mitigation vs diminution

mitigation and diminution both are nouns.

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

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

mitigation: to act in such a way as to cause an offense to seem less serious
diminution: the act of decreasing or reducing something

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

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

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

mitigation (noun)	diminution (noun)
to act in such a way as to cause an offense to seem less serious	the act of decreasing or reducing something
the action of lessening in severity or intensity	the statement of a theme in notes of lesser duration (usually half the length of the original)
a partial excuse to mitigate censure; an attempt to represent an offense as less serious than it appears by showing mitigating circumstances	change toward something smaller or lower