syntax vs sentence structure

syntax and sentence structure both are nouns.

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

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

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

Other synonyms of syntax include phrase structure.

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