allotrope

noun

Etymology: Back-formation from allotropy, as allo- + -trope, from Ancient Greek ἄλλος (állos, “other”), and τρόπος (trópos, “way, manner”).

1. Any form of an element that has a distinctly different molecular structure to another form of the same element, with different physical properties and often different chemical properties.
2. An other form, a different shape of a lexical unit.
3. An alternative shape of a cognitive structure.