earliest vs comparative degree

earliest is not a noun while comparative degree is a noun.

Word	Noun	Adjective	Verb	Adverb
earliest	No	Yes	No	Yes
comparative degree	Yes	No	No	No

earliest (noun)	comparative degree (noun)
	the comparative form of an adjective or adverb

earliest (adjective)	comparative degree (adjective)
(comparative and superlative of `early') more early than; most early

earliest (adverb)	comparative degree (adverb)
with the least delay