farthest vs comparative degree

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

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

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

farthest (adjective)	comparative degree (adjective)
(comparatives of `far') most remote in space or time or order

farthest (adverb)	comparative degree (adverb)
to the greatest distance in space or time (`farthest' is used more often than `furthest' in this physical sense)
to the greatest degree or extent or most advanced stage (`furthest' is used more often than `farthest' in this abstract sense)