deteriorate vs decay

deteriorate is not a noun while decay is a noun.

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

As verbs, decay is a hypernym of deteriorate; that is, decay is a word with a broader meaning than deteriorate:

Other hypernyms of deteriorate include crumble, dilapidate.

deteriorate (noun)	decay (noun)
	the organic phenomenon of rotting
	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

deteriorate (verb)	decay (verb)
grow progressively worse	fall into decay or ruin
become worse or disintegrate	lose a stored charge, magnetic flux, or current
	undergo decay or decomposition