ALLOTROPY
allotropy, allotropism
(noun) the phenomenon of an element existing in two or more physical forms
Source: WordNet® 3.1
Etymology
Noun
allotropy (plural allotropies)
(chemistry) A property, exhibited by some elements of existing in multiple forms with different atomic structures.
Source: Wiktionary
Al*lot"ro*pism, Al*lot"ro*py, n. Etym: [Gr. allotropie.] (Chem.)
Definition: The property of existing in two or more conditions which are
distinct in their physical or chemical relations.
Note: Thus, carbon occurs crystallized in octahedrons and other
related forms, in a state of extreme hardness, in the diamond; it
occurs in hexagonal forms, and of little hardness, in black lead; and
again occurs in a third form, with entire softness, in lampblack and
charcoal. In some cases, one of these is peculiarly an active state,
and the other a passive one. Thus, ozone is an active state of
oxygen, and is distinct from ordinary oxygen, which is the element in
its passive state.
Source: Webster’s Unabridged Dictionary 1913 Edition