# Glossary of civil engineering

This glossary of civil engineering terms is a list of definitions of terms and concepts pertaining specifically to civil engineering, its sub-disciplines, and related fields. For a more general overview of concepts within engineering as a whole, see Glossary of engineering.
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## A
### Abney level

    An instrument used in surveying which consists of a fixed sighting tube, a movable spirit level that is connected to a pointing arm, and a protractor scale. An internal mirror allows the user to see the bubble in the level while sighting a distant target. It can be used as a hand-held instrument or mounted on a Jacob's staff for more precise measurement.

### Abrams' law

    A law which states that the strength of a concrete mix is inversely related to the mass ratio of water to cement. As the water content increases, the strength of the concrete decreases.

### abrasion

    The process of scuffing, scratching, wearing down, marring, or rubbing away a substance or substrate. It can be intentionally imposed in a controlled process using an abrasive. Abrasion may also be an undesirable effect of exposure to normal use or exposure to the elements.

### absolute electrode potential

    In electrochemistry, according to an IUPAC definition, is the electrode potential of a metal measured with respect to a universal reference system (without any additional metal–solution interface).

### absolute pressure

    The pressure of a system that is zero-referenced against a perfect vacuum, using an absolute scale, so that it is equal to gauge pressure plus atmospheric pressure.

### absolute zero

    The theoretical lower limit of the thermodynamic temperature scale, at which the enthalpy and entropy of a cooled ideal gas reach their minimum values, taken as 0. Absolute zero is the point at which the fundamental particles of nature have minimal vibrational motion, retaining only quantum mechanical, zero-point energy-induced particle motion. The theoretical temperature is determined by extrapolating the ideal gas law; by international agreement, absolute zero is taken as −273.15° on the Celsius scale (International System of Units), which equals −459.67° on the Fahrenheit scale (United States customary units or Imperial units). The corresponding Kelvin and Rankine temperature scales set their zero points at absolute zero by definition.

### absorbance

    In chemistry, the common logarithm of the ratio of incident to transmitted radiant power through a material. Spectral absorbance or spectral decadic absorbance is the common logarithm of the ratio of incident to transmitted spectral radiant power through a material. Absorbance is a dimensionless quantity, and in particular is not a length, though it is a monotonically increasing function of path length, and approaches zero as the path length approaches zero.

### abutment

    The substructure at either end of a bridge span or dam whereon the structure's superstructure rests or contacts.

### AC power

    A type of electric power in alternating current circuits, wherein energy storage elements such as inductors and capacitors may result in periodic reversals of the direction of energy flow. Contrast DC power.

### acceleration

    In physics, the rate of change of velocity of an object with respect to time. An object's acceleration is the net result of any and all forces acting on the object, as described by Newton's Second Law. The SI unit for acceleration is metre per second squared (m s$^{−2}$). Accelerations are vector quantities (they have magnitude and direction) and add according to the parallelogram law. As a vector, the calculated net force is equal to the product of the object's mass (a scalar quantity) and its acceleration.

### acid

    A molecule or ion capable of donating a hydron (proton or hydrogen ion H$^+$), or, alternatively, capable of forming a covalent bond with an electron pair (a Lewis acid).

### acid-base reaction

    A chemical reaction that occurs between an acid and a base, which can be used to determine pH. Several theoretical frameworks provide alternative conceptions of the reaction mechanisms and their application in solving related problems; these are called the acid–base theories, for example, Brønsted–Lowry acid–base theory.

### acid strength

    The tendency of an acid, symbolised by the chemical formula HA, to dissociate into a proton, H$^+$, and an anion, A$^−$.

### acoustic board

    A special kind of board made of sound-absorbing materials, designed to provide sound insulation. Between two outer walls sound-absorbing material is inserted and the wall is porous. Thus, when sound passes through an acoustic board, the intensity of the sound is decreased. The loss of sound energy is typically balanced by the production of heat energy.

### acoustics

    The branch of physics that deals with the study of all mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound.

### activated sludge

    A type of wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa.

### activated sludge model

    A generic name for a group of mathematical methods to model activated sludge systems. The research in this area is coordinated by a task group of the International Water Association (IWA). Activated sludge models are used in scientific research to study biological processes in hypothetical systems. They can also be applied on full scale wastewater treatment plants for optimisation, when carefully calibrated with reference data for sludge production and nutrients in the effluent.

### active transport

    In cellular biology, the movement of molecules across a membrane from a region of their lower concentration to a region of their higher concentration—against the concentration gradient. Active transport requires cellular energy to achieve this movement. There are two types of active transport: primary active transport that uses ATP, and secondary active transport that uses an electrochemical gradient.

### actuator

    A mechanism by which a control system acts upon an environment. The control system can be simple (a fixed mechanical or electronic system), software-based (e.g. a printer driver, robot control system), a human, or any other input.

### acute angle

    An angle that is smaller than a right angle, i.e. less than 90 degrees. See also obtuse angle.

### adhesion

    The tendency of dissimilar particles or surfaces to cling to one another (cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can be divided into several types. The intermolecular forces responsible for the function of various kinds of stickers and sticky tape fall into the categories of chemical adhesion, dispersive adhesion, and diffusive adhesion. In addition to the cumulative magnitudes of these intermolecular forces, there are also certain emergent mechanical effects.

### adiabatic process

    In thermodynamics, an adiabatic process is one that occurs without transfer of heat or mass of substances between a thermodynamic system and its surroundings. In an adiabatic process, energy is transferred to the surroundings only as work. The adiabatic process provides a rigorous conceptual basis for the theory used to expound the first law of thermodynamics, and as such it is a key concept in thermodynamics.

### aerobic digestion

    A process in sewage treatment designed to reduce the volume of sewage sludge and make it suitable for subsequent use. More recently, technology has been developed that allows the treatment and reduction of other organic waste, such as food, cardboard and horticultural waste.

### aerodynamics

    The study of the motion of air, particularly its interactions with solid objects such as airplane wings. Aerodynamics is a sub-field of fluid dynamics and gas dynamics, and many aspects of aerodynamics theory are common to these fields.

### afocal system

    In optics, an optical system without focus, i.e. one that produces no net convergence or divergence of a beam of light, and which therefore has an infinite effective focal length.

### agricultural engineering

    The engineering discipline that studies agricultural production and processing. Agricultural engineering combines the disciplines of mechanical, civil, electrical and chemical engineering principles with a knowledge of agricultural principles according to technological principles. A key goal of this discipline is to improve the efficacy and sustainability of agricultural practices.

### albedo

    A measure of the diffuse reflection of solar radiation out of the total solar radiation received by an astronomical body (e.g. a planet like Earth). It is dimensionless and measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects all incident radiation).

### algebra

    A broad area of mathematics, together with number theory, geometry and analysis. In its most general form, algebra is the study of mathematical symbols and the rules for manipulating these symbols; it is a unifying thread of almost all of mathematics. It includes everything from elementary equation solving to the study of abstractions such as groups, rings, and fields. The more basic parts of algebra are called elementary algebra; the more abstract parts are called abstract algebra or modern algebra. Elementary algebra is generally considered to be essential for any study of mathematics, science, or engineering, as well as such applications as medicine and economics. Abstract algebra is a major area in advanced mathematics, studied primarily by professional mathematicians.

### algorithm

    An unambiguous specification of how to solve a class of problems. Algorithms can perform calculation, data processing and automated reasoning tasks.

### alkane

    In organic chemistry, an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carbon–carbon bonds are single. Alkanes have the general chemical formula C$_n$H$_{2n+2}$.

### alkene

    In organic chemistry, an unsaturated hydrocarbon that contains at least one carbon–carbon double bond.

### alkyne

    In organic chemistry, an unsaturated hydrocarbon containing at least one carbon—carbon triple bond.

### alloy

    A combination of metals or of a metal and another element. Alloys are defined by a metallic bonding character.

### alternating current (AC)

    A type of electric current which periodically reverses direction, in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. A common source of DC power is a battery cell in a flashlight. The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.

### ammeter

    A measuring instrument used to measure the current in a circuit.

### amino acid

    A class of organic compound containing amine (-NH$_2$) and carboxyl (-COOH) functional groups, along with a side chain (R group) specific to each amino acid. The key elements of an amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), although other elements are found in the side chains of certain amino acids.

### amorphous solid

    In condensed matter physics and materials science, a solid that lacks the long-range order that is characteristic of a crystal.

### ampere

    often shortened to "amp", is the base unit of electric current in the International System of Units (SI). It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics.

### amphoterism

    In chemistry, an amphoteric compound is a molecule or ion that can react both as an acid and as a base. Many metals (such as copper, zinc, tin, lead, aluminium, and beryllium) form amphoteric oxides or hydroxides. Amphoterism depends on the oxidation states of the oxide. Al$_2$O$_3$ is an example of an amphoteric oxide.

### amplifier

    An electronic device that can increase the power of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is a circuit that has a power gain greater than one.

### angular acceleration

    The rate of change of angular velocity. In three dimensions, it is a pseudovector. In SI units, it is measured in radians per second squared (rad/s$^2$), and is usually denoted by the Greek letter alpha (α).

### Anion

    is an ion with more electrons than protons, giving it a net negative charge (since electrons are negatively charged and protons are positively charged).

### Archimedes' principle

    states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces and acts in the upward direction at the center of mass of the displaced fluid. Archimedes' principle is a law of physics fundamental to fluid mechanics. It was formulated by Archimedes of Syracuse.

### architecture

    The process and the product of planning, designing, and constructing buildings or any other structures. Architectural works, in the material form of buildings, are often perceived as cultural symbols and as works of art. Historical civilizations are often identified with their surviving architectural achievements.

### architectural engineering

    The application of engineering principles and technology to building design and construction.

### automation

    The technology by which a process or procedure is performed with minimal human assistance. Automation or automatic control is the use of various control systems for operating equipment such as machinery, processes in factories, boilers and heat treating ovens, switching on telephone networks, steering and stabilization of ships, aircraft and other applications and vehicles with minimal or reduced human intervention.

### automaton

    Any self-operating machine, or a machine or control mechanism designed to automatically follow a predetermined sequence of operations, or respond to predetermined instructions.

### autonomous vehicle

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## B
### balance sheet

    In financial accounting, a summary of the financial balances of an individual or organization, whether it be a sole proprietorship, a business partnership, a corporation, private limited company or other organization such as a government or not-for-profit entity. Assets, liabilities and ownership equity are listed as of a specific date, such as the end of its financial year. A balance sheet is often described as a "snapshot of a company's financial condition". Of the four basic financial statements, the balance sheet is the only statement which applies to a single point in time of a business' calendar year.

### barometer

    A scientific instrument used to measure air pressure.

### battery

    A device consisting of one or more electrochemical cells with external connections provided to power electrical devices such as flashlights, mobile phones, and electric cars. When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal. When a battery is connected to an external electric load, a redox reaction converts high-energy reactants to lower-energy products, and the free-energy difference is delivered to the external circuit as electrical energy. Historically the term "battery" specifically referred to a device composed of multiple cells, however the usage has evolved to include devices composed of a single cell.

### beam

    A structural element that primarily resists loads applied laterally to its axis. Its mode of deflection is primarily by bending. The loads applied to the beam result in reaction forces at the beam's support points. The total effect of all the forces acting on the beam is to produce shear forces and bending moments within the beam, which in turn induce internal stresses, strains and deflections of the beam. Beams are characterized by their manner of support, profile (shape of cross-section), length, and material.

### bending moment

    The reaction induced in a structural element when an external force or moment is applied to the element causing the element to bend.

### Bernoulli's principle

    In fluid dynamics, Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.$^{:Ch.3}$$^{:156–164,§3.5}$ The principle is only applicable for isentropic flows: when the effects of irreversible processes (like turbulence) and non-adiabatic processes (e.g. heat radiation) are small and can be neglected.

### brittleness

    A physical property of a material such that, when subjected to stress, it breaks without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength.

### bulk modulus

    A measure of how resistant to compression a substance is, defined as the ratio of the infinitesimal pressure increase to the resulting relative decrease in volume. It is one of three standard moduli used to describe a material's response to stress, along with the shear modulus and Young's modulus.

### buoyancy

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## C
### calculus

    The mathematical study of continuous change.

### capacitance

    The ratio of the change in an electric charge in a system to the corresponding change in its electric potential.

### capillary action

    The ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.

### civil engineering

    The professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads, bridges, railways, canals, dams, airports, sewage systems, pipelines, structural components of buildings, and infrastructure for civic utilities.

### curvilinear motion

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## D
### Dalton's law

    In chemistry and physics, a law which states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. This empirical law was first observed by John Dalton in 1801 and published in 1802, and is closely related to the ideal gas laws.

### design engineer

    An engineer whose profession focuses on the engineering design process in any of the various disciplines of engineering, e.g. civil engineering. Design engineers tend to work on products and systems that involve adapting and using complex scientific and mathematical techniques in order to develop solutions for human society.

### dyne

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## E
### electrical network

    Any interconnection of electrical components (e.g. batteries, resistors, inductors, capacitors, switches, etc.), or a model of such an interconnection consisting of electrical elements (e.g. voltage sources, current sources, resistances, inductances, and capacitances).

### engineering physics

    The study of the combined disciplines of physics, mathematics and engineering, particularly computer, nuclear, electrical, electronic, materials or mechanical engineering. By focusing on the scientific method as a rigorous basis, it seeks ways to apply, design, and develop new solutions in engineering.

### exothermic

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## F
### flywheel

    A mechanical device which uses the conservation of angular momentum to store rotational energy. Flywheels are therefore a type of accumulator, analogous to electrical inductors, in that they store energy for later use. They are commonly used to smooth deviations in the power output of an energy source, to deliver stored energy at rates that exceed the ability of the energy source, and to control the orientation of mechanical systems.

### fusion

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## H
### half-life
### housewrap

    A synthetic material used to insulate and protect buildings. Housewrap functions as a weather-resistant barrier, preventing rain from getting into the wall assembly while allowing water vapor to pass to the exterior. If moisture from either direction is allowed to build up within stud or cavity walls, mold and rot can set in and fiberglass or cellulose insulation will lose its R-value due to heat-conducting moisture. House wrap may also serve as an air barrier if it is sealed carefully at seams.

### hydraulics
## I
### isotope

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## J
### joule (J)

    The derived unit of energy in the International System of Units. It is equal to the energy transferred to (or work done on) an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre (1 newton metre or N⋅m). It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889).

## M
### Mach number
### multidisciplinary design optimization

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## P
### parallel circuit
### pulley

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## S
### sanitary engineering
### surveying

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## T
### technical standard

    An established norm or requirement for a repeatable technical task, especially when written in a formal document that establishes uniform criteria, methods, processes, and practices. A technical standard may be developed privately or unilaterally by edict, or by groups such as trade associations, industry standards organizations, or governments, often according to the formal consensus of experts in the discipline.

### truss

    An assembly of two-force structural members such as beams, connected at nodes, where the members are organized such that the assemblage as a whole behaves as a single, rigid object.

### turbulence

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## U
### ultimate tensile strength (UTS)

    The maximum stress that a material under tension can withstand while being stretched or pulled before breaking. Ultimate tensile strength is usually found by performing a tensile test and recording the stress versus strain; the highest point of the stress–strain curve is the ultimate tensile strength. Tensile strengths are often important in the design of brittle members. Contrast compressive strength.

### utility frequency

    The nominal frequency of the oscillations of alternating current (AC) in a wide area synchronous grid transmitted from a power station to an end-user. In much of the world the utility frequency is standardized at 50 Hz, although in the Americas and parts of Asia it is typically 60 Hz.

## Z
### Zero Defects (ZD)

    A management-led program to eliminate defects in industrial production that enjoyed brief popularity in American industry from 1964 to the early 1970s. Quality expert Philip Crosby later incorporated it into his "Absolutes of Quality Management" and it enjoyed a renaissance in the American automobile industry—as a performance goal more than as a program—in the 1990s. Although applicable to any type of enterprise, it has been primarily adopted within supply chains wherever large volumes of components are being purchased (common items such as nuts and bolts are good examples).

### zeroth law of thermodynamics

    States that if two thermodynamic systems are each in thermal equilibrium with a third one, then they are in thermal equilibrium with each other. Accordingly, thermal equilibrium between systems is a transitive relation. Two systems are said to be in the relation of thermal equilibrium if they are linked by a wall permeable only to heat and they do not change over time. As a convenience of language, systems are sometimes also said to be in a relation of thermal equilibrium if they are not linked so as to be able to transfer heat to each other, but would still not do so (even) if they were connected by a wall permeable only to heat.
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