1. One of two or more substances displaying isomerism (q.v.); e.g., l-glucose and d-glucose or citrate and isocitrate. Cf.:stereoisomer. 2. One of two or more nuclides having the same atomic and mass numbers but differing in energy states for a finite period of time; e.g., 99mTc and 99Tc. [iso- + G. meros, part]
- geometric i. geometric isomerism.
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iso·mer 'ī-sə-mər n
1) any of two or more compounds, radicals, or ions that contain the same number of atoms of the same elements but differ in structural arrangement and properties
2) a nuclide isomeric with one or more others
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iso·mer (iґso-mər) [iso- + Gr. meros part] any compound exhibiting, or capable of exhibiting, isomerism. An isomer may be structural or stereochemical; see isomerism.Medical dictionary. 2011.