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1. Chemistry Any of two or more substances that have the same molecular formula but differ in the way their atoms are connected to each other, in the spatial orientation of their atoms, or, in the case of large molecules such as DNA, in their molecular topology.
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.
[Greek īsomerēs, having equal share : īso-, iso- + meros, part, share; see (s)mer- in Indo-European roots.]
i′so·mer′ic (-mĕr′ĭk) adj.
1. (Elements & Compounds) chem a compound that exhibits isomerism with one or more other compounds
2. (General Physics) physics a nuclide that exhibits isomerism with one or more other nuclides
i•so•mer(ˈaɪ sə mər)
a chemical compound or nuclide that displays isomerism.
[1865–70; < Swedish (1830) < Greek isomerḗs equally divided =iso- iso- + -merēs, adj. derivative of méos part, division]
One of two or more compounds composed of the same chemical elements in the same proportions but having a different arrangement of the atoms. Isomers differ from one another in at least one physical or chemical property. Lactose and sucrose are isomers.