uncertainness vs uncertainty

uncertainness and uncertainty both are nouns.

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

As nouns, uncertainness and uncertainty are synonyms defined as:

uncertainness and uncertainty: being unsettled or in doubt or dependent on chance

Other synonyms of uncertainness include precariousness.

uncertainness (noun)	uncertainty (noun)
being unsettled or in doubt or dependent on chance	being unsettled or in doubt or dependent on chance
	the state of being unsure of something