uttermost vs farthermost

uttermost is a noun but farthermost is not a noun.

Word	Noun	Adjective	Verb	Adverb
uttermost	Yes	Yes	No	No
farthermost	No	Yes	No	No

As adjectives, uttermost and farthermost are synonyms defined as:

uttermost and farthermost: (comparatives of `far') most remote in space or time or order

Other synonyms of uttermost include farthest, furthermost, furthest, utmost.

uttermost (noun)	farthermost (noun)
the greatest possible degree

uttermost (adjective)	farthermost (adjective)
(comparatives of `far') most remote in space or time or order	(comparatives of `far') most remote in space or time or order
of the greatest possible degree or extent or intensity