uncertainness vs uncertain

uncertainness is a noun but uncertain is not a noun.

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

uncertainness (noun)	uncertain (noun)
being unsettled or in doubt or dependent on chance

uncertainness (adjective)	uncertain (adjective)
	not established beyond doubt; still undecided or unknown
	lacking or indicating lack of confidence or assurance
	not certain to occur; not inevitable
	not established or confirmed
	ambiguous (especially in the negative)
	not consistent or dependable
	subject to change