disbelief vs incertitude

disbelief and incertitude both are nouns.

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

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

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

disbelief (noun)	incertitude (noun)
doubt about the truth of something	the state of being unsure of something
a rejection of belief