or my·o·sis

noun, plural mi·o·ses [mahy-oh-seez] /maɪˈoʊ siz/. Medicine/Medical.
  1. excessive constriction of the pupil of the eye, as a result of drugs, disease, or the like.
Compare mydriasis.

Origin of miosis

1810–20; variant of myosis < Greek mý(ein) to shut (the eyes) + -ōsis -osis
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for miosis



noun plural -ses (-siːz)
  1. excessive contraction of the pupil of the eye, as in response to drugs
  2. a variant spelling of meiosis (def. 1)
Derived Formsmiotic or myotic (maɪˈɒtɪk), adjective, noun

Word Origin for miosis

C20: from Greek muein to shut the eyes + -osis
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 miosis

1819, from Greek myein "to shut (the eyes)" + -osis. Greek myein is perhaps originally "to close the lips," from PIE *meue- "to be silent" (see mute (adj.)). Related: Miotic.

Online Etymology Dictionary, © 2010 Douglas Harper

miosis in Medicine


n. pl. mi•o••ses (-sēz)
  1. The period of decline of a disease in which the intensity of the symptoms begins to diminish.
  2. Constriction of the pupil of the eye, resulting from a normal response to an increase in light or caused by certain drugs or pathological conditions.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.