en·​an·​tio·​mer i-ˈnan-tē-ə-mər How to pronounce enantiomer (audio)
: either of a pair of chemical compounds whose molecular structures have a nonsuperimposable mirror-image relationship to each other compare diastereomer
enantiomeric adjective

Example Sentences

Recent Examples on the Web And then there’s the case of esketamine, which is the S-enantiomer of ketamine, a similar (in molecular structure) but more potent agent than ketamine. Joshua Cohen, Forbes, 5 July 2021 Ketamine is a combination of two enantiomers, or mirror image molecules. Megan Thielking, Scientific American, 6 Mar. 2019 Strangely enough, meth's enantiomer is the active ingredient in Vick's Vapor Inhaler. William Herkewitz, Popular Mechanics, 19 Aug. 2013

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'enantiomer.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


Greek enantios + English -mer

First Known Use

circa 1929, in the meaning defined above

Time Traveler
The first known use of enantiomer was circa 1929

Dictionary Entries Near enantiomer

Cite this Entry

“Enantiomer.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/enantiomer. Accessed 21 Mar. 2023.

Medical Definition


en·​an·​tio·​mer in-ˈant-ē-ə-mər How to pronounce enantiomer (audio)
: either of a pair of chemical compounds whose molecular structures have a mirror-image relationship to each other

called also optical antipode

enantiomeric adjective
enantiomerically adverb

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