folie

Folie is a French noun meaning madness or insanity. In historical medical and psychiatric usage it referred to a broad range of severe mental disturbances. In modern clinical practice the term is considered imprecise and is rarely used as a diagnostic label; clinicians instead apply specific diagnoses such as psychotic disorders, mood disorders with psychotic features, or delusional disorders.

Etymology and usage: The word folIie derives from French and has long appeared in medical, literary, and philosophical contexts. In English, the cognate term folly entered through French and has carried diverse meanings, including foolish conduct or a frivolous building called a folly in architectural parlance. The contemporary psychological sense of folie is largely historical, with emphasis placed on discrete disorders rather than a single umbrella concept.

Notable concepts: One well-known phenomenon historically described under folie is folie à deux, or shared psychosis. This refers to a delusional belief system that develops within two or more people in a close relationship, usually initiated by a dominant individual and transmitted to others. Modern psychiatry treats such cases as manifestations of an underlying psychotic disorder in one person, with the second person affected secondarily; diagnosis and treatment focus on the primary condition, separation when feasible, and addressing psychosocial factors. The term is now less often used as a standalone diagnosis in favor of precise clinical classifications.

Cultural and historical context: Folie has influenced literature, philosophy, and art as a symbol of irrationality or crisis. In broader English usage, “folly” likewise denotes foolish conduct or, in architecture, a decorative, often whimsical outbuilding.