certainty vs uncertain

certainty is a noun but uncertain is not a noun.

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

certainty (noun)	uncertain (noun)
something that is certain
the state of being certain

certainty (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