numeral vs open-class word

numeral and open-class word both are nouns.

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

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

Other hypernyms of numeral include content word.

numeral (noun)	open-class word (noun)
a symbol used to represent a number	a word to which an independent meaning can be assigned
a word expressing a number.

numeral (adjective)	open-class word (adjective)
of or relating to or denoting numbers