decrement vs decline

decrement and decline both are nouns.

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

As nouns, decline is a hyponym of decrement; that is, decline is a word with a more specific, narrower meaning than decrement:

Other hyponyms of decrement include decay, diminution, desensitisation, desensitization, narrowing, slippage, wastage.

decrement (noun)	decline (noun)
the amount by which something decreases	a downward slope or bend
a process of becoming smaller or shorter	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

decrement (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