decrement vs decay

decrement and decay both are nouns.

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

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

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

decrement (noun)	decay (noun)
the amount by which something decreases	the organic phenomenon of rotting
a process of becoming smaller or shorter	a gradual decrease; as of stored charge or current
	the process of gradually becoming inferior
	the spontaneous disintegration of a radioactive substance along with the emission of ionizing radiation
	an inferior state resulting from the process of decaying

decrement (verb)	decay (verb)
	fall into decay or ruin
	lose a stored charge, magnetic flux, or current
	undergo decay or decomposition