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. Fear, Gale Encyclopedia of Psychology, 2nd ed. Gale Group, 2001. Fear, International Dictionary of Psychoanalysis, The Gale Group 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 Old English term f?r meaning "calamity, disaster". The Old English term f?r meant not the emotion engendered by a calamity or disaster but rather the event
Source:
http://en.wikipedia.org/wiki/Fear