legion vs many

legion is a noun but many is not a noun.

Word	Noun	Adjective	Verb	Adverb
legion	Yes	Yes	No	No
many	No	Yes	No	No

legion (noun)	many (noun)
a vast multitude
a large military unit
association of ex-servicemen
archaic terms for army

legion (adjective)	many (adjective)
amounting to a large indefinite number	a quantifier that can be used with count nouns and is often preceded by `as' or `too' or `so' or `that'; amounting to a large but indefinite number; quantifier, plural pronoun; quantifier, plural