modifier vs open-class word

modifier and open-class word both are nouns.

Word	Noun	Adjective	Verb	Adverb
modifier	Yes	No	No	No
open-class word	Yes	No	No	No

As nouns, open-class word is a hypernym of modifier; that is, open-class word is a word with a broader meaning than modifier:

Other hypernyms of modifier include content word.

modifier (noun)	open-class word (noun)
a gene that modifies the effect produced by another gene	a word to which an independent meaning can be assigned
a content word that qualifies the meaning of a noun or verb
a person who changes something
a moderator who makes less extreme or uncompromising