palliation vs diminution

palliation and diminution both are nouns.

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

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

palliation: 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 palliation include decrease, reduction, step-down.

palliation (noun)	diminution (noun)
easing the severity of a pain or a disease without removing the cause	the act of decreasing or reducing something
to act in such a way as to cause an offense to seem less serious	the statement of a theme in notes of lesser duration (usually half the length of the original)
	change toward something smaller or lower