FAS vs syndrome

FAS and syndrome both are nouns.

Word	Noun	Adjective	Verb	Adverb
FAS	Yes	No	No	No
syndrome	Yes	No	No	No

As nouns, syndrome is a hypernym of FAS; that is, syndrome is a word with a broader meaning than FAS:

FAS: a congenital medical condition in which body deformation occurs or facial development or mental ability is impaired because the mother drinks alcohol during pregnancy
syndrome: a pattern of symptoms indicative of some disease

FAS (noun)	syndrome (noun)
a congenital medical condition in which body deformation occurs or facial development or mental ability is impaired because the mother drinks alcohol during pregnancy	a complex of concurrent things
	a pattern of symptoms indicative of some disease