as yet vs heretofore

as yet and heretofore both are adverbs.

Word	Noun	Adjective	Verb	Adverb
as yet	No	No	No	Yes
heretofore	No	No	No	Yes

As adverbs, as yet and heretofore are synonyms defined as:

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

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

as yet (adverb)	heretofore (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