determiner vs function word

determiner and function word both are nouns.

Word	Noun	Adjective	Verb	Adverb
determiner	Yes	No	No	No
function word	Yes	No	No	No

As nouns, function word is a hypernym of determiner; that is, function word is a word with a broader meaning than determiner:

determiner: one of a limited class of noun modifiers that determine the referents of noun phrases
function word: a word that is uninflected and serves a grammatical function but has little identifiable meaning

Other hypernyms of determiner include closed-class word.

determiner (noun)	function word (noun)
a determining or causal element or factor	a word that is uninflected and serves a grammatical function but has little identifiable meaning
one of a limited class of noun modifiers that determine the referents of noun phrases
an argument that is conclusive