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folie à deux

[fo-lee uh doo; French faw-lee a dœ]
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noun, plural fo·lies à deux [fo-leez uh doo; French faw-lee za dœ] /fɒˈliz ə ˈdu; French fɔ li za ˈdœ/. Psychiatry.
  1. the sharing of delusional ideas by two people who are closely associated.

Origin of folie à deux

Borrowed into English from French around 1890–95
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for folie a deux

folie à deux

noun
  1. psychiatry mental illness occurring simultaneously in two intimately related persons who share some of the elements of the illness, such as delusions

Word Origin

French: madness involving two (people)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

folie a deux in Medicine

folie á deux

(fô-lē′ ä dœ, fŏl′ē)
n.
  1. A condition in which symptoms of a mental disorder occur simultaneously in two individuals who share a close relationship or association.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.