An intense irrational fear that often leads to avoidance of an object or situation. Phobias (or phobic disorders) are common (for example, fear of spiders, or arachnophobia; fear of heights, or acrophobia) and usually begin in childhood or adolescence. Psychiatric nomenclature refers to phobias of specific places, objects, or situations as specific phobias. About one in two individuals report that they are afraid of public speaking; in very severe cases, this is considered a form of social phobia. Social phobias also include other kinds of performance fears (such as playing a musical instrument in front of others; signing a check while observed) and social interactional fears (for example, talking to people in authority; asking someone out for a date; returning items to a store). Individuals who suffer from social phobia often fear a number of social situations.