deterioration vs diminution

deterioration and diminution both are nouns.

Word	Noun	Adjective	Verb	Adverb
deterioration	Yes	No	No	No
diminution	Yes	No	No	No

As nouns, diminution is a hypernym of deterioration; that is, diminution is a word with a broader meaning than deterioration:

Other hypernyms of deterioration include decline.

deterioration (noun)	diminution (noun)
process of changing to an inferior state	the act of decreasing or reducing something
a symptom of reduced quality or strength	the statement of a theme in notes of lesser duration (usually half the length of the original)
	change toward something smaller or lower