furthest vs farthest

furthest and farthest both are adjectives.

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

As adjectives, furthest and farthest are synonyms defined as:

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

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

As adverbs, furthest and farthest are synonyms defined as:

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

As adverbs, furthest and farthest are synonyms defined as:

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

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

furthest (adverb)	farthest (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)