unnecessary vs excess

unnecessary is not a noun while excess is a noun.

Word	Noun	Adjective	Verb	Adverb
unnecessary	No	Yes	No	No
excess	Yes	Yes	No	No

unnecessary (noun)	excess (noun)
	excessive indulgence
	immoderation as a consequence of going beyond sufficient or permitted limits
	a quantity much larger than is needed
	the state of being more than full

unnecessary (adjective)	excess (adjective)
not necessary	more than is needed, desired, or required