drop off vs diminish

drop off and diminish both are verbs.

Word	Noun	Adjective	Verb	Adverb
drop off	No	No	Yes	No
diminish	No	No	Yes	No

As verbs, diminish is a hypernym of drop off; that is, diminish is a word with a broader meaning than drop off:

Other hypernyms of drop off include decrease, fall, lessen.

drop off (verb)	diminish (verb)
change from a waking to a sleeping state	decrease in size, extent, or range
fall to a lower standard	lessen the authority, dignity, or reputation of
fall or diminish
retreat
remove (cargo, people, etc.) from and leave