substantival vs grammar

substantival is not a noun while grammar is a noun.

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

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

substantival (adjective)	grammar (adjective)
of or relating to or having the nature or function of a substantive (i.e. a noun or noun equivalent)