[ ahy-suh-mer ]

  1. Chemistry. a compound displaying isomerism with one or more other compounds.

  2. Also called nuclear isomer. Physics. a nuclide that exhibits isomerism with one or more other nuclides.

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Origin of isomer

First recorded in 1865–70; back formation from isomeric

Words Nearby isomer Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use isomer in a sentence

British Dictionary definitions for isomer


/ (ˈaɪsəmə) /

  1. chem a compound that exhibits isomerism with one or more other compounds

  2. physics a nuclide that exhibits isomerism with one or more other nuclides

Derived forms of isomer

  • isomeric (ˌaɪsəˈmɛrɪk), adjective

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

Scientific definitions for isomer


[ īsə-mər ]

  1. Chemistry Any of two or more substances that have the same molecular formula but differ in their connectivity or spatial arrangement of atoms, or in their topology in macromolecules.

  2. Physics Any of two or more nuclei with the same mass number and atomic number that have different radioactive properties and can exist in any of several energy states for a measurable period of time.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.