drop-off vs drop off

drop-off is a noun but drop off is not a noun.

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

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

drop-off (verb)	drop off (verb)
	change from a waking to a sleeping state
	fall to a lower standard
	fall or diminish
	retreat
	remove (cargo, people, etc.) from and leave