mental rejection vs incertitude

mental rejection and incertitude both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental rejection	Yes	No	No	No
incertitude	Yes	No	No	No

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

Other hypernyms of mental rejection include doubt, doubtfulness, dubiety, dubiousness, uncertainty.

mental rejection (noun)	incertitude (noun)
doubt about the truth of something	the state of being unsure of something