sure thing vs uncertain

sure thing is a noun but uncertain is not a noun.

Word	Noun	Adjective	Verb	Adverb
sure thing	Yes	No	No	No
uncertain	No	Yes	No	No

sure thing (noun)	uncertain (noun)
something that is certain

sure thing (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