[id-ee-uh-sing-kruh-see, -sin-]

noun, plural id·i·o·syn·cra·sies.

a characteristic, habit, mannerism, or the like, that is peculiar to an individual.
the physical constitution peculiar to an individual.
a peculiarity of the physical or the mental constitution, especially susceptibility toward drugs, food, etc.Compare allergy(def 1).

Also idiocrasy.

Origin of idiosyncrasy

1595–1605; < Greek idiosynkrāsía, equivalent to idio- idio- + syn- syn- + krâs(is) a blending + -ia -y3
Related formsid·i·o·syn·crat·ic [id-ee-oh-sin-krat-ik, -sing-] /ˌɪd i oʊ sɪnˈkræt ɪk, -sɪŋ-/, adjective

Synonyms for idiosyncrasy Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for idiosyncrasy

Historical Examples of idiosyncrasy

  • The Night (it must have been her idiosyncrasy) put her tongue out at them, too.

    The Arrow of Gold

    Joseph Conrad

  • He did not even try to investigate this idiosyncrasy of his chief.


    Joseph Conrad

  • This idiosyncrasy his companion, de Spain, had learned to tolerate.

    Nan of Music Mountain

    Frank H. Spearman

  • It was an idiosyncrasy of Jackson's to gather and take with him every filing.

    The Long Roll

    Mary Johnston

  • Long and often did Lorna puzzle over this idiosyncrasy of her father.

British Dictionary definitions for idiosyncrasy


noun plural -sies

a tendency, type of behaviour, mannerism, etc, of a specific person; quirk
the composite physical or psychological make-up of a specific person
an abnormal reaction of an individual to specific foods, drugs, or other agents

Word Origin for idiosyncrasy

C17: from Greek idiosunkrasia, from idio- + sunkrasis mixture, temperament, from sun- syn- + kerannunai to mingle
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

Word Origin and History for idiosyncrasy

c.1600, from French idiosyncrasie, from Greek idiosynkrasia "a peculiar temperament," from idios "one's own" (see idiom) + synkrasis "temperament, mixture of personal characteristics," from syn "together" (see syn-) + krasis "mixture" (see rare (adj.2)). Originally in English a medical term meaning "physical constitution of an individual." Mental sense first attested 1660s.

Online Etymology Dictionary, © 2010 Douglas Harper

idiosyncrasy in Medicine




A structural or behavioral trait peculiar to an individual or a group.
A physiological or temperamental peculiarity.
An unusual individual reaction to food or a drug.
Related formsid′i•o•syn•cratic (-sĭn-krătĭk) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.