/ ˈaɪsəmə(r); NAmE / noun
1.
( chemistry ) one of two or more compounds which have the same atoms, but in different arrangements
2.
( physics ) one of two or more nuclei that have the same atomic number , but different energy states
► iso·mer·ic / ˌaɪsəˈmerɪk; NAmE / adjective
► iso·mer·ism / ˈaɪsəmərɪzəm; NAmE / noun [ U ]
••
WORD ORIGIN
mid 19th cent.: from Greek isomerēs sharing equally, from isos equal + meros a share.