unfaithful vs fidelity

unfaithful is not a noun while fidelity is a noun.

Word	Noun	Adjective	Verb	Adverb
unfaithful	No	Yes	No	No
fidelity	Yes	No	No	No

unfaithful (noun)	fidelity (noun)
	the quality of being faithful
	accuracy with which an electronic system reproduces the sound or image of its input signal

unfaithful (adjective)	fidelity (adjective)
not true to duty or obligation or promises
having sexual relations with someone other than your husband or wife, or your boyfriend or girlfriend
having the character of, or characteristic of, a traitor
not trustworthy