delusion
n. an often highly personal idea or belief system, not endorsed by one’s culture or subculture, that is maintained with conviction in spite of irrationality or evidence to the contrary. Delusions may be transient and fragmentary, as in delirium, or highly systematized and elaborate, as in delusional disorders, though most of them fall between these two extremes. Common types include delusional jealousy, delusions of being controlled, delusions of grandeur, delusions of persecution, delusions of reference, nihilistic delusions (see nihilism), and somatic delusions. Data suggest that delusions are not primarily logical errors but are derived from emotional material. They have come to represent one of the most important factors in systems for diagnostic classification. Some researchers believe that delusions may be the most important symptom of schizophrenia. See also
bizarre delusion; fragmentary delusion; systematized delusion.