exponential decay vs decline

exponential decay and decline both are nouns.

Word	Noun	Adjective	Verb	Adverb
exponential decay	Yes	No	No	No
decline	Yes	No	Yes	No

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

Other hypernyms of exponential decay include decay.

exponential decay (noun)	decline (noun)
a decrease that follows an exponential function	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

exponential decay (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