- Chem. any of two or more chemical compounds having the same constituent elements in the same proportion by weight but differing in physical or chemical properties because of differences in the structure of their molecules
- Physics any of two or more nuclei possessing the same number of neutrons and protons, but existing in different energy states, and thus having different radioactive properties
Origin of isomerfrom Classical Greek isomer?s, equally divided from isos, equal + meros, a part: see merit
- 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.
- 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.
Origin of isomerGreek īsomerēs having equal share īso- iso- meros part, share ; see (s)mer-2 in Indo-European roots.
- nuclear isomer
- optical isomer
iso- + -mer