allotropy

{ } n. [ Gr. &unr_; other + direction, way, &unr_; to turn: cf. F. allotropie. ] (Chem.) The property of existing in two or more conditions which are distinct in their physical or chemical relations. [ 1913 Webster ]

☞ 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. [ 1913 Webster ]