: one of two or more persons or things of the same kind that differ in some way from one another: such as
b : one of two or more different spellings (such as labor and labour) or pronunciations (as of economics \ek-, ēk-\) of the same word
c : one of two or more words (such as geographic and geographical) or word elements (such as mon- and mono-) of essentially the same meaning differing only in the presence or absence of an affix