Insanity, madness, and craziness are terms that describe a spectrum of individual and group behaviors that are characterized by certain abnormal mental or behavioral patterns. Insanity can be manifest as violations of societal norms, including a person or persons becoming a danger to themselves or to other people. Conceptually, mental insanity also is associated with the biological phenomenon of contagion as in the case of copycat suicides. In contemporary usage, the term insanity is an informal, un-scientific term denoting "mental instability"; thus, the term insanity defense is the legal definition of mental instability. In medicine, the general term psychosis is used to include the presence either of delusions or of hallucinations or both in a patient; and psychiatric illness is "psychopathology", not mental insanity.
