moderation vs diminution

moderation and diminution both are nouns.

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

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

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

moderation (noun)	diminution (noun)
the action of lessening in severity or intensity	the act of decreasing or reducing something
quality of being moderate and avoiding extremes	the statement of a theme in notes of lesser duration (usually half the length of the original)
the trait of avoiding excesses	change toward something smaller or lower
a change for the better