an extreme, irrational fear of a specific object or situation. A phobia is classified as a type of anxiety disorder, since anxiety is the chief symptom experienced by the sufferer. Phobias are thought to be learned emotional responses. It is generally held that phobias occur when fear produced by an original threatening situation is transferred to other similar situations, with the original fear often repressed or forgotten. An excessive, unreasoning fear of water, for example, may be based on a forgotten childhood experience of almost drowning. The person accordingly tries to avoid that situation in the future, a response that, while reducing anxiety in the short term, reinforces the person's association of the situation with the onset of anxiety.

Although psychiatrists classify phobias as a single type of anxiety disorder, hundreds of words have been coined to specify the nature of the fear by prefixing “phobia” with the Greek word for the object feared. Among the more common examples are acrophobia, fear of high places; claustrophobia, fear of closed places; nyctophobia, fear of the dark; ochlophobia, fear of crowds; xenophobia, fear of strangers; and zoophobia, fear of animals. Agoraphobia, the fear of being in open or public places, is a particularly crippling illness that may prevent its victims from even leaving home. School phobia may afflict schoolchildren who are overly attached to a parent. See also anxiety.