Fear is defined as an unpleasant emotion caused by the belief that someone or something is dangerous, That this unknown is likely to cause pain, or a threat.
Fear is a feeling induced by perceived danger or threat that occurs in certain types of organisms, which causes a change in metabolic and organ functions and ultimately a change in behavior, such as fleeing, hiding, or freezing from perceived traumatic events.
Synonyms of fear are: terror, fright, fearfulness, horror, alarm, panic, agitation, trepidation, dread, consternation, dismay, distress.