Fear is the emotion of pain or uneasiness caused by the sense of impending danger, or by the prospect of some possible evil (OED Definition 1.2)
The original definition of fear in Old English was a sudden and terrible event or peril, used first in the year 453 AD. The first use of the English version of fear was in 1175.
The Old English Fǽr (and the Middle English variants fore and fár) corresponds to the Old Saxon fâr and means strong masculine, sudden calamity, or danger.
When asked about their fears some common responses from people are ghosts, cockroaches, spiders, snakes, heights, water, enclosed spaces, tunnels, bridges, needles, failure, public speaking, flying, clowns, intimacy, death, and rejection.
Fear can be conditioned, which was proved in John B. Watson's Little Albert experiment. Watson took a 9-month-old boy and exposed him to a variety of animals. Later, when Albert was playing with a white rat, Watson would make a loud noise to frighten Albert whenever he touched the rat. After that happening several times, Albert would show fear whenever the rat was in the room. Eventually, Albert was also scared of anything that resembled a white rat, including a rabbit, a fur coat, and cotton balls.
The physiological changes in the body associated with fear are summarized as the fight or flight response. It is a primitive mechanism that helps people and animals to survive by fighting or fleeing from danger. Without fear, species would die out due to predators. In animals, this is generally referred to as Island tameness or ecological naivete, where a species has lived in isolation for so long that they lose wariness for potential predators, leading to extinction, like the Dodo Bird.
What fear are you going to face today?