comparative vs fewer

comparative is a noun but fewer is not a noun.

Word	Noun	Adjective	Verb	Adverb
comparative	Yes	Yes	No	No
fewer	No	Yes	No	No

comparative (noun)	fewer (noun)
the comparative form of an adjective or adverb

comparative (adjective)	fewer (adjective)
estimated by comparison; not absolute or complete	(comparative of `few' used with count nouns) quantifier meaning a smaller number of
relating to or based on or involving comparison