disbelief vs incredulity

disbelief and incredulity both are nouns.

Word	Noun	Adjective	Verb	Adverb
disbelief	Yes	No	No	No
incredulity	Yes	No	No	No

As nouns, disbelief and incredulity are synonyms defined as:

Other synonyms of disbelief include mental rejection, scepticism, skepticism.

disbelief (noun)	incredulity (noun)
doubt about the truth of something	doubt about the truth of something
a rejection of belief