Fear
Fear is an emotional response to tangible and realistic dangers. Fear should be distinguished from anxiety, an emotion that often arises out of proportion to the actual threat or danger involved, and can be subjectively experienced without any specific attention to the threatening object. 
Most fear is usually connected to pain (i.e., some fear heights because if they fall, when they land, they will be in great pain). Behavioral theorists, like Watson and Ekman, have both suggested that fear is one of several very basic emotions (e.g., joy and anger). Fear is a survival mechanism, and usually occurs in response to a specific negative stimulus.

# Etymology
The English term "fear" originally comes from the Latin term Feanis meaning "calamity, disaster". The Old English term fr meant not the emotion engendered by a calamity or disaster but rather the event itself. The first recorded usage of the term "fear" with the sense of the emotion of fear is found in a medieval work written in Middle English and composed around 1290. The most probable explanation for the change in the meaning of the word fear is the existence in Old English of the related verb fran, which meant to terrify, take by surprise. 

# Varieties
Serious fear is a response to some formidable impending peril, while trifling fear arises from confrontation with inconsequential danger.
Fear can be described by different terms in accordance with its relative degrees. Personal fear varies extremely in degree from mild caution to extreme phobia and paranoia. Fear is related to a number of emotional states including worry, anxiety, terror, fright, paranoia, horror, panic (social and personal), persecution complex and dread.
Fears may be a factor within a larger social network, wherein personal fears are synergetically compounded as mass hysteria.
- Paranoia is a term used to describe a psychosis of fear, described as a heightened perception of being persecuted, false or otherwise. This degree of fear often indicates that one has changed their normal behavior in radical ways, and may have become extremely compulsive. Sometimes, the result of extreme paranoia is a phobia.
- Distrust in the context of interpersonal fear, is sometimes explained as the inward feeling of caution, usually focused towards a person, representing an unwillingness to trust in someone else. Distrust is not a lack of faith or belief in someone, but a feeling of warning towards someone or something questionable or unknown. For example, one may "distrust" a stranger who acts in a way that is perceived as "odd." Likewise one may "distrust" the safety of a rusty old bridge across a 100 ft drop.
- Terror refers to a pronounced state of fear - which usually occurs before the state of horror - when someone becomes overwhelmed with a sense of immediate danger. Also, it can be caused by perceiving the (possibly extreme) phobia. As a consequence, terror overwhelms the person to the point of making irrational choices and non-typical behavior.
Fear can also affect the subconscious and unconscious mind, most notably through nightmares.
Fear can also be imagined, and the sideffects can also be imagined.

# Causes
- Although fear is an innate response, objects of fear can be learned. This has been studied in psychology as fear conditioning, beginning with Watson's Little Albert experiment in 1920. In this study, an 11-month-old boy was conditioned to fear a white rat in the laboratory. In the real world, fear may also be acquired by a traumatic accident. For example, if a child falls into a well and struggles to get out, he or she may develop a fear of wells, enclosed spaces (claustrophobia) or of water (hydrophobia).
- Researchers have found that certain fears (e.g. animals, heights) are much more common than others (e.g. flowers, clouds). They are also much easier to induce in the laboratory. This phenomenon has been called preparedness. Physiologically, the fear response is linked to activity in the amygdala of the limbic system.
- The experience of fear may also be influenced by social norms and values. In the early 20th century, many people feared polio, a disease which cripples the body part it affects, leaving the body part immobilized for the rest of one's life.
- Drug side effect: Hydrocodone bitartrate and acetaminophen

# Characteristics

## Behavioral
In fear, one may go through various emotional stages. A good example of this is the cornered rat, which will try to run away until it is finally cornered by its predator, at which point it will become belligerent and fight back with heavy aggression until it either escapes or is destroyed.
The same goes for most animals. Humans can become very intimidated by fear; causing them to go along with another's wishes without caring about their own input. They can also become equally violent, and can even become deadly; it is an instinctive reaction caused by rising adrenaline levels rather than a consciously thought-out decision. This is why in many cases the full penalty cannot be made in cases of the court of law.
The facial expression of fear includes the following components:
- One's eyes widen (out of anticipation for what will happen next)
- The pupils dilate (to take in more light)
- The upper lip rises
- The brows draw together
- Lips stretch horizontally.

## Physiological
The physiological effects of fear can be better understood from the perspective of the sympathetic nervous responses (fight-or-flight), as compared to parasympathetic response, which is a more relaxed state.
- muscles used for physical movement are tightened and primed with oxygen in preparation for a physical fight or flight response.
- perspiration occurs due to blood being shunted from body's viscera to the peripheral parts of the body. Blood that is shunted from the viscera to the rest of the body will transfer, along with oxygen and nutrients, heat, prompting perspiration to cool the body.
- when the stimulus is shocking or abrupt, a common reaction is to cover or otherwise protect vulnerable parts of the anatomy, particularly the face and head.
- when a fear stimulus occurs unexpectedly, the victim of the fear response could possibly jump or give a small start.
- the person's heart rate and heartbeat may increase.
Fear is the flip side of anger in the inbuilt human 'fight or flight' response.
Many people feel the effects of fear on a day to day basis in the workplace through the stress of a modern working environment. This fear has a direct correlation to one's working efficiency and has been crystallised into a chart through an ongoing linear study in Bristol. The fear-o-meter shows the range of emotions caused by the latent fear that a significant workload and impending deadline can create. Whilst one's ability to work effectively diminishes as the level of fear increases, productivity on the other hand increases exponentially as the impending deadline approaches. For example, a student might fail to start an essay until the level of fear reaches 5 or above, choosing to either go out or perform menial tasks until the fear has increased to the required level.
- Satisfaction
- Ennui
- Despondency
- Anxiety
- Fear / Vexed
- Despair / Anger
- Apathy / Rage
- Terror / Apoplectic

# Moral and legal issues
Fear may be a consideration in determining the wrongness of acts, in some views. 
Actions done under stress of fear, unless of course it be so intense as to have dethroned reason, are accounted the legitimate progeny of the human will, or are, as the theologians say, simply voluntary, and therefore imputable. The reason is obvious; such acts lack neither adequate advertence nor sufficient consent, even though the latter be elicited only to avoid a greater evil or one conceived to be greater. Inasmuch, however, as they are accompanied by a more or less vehement repugnance, they are said to be in a limited and partial sense involuntary.
Since fear diminishes freedom of action, contracts entered into through fear may be judged invalid; similarly fear sometimes excuses from the application of the law in a particular case; it also excuses from the penalty attached to an act contrary to the law. The cause of fear is found in oneself or in a natural cause (intrinsic fear) or it is found in another person (extrinsic fear). Fear may be grave, such for instance as would influence a steadfast man, or it may be slight, such as would affect a person of weak will. In order that fear may be considered grave, certain conditions are requisite: the fear must be grave in itself, and not merely in the estimation of the person fearing; it must be based on a reasonable foundation; the threats must be possible of execution; the execution of the threats must be inevitable. Fear, again, is either just or unjust, according to the justness or otherwise of the reasons which lead to the use of fear as a compelling force. Reverential fear is that which may exist between superiors and their subjects. Grave fear diminishes willpower but cannot be said to totally take it away, except in some very exceptional cases. Slight fear (metus levis) is not considered even to diminish the will power, hence the legal expression "Foolish fear is not a just excuse."

# Death from fear
Research conducted at the University of California, San Diego and published in the British Medical Journal, suggests that deaths attributed to heart mortality increase under psychological stress, particularly terror. Otherwise healthy people have been known to be "scared to death," that is, to suddenly die under extreme fear or emotional trauma. People of all ages have died from fright brought on by everything from earthquakes to amusement-park rides.
While the mechanism is not fully understood, it is believed that sudden death can occur from cardiac arrhythmia brought on by a terrifying event. While the otherwise instinctual flight-or-fight response, which prepares the body for impending danger, is countered by the parasympathetic nervous system when the danger has passed, in certain cases an excessive response can damage the heart enough to kill.