disbelief vs dubiousness

disbelief and dubiousness both are nouns.

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

As nouns, dubiousness is a hypernym of disbelief; that is, dubiousness is a word with a broader meaning than disbelief:

Other hypernyms of disbelief include doubt, doubtfulness, dubiety, incertitude, uncertainty.

disbelief (noun)	dubiousness (noun)
doubt about the truth of something	uncertainty about the truth or factuality or existence of something
a rejection of belief	the state of being unsure of something