grammar vs syntax

grammar and syntax both are nouns.

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

As nouns, syntax is a hyponym of grammar; that is, syntax is a word with a more specific, narrower meaning than grammar:

grammar: the branch of linguistics that deals with syntax and morphology (and sometimes also deals with semantics)
syntax: studies of the rules for forming admissible sentences

Other hyponyms of grammar include descriptive grammar, prescriptive grammar, morphology.

grammar (noun)	syntax (noun)
the branch of linguistics that deals with syntax and morphology (and sometimes also deals with semantics)	studies of the rules for forming admissible sentences
	the grammatical arrangement of words in sentences
	a systematic orderly arrangement