sweetener vs sweeten

sweetener is a noun but sweeten is not a noun.

Word	Noun	Adjective	Verb	Adverb
sweetener	Yes	No	No	No
sweeten	No	No	Yes	No

sweetener (noun)	sweeten (noun)
anything that serves as an enticement
something added to foods to make them taste sweeter

sweetener (verb)	sweeten (verb)
	make sweeter, more pleasant, or more agreeable
	make sweeter in taste