detumescence vs decline

detumescence and decline both are nouns.

Word	Noun	Adjective	Verb	Adverb
detumescence	Yes	No	No	No
decline	Yes	No	Yes	No

As nouns, decline is a hypernym of detumescence; that is, decline is a word with a broader meaning than detumescence:

Other hypernyms of detumescence include diminution.

detumescence (noun)	decline (noun)
diminution of swelling; the subsidence of anything swollen	a downward slope or bend
	a gradual decrease; as of stored charge or current
	change toward something smaller or lower
	a condition inferior to an earlier condition; a gradual falling off from a better state; decline

detumescence (verb)	decline (verb)
	grow smaller
	grow worse
	show unwillingness towards
	inflect for number, gender, case, etc.
	go down
	fall in value
	not accept as true