possibly vs peradventure

possibly is not a noun while peradventure is a noun.

Word	Noun	Adjective	Verb	Adverb
possibly	No	No	No	Yes
peradventure	Yes	No	No	Yes

As adverbs, possibly and peradventure are synonyms defined as:

Other synonyms of possibly include maybe, mayhap, perchance, perhaps.

possibly (noun)	peradventure (noun)
	doubt or uncertainty as to whether something is the case

possibly (adverb)	peradventure (adverb)
by chance	by chance
to a degree possible of achievement or by possible means