isomer

n. chemical compound which has the same number and kind of atoms as another but differs in structural arrangement (Chemistry)

In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of chemical bonds between atoms, but in which the atoms are arranged differently (analogous to a chemical anagram). Many isomers share similar if not identical properties in most chemical contexts. This should not be confused with a nuclear isomer, which involves a nucleus at different states of excitement.
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Isomer /iso·mer/ any compound exhibiting, or capable of exhibiting, isomerism.isomer´ic i·so·mer n. 1. [more]Isomer - Community and Resources

Noun
1. a compound that exists in forms having different arrangements of atoms but the same molecular weight
(hypernym) compound, chemical compound

n. isomer, chemical compound which has the same number and kind of atoms as another but differs in structural arrangement (Chemistry)

adj. isomeric, of a chemical compound which has the same number and kind of atoms as another but differs in structural arrangement (Chemistry)