form class

WordReference Random House Unabridged Dictionary of American English © 2025

form′ class′, 

Grammar a class of words or forms in a given language that have one or more grammatical features in common, as, in Latin, all masculine nouns in the nominative singular, all masculine singular nouns, all masculine nouns, or all nouns.

• 1920–25

Collins Concise English Dictionary © HarperCollins Publishers::

form class noun

1. another term for part of speech
2. a group of words distinguished by common inflections, such as the weak verbs of English