farthest vs furthest

farthest and furthest both are adjectives.

Word	Noun	Adjective	Verb	Adverb
farthest	No	Yes	No	Yes
furthest	No	Yes	No	Yes

As adjectives, farthest and furthest are synonyms defined as:

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

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

As adverbs, farthest and furthest are synonyms defined as:

farthest and furthest: to the greatest distance in space or time (`farthest' is used more often than `furthest' in this physical sense)

As adverbs, farthest and furthest are synonyms defined as:

farthest and furthest: to the greatest degree or extent or most advanced stage (`furthest' is used more often than `farthest' in this abstract sense)

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

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