grammar vs illative

grammar is a noun but illative is not a noun.

Word	Noun	Adjective	Verb	Adverb
grammar	Yes	No	No	No
illative	No	Yes	No	No

grammar (noun)	illative (noun)
the branch of linguistics that deals with syntax and morphology (and sometimes also deals with semantics)

grammar (adjective)	illative (adjective)
	relating to or having the nature of illation or inference
	expressing or preceding an inference
	resembling or dependent on or arrived at by inference