drop-off vs modification

drop-off and modification both are nouns.

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

As nouns, modification is a hypernym of drop-off; that is, modification is a word with a broader meaning than drop-off:

drop-off: a change downward
modification: an event that occurs when something passes from one state or phase to another

Other hypernyms of drop-off include alteration, change.

drop-off (noun)	modification (noun)
a change downward	the act of making something different (as e.g. the size of a garment)
a steep high face of rock	slightly modified copy; not an exact copy
a noticeable deterioration in performance or quality	an event that occurs when something passes from one state or phase to another
	the grammatical relation that exists when a word qualifies the meaning of the phrase