[taw-tom-uh-riz-uh m]
noun Chemistry.
  1. the ability of certain organic compounds to react in isomeric structures that differ from each other in the position of a hydrogen atom and a double bond.

Origin of tautomerism

First recorded in 1880–85; tauto- + (iso)merism
Related formstau·to·mer·ic [taw-tuh-mer-ik] /ˌtɔ təˈmɛr ɪk/, adjectivenon·tau·to·mer·ic, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for tautomerism


  1. the ability of certain chemical compounds to exist as a mixture of two interconvertible isomers in equilibriumSee also keto-enol tautomerism
Derived Formstautomeric (ˌtɔːtəˈmɛrɪk), adjective

Word Origin for tautomerism

C19: from tauto- + isomerism
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

tautomerism in Medicine


  1. Chemical isomerism in which the isomeric forms differ little, usually only in the position of a hydrogen atom, and are able to exist in equilibrium and react with each other.
Related formstau′to•meric (tô′tə-mĕrĭk) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.