sweeten vs sweetening

sweeten is not a noun while sweetening is a noun.

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

sweeten (noun)	sweetening (noun)
	the act of adding a sweetener to food
	an improvement that makes something more agreeable
	something added to foods to make them taste sweeter

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