diminution vs decrement

diminution and decrement both are nouns.

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

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

Other hypernyms of diminution include decrease.

diminution (noun)	decrement (noun)
the act of decreasing or reducing something	the amount by which something decreases
the statement of a theme in notes of lesser duration (usually half the length of the original)	a process of becoming smaller or shorter
change toward something smaller or lower