restricted vs grammar

restricted is not a noun while grammar is a noun.

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

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

restricted (adjective)	grammar (adjective)
subject to restriction or subjected to restriction
the lowest level of official classification for documents
restricted in meaning; (as e.g. `man' in `a tall man')