Definition of isomer noun from the Oxford Advanced Learner's Dictionary



    BrE BrE//ˈaɪsəmə(r)//
    ; NAmE NAmE//ˈaɪsəmər//
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  1. 1(chemistry) one of two or more compounds which have the same atoms, but in different arrangements
  2. 2(physics) one of two or more nuclei that have the same atomic number, but different energy states
  3. Word Originmid 19th cent.: from Greek isomerēs ‘sharing equally’, from isos ‘equal’ + meros ‘a share’.
See the Oxford Advanced American Dictionary entry: isomer