drop-off vs dwindling

drop-off and dwindling both are nouns.

Word	Noun	Adjective	Verb	Adverb
drop-off	Yes	No	No	No
dwindling	Yes	Yes	No	No

As nouns, dwindling is a hyponym of drop-off; that is, dwindling is a word with a more specific, narrower meaning than drop-off:

Other hyponyms of drop-off include shrinkage, shrinking, casualty, sinking, attrition, rarefaction, dwindling away, waning.

drop-off (noun)	dwindling (noun)
a change downward	a becoming gradually less
a steep high face of rock
a noticeable deterioration in performance or quality

drop-off (adjective)	dwindling (adjective)
	gradually decreasing until little remains