doubtfulness vs uncertainness

doubtfulness and uncertainness both are nouns.

Word	Noun	Adjective	Verb	Adverb
doubtfulness	Yes	No	No	No
uncertainness	Yes	No	No	No

As nouns, uncertainness is a hypernym of doubtfulness; that is, uncertainness is a word with a broader meaning than doubtfulness:

doubtfulness: uncertainty about the truth or factuality or existence of something
uncertainness: being unsettled or in doubt or dependent on chance

Other hypernyms of doubtfulness include precariousness, uncertainty.

doubtfulness (noun)	uncertainness (noun)
uncertainty about the truth or factuality or existence of something	being unsettled or in doubt or dependent on chance
the state of being unsure of something