particle vs function word

particle and function word both are nouns.

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

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

particle: a function word that can be used in English to form phrasal verbs
function word: a word that is uninflected and serves a grammatical function but has little identifiable meaning

Other hypernyms of particle include closed-class word.

particle (noun)	function word (noun)
a function word that can be used in English to form phrasal verbs	a word that is uninflected and serves a grammatical function but has little identifiable meaning
a body having finite mass and internal structure but negligible dimensions
(nontechnical usage) a tiny piece of anything