thus far vs as yet

thus far and as yet both are adverbs.

Word	Noun	Adjective	Verb	Adverb
thus far	No	No	No	Yes
as yet	No	No	No	Yes

As adverbs, thus far and as yet are synonyms defined as:

thus far and as yet: used in negative statement to describe a situation that has existed up to this point or up to the present time

Other synonyms of thus far include heretofore, hitherto, so far, til now, until now, up to now, yet.

thus far (adverb)	as yet (adverb)
used in negative statement to describe a situation that has existed up to this point or up to the present time	used in negative statement to describe a situation that has existed up to this point or up to the present time