sweeten vs mull

sweeten is not a noun while mull is a noun.

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

As verbs, mull is a hyponym of sweeten; that is, mull is a word with a more specific, narrower meaning than sweeten:

Other hyponyms of sweeten include honey, saccharify, sugar, candy, glaze, sugarcoat.

sweeten (noun)	mull (noun)
	a term used in Scottish names of promontories

sweeten (verb)	mull (verb)
make sweeter, more pleasant, or more agreeable	reflect deeply on a subject
make sweeter in taste	heat with sugar and spices to make a hot drink