unlikely vs likelihood

unlikely is not a noun while likelihood is a noun.

Word	Noun	Adjective	Verb	Adverb
unlikely	No	Yes	No	No
likelihood	Yes	No	No	No

unlikely (noun)	likelihood (noun)
	the probability of a specified outcome

unlikely (adjective)	likelihood (adjective)
has little chance of being the case or coming about
not likely to be true or to occur or to have occurred
having a probability too low to inspire belief