sentence structure vs syntax

sentence structure and syntax both are nouns.

Word	Noun	Adjective	Verb	Adverb
sentence structure	Yes	No	No	No
syntax	Yes	No	No	No

As nouns, sentence structure and syntax are synonyms defined as:

sentence structure and syntax: the grammatical arrangement of words in sentences

Other synonyms of sentence structure include phrase structure.

sentence structure (noun)	syntax (noun)
the grammatical arrangement of words in sentences	studies of the rules for forming admissible sentences
	the grammatical arrangement of words in sentences
	a systematic orderly arrangement