syntax vs grammar

syntax and grammar both are nouns.

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

As nouns, grammar is a hypernym of syntax; that is, grammar is a word with a broader meaning than syntax:

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

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