diminution vs decrease

diminution and decrease both are nouns.

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

As nouns, diminution and decrease are synonyms defined as:

Other synonyms of diminution include reduction, step-down.

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

Other hypernyms of diminution include decrement.

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

diminution (verb)	decrease (verb)
	decrease in size, extent, or range
	make become smaller