What does folie mean?
Folie is the French word for madness, borrowed into English where it now lives almost entirely within fixed phrases rather than standing on its own. Its best-known use is the psychiatric term 'folie à deux', describing a rare condition in which two closely associated people come to share the same delusion — typically one dominant individual transmitting a false belief to a receptive partner. A related expression, 'folie de grandeur', corresponds to delusions of grandeur, an inflated sense of one's own importance. Because these phrases are retained verbatim from French, they carry a distinctly learned, clinical flavour, and writers sometimes deploy them ironically to characterise collective enthusiasm or groupthink as a kind of shared insanity. Outside such phrases, English speakers reach for native words like madness, insanity, or lunacy instead. The word ultimately derives from Latin follis, originally a bellows, whose sense of 'windbag' evolved into notions of empty-headedness and folly, linking folie to English words such as 'fool' and 'folly'.
nounFolie is a French borrowing meaning madness or insanity. In English it survives chiefly in fixed psychiatric and literary phrases, most famously 'folie à deux', a shared delusion transmitted between two closely associated people.
- Madness or insanity, especially as expressed in fixed French phrases such as 'folie à deux' (a delusion shared by two people) and 'folie de grandeur' (delusions of grandeur).
"The psychiatrist diagnosed the sisters with folie à deux, each reinforcing the other's delusions."
"The case of folie à deux drew national attention when both twins claimed an identical, impossible past."
"Critics dismissed the scheme as pure folie de grandeur."
The plural follows French usage and is rare in English, appearing mostly in historical or literary references to institutional 'folies'.
"The essay catalogued the royal court's successive folies with dry amusement."
The phrase 'folie à deux' literally means 'madness of two' — psychiatry's official term for a delusion shared by exactly two people.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of folie
Folie comes directly from Old French 'folie', derived from 'fol' ('mad, foolish'), which itself traces back to the Latin adjective 'follis' — originally meaning a bellows or windbag, and by extension an empty-headed or erratic person. English has long drawn on this French family: 'fool' entered Middle English through Anglo-Norman, and 'folly' arrived in the thirteenth century from the same Old French root. Modern English keeps folie itself only in borrowed phrases such as 'folie à deux', coined in nineteenth-century French psychiatric literature.
How folie is actually used
Folie is rarely used as a free-standing English word; it functions almost exclusively inside established French phrases retained in psychiatric and literary writing. In speech and writing outside those phrases, English speakers would normally say 'madness' or 'insanity'. It retains its French pronunciation and carries a slightly learned, clinical, or ironic tone.
Easily confused with folie
'Folly' is the native English word for foolishness or a foolish act, while 'folie' is the French borrowing denoting outright madness, used almost entirely within phrases like 'folie à deux'.