Emily Dickinson Lexicon

I-SO-MORPH'ISM, n. [Gr. ισος, like, and μορφη, form.]

1. The quality of assuming the same crystaline form though composed of different elements, or proximate principles, yet with the same number of equivalents.
2. The quality of a substance by which it is capable of replacing another in a compound, without an alteration of the previous crystaline form of the compound.