reduction vs diminution

reduction and diminution both are nouns.

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

As nouns, reduction and diminution are synonyms defined as:

Other synonyms of reduction include decrease, step-down.

reduction (noun)	diminution (noun)
the act of decreasing or reducing something	the act of decreasing or reducing something
the act of reducing complexity	the statement of a theme in notes of lesser duration (usually half the length of the original)
any process in which electrons are added to an atom or ion (as by removing oxygen or adding hydrogen); always occurs accompanied by oxidation of the reducing agent	change toward something smaller or lower