(grammar) a category of words having the same grammatical properties

a class of words or phrases that can substitute for one another without loss of grammaticality

a nonterminal in the grammar defined in BNF under "Syntax

a set of words and/or phrases in a language which share a significant number of common characteristics

A grammatical class determined on the basis of the syntactic role it fills in the construction of sentences, used in the formal description of language. It is labelled by a category symbol, such as NP, VP, PrepP. See also Phrase-Structure Rule, Syntax.

A syntactic category is either a phrasal category, such as noun phrase or verb phrase, which can be decomposed into smaller syntactic categories, or a lexical category, such as noun or verb, which cannot be further decomposed.