multiplicity vs many

multiplicity is a noun but many is not a noun.

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

multiplicity (noun)	many (noun)
a large number
the property of being multiple

multiplicity (adjective)	many (adjective)
	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