physical form of a chemical element that has distinct properties, or the existence of such forms; for example, graphite and diamond are both allotropes of carbon

The physical differences between males and females of the same species, such as size, color, or shape

(linguistics) Two or more words in a single language that come from the same original source word but have different forms and meanings.

Terms with identical pronunciation and meaning but different written forms (e.g. [[唯一|唯一|wei2 yi1]] and [[惟一|惟一|wei2 yi1]])