Definitions

1. adjective

Describing a substance that can exist in two or more different physical forms, such as diamond and graphite, which are allotropes of carbon.

“Graphite and diamond are allotropes of carbon.”

2. noun

A different form of a chemical element, such as diamond, graphite, and fullerenes, which are allotropes of carbon.

“Carbon has several allotropes, including diamond, graphite, and fullerenes.”