depletion vs diminution

depletion and diminution both are nouns.

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

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

Other hypernyms of depletion include decrease, reduction, step-down.

depletion (noun)	diminution (noun)
the act of decreasing something markedly	the act of decreasing or reducing something
the state of being depleted	the statement of a theme in notes of lesser duration (usually half the length of the original)
	change toward something smaller or lower