks the ability to jump and has slow movement, and her hobbies include turning over, being idle, and playing tricks. Love also likes cheap candy such as milk wafers, and dislikes people without substance, dentists, and non-organic vegetables.
== Discography ==
=== Albums ===
=== Singles ===
== References ==
== External links ==
LOVE Official Website | Love (ラブ) (stylized as LOVE) is a fictional female bunny character and singer created by Japanese singer Ai Otsuka. Love was to star in an album originally titled I canChu♥ and a promotional music video from I canChu♥, but the release was changed to a single and titled "Love no Theme" before it was released on April 11, 2007. Otsuka released a second single under Love titled "White Choco" on November 21, 2007. On November 18, 2009, the debut mini-album of Love was released, titled Love It. | 3 |
804 | love | Love (Angels & Airwaves album) (wikipedia) | Love (later retitled Love, Pt. 1) is the third studio album by the alternative rock band Angels & Airwaves. It was released on February 12, 2010, on Fuel TV, and on February 14 on Modlife. The album was released free of charge due to "corporate underwriting". A "special edition" hard copy version of the album was scheduled for release on March 22, 2011, along with a second disc containing new music from the band. This was announced at a Q & A for the movie, which stated that it would be delayed to fall 2011.
== Production ==
On January 12, 2010, the band released a promotional video entitled "C:\Transmission_Love", which contained a short preview of "The Flight of Apollo".
== Release and special editions ==
In May 2009, it was announced that the album would be released on Christmas Day. However, on July 19, 2009, DeLonge announced on Modlife that instead it would be released on Valentine's Day. The album was released free of charge through Modlife on Valentine's Day 2010.
The first single from the album, "Hallucinations" was released free of charge on December 23, 2009. The music video for "Hallucinations" was released on Modlife on February 27, 2010.
Angels & Airwaves released the album an hour and a half early on their Modlife page at 4:30pm Pacific Time to their premium members and Fuel TV subsequently released it at 6pm Pacific Time on February 12. free of charge.
When the album was first released, a version of the song "Hallucinations" remixed by Mark Hoppus was given to fans who donated to the band. This remix is no longer available to download.
Angels & Airwaves partnered with many companies with the release of the album, in an attempt to reach as many people as possible. Fuel TV, Loserkids.com and ONE, and the Keep-A-Breast Foundation are just some of the organizations that have helped the band release the record through links featured on their websites and through emails sent to the subscribers of their mailing lists.
== Sound ==
The music of Love, DeLonge says, has a progressive rock kind of flavor. "It's like blending Radiohead and U2 together with these kind of Pink Floyd movements", he explains. "Things happen unpredictably and take you to these epic soundscapes. It is very much in the spirit of Angels & Airwaves, but it sounds way, way more thought-out and way more ambitious."
== Reception ==
Love has received generally positive reviews from music critics. AbsolutePunk gave Love a 77%, while other sites such as The Daily Campus awarded it an 8/10.
== Track listing ==
Notes
The track "Letters to God, Pt. 2" serves as a sequel to the song "Letters to God" from DeLonge's early 2000's side-project Box Car Racer.
== Charts ==
Love charted on the US Billboard 200 when released on iTunes in 2011.
== Personnel ==
Angels & Airwaves
Tom DeLonge – lead vocals, rhythm guitar, keyboards
David Kennedy – lead guitar, keyboards, synthesizers
Matt Wachter – bass guitar, synthesizers, backing vocals
Atom Willard – drums, percussion
== Film ==
A movie with the same title, Love, was also released. It "tells a story of human life and destiny but at the same time really makes usual moments of life extraordinary. It is a circular narrative in many ways, where it kind of sums up the human race in a time capsule". A 3-minute trailer was released on Friday, July 31, 2009, on the Angels & Airwaves website, featuring explosions, heavy artillery and Civil War soldiers. Part of the song "Letters to God, Part II" was usfeatured during the video. The movie appears to involve scenes aboard the International Space Station, keeping true to Tom's apparent interest in space as seen in many Angels & Airwaves music videos. The official movie trailer was released on Apple Trailers on Friday, October 30, 2009, and made available on Modlife. The film is not related to the 2008 film, Start the Machine, a documentary that followed the making of the first album.
On January 7, Tom DeLonge shared a bit of the plot of the movie on ModCam, saying that the astronaut goes through a wormhole and meets God. More was released on the plot of the movie when DeLonge was interviewed by ABC. He said, on January 22, that the movie "centers on an astronaut who is stranded in a space station as the Earth collapses".
In an interview with Entertainment Weekly, DeLonge was asked what the movie Love was about. He said, "It starts in the Civil War and you travel through time and space. There's a couple of different storylines. The main one is, a guy gets sent up to the International Space Station, and he gets abandoned up there. He doesn't know why. So throughout his years of being stuck up there, he sees the Earth starting to collapse below. He ends up basically becoming the last person alive. And then decades later, he wakes up one day and there's something outside of his spaceship, in low Earth orbit with him."
On the Apple website, a description of the movie Love reads as follows: "After losing contact with Earth, Astronaut Lee Miller (Gunner Wright) becomes stranded in orbit alone aboard the International Space Station. As time passes and life support systems dwindle, Lee battles to maintain his sanity — and simply stay alive. His world is a claustrophobic and lonely existence, until he makes a strange discovery aboard the ship. Driven by the powerful music of Angels & Airwaves, Love explores the fundamental human need for connection and the limitless power of hope... A high-impact visual adventure, that resonates a common truth, that everyone has a story to tell and something even greater to leave behind."
== References == | Love (later retitled Love, Pt. 1) is the third studio album by the alternative rock band Angels & Airwaves. It was released on February 12, 2010, on Fuel TV, and on February 14 on Modlife. The album was released free of charge due to "corporate underwriting". A "special edition" hard copy version of the album was scheduled for release on March 22, 2011, along with a second disc containing new music from the band. This was announced at a Q & A for the movie, which stated that it would be delayed to fall 2011. | 4 |