drop off vs lapse

drop off is not a noun while lapse is a noun.

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

As verbs, lapse is a hyponym of drop off; that is, lapse is a word with a more specific, narrower meaning than drop off:

Other hyponyms of drop off include backslide.

drop off (noun)	lapse (noun)
	a mistake resulting from inattention
	a failure to maintain a higher state
	a break or intermission in the occurrence of something

drop off (verb)	lapse (verb)
change from a waking to a sleeping state	go back to bad behavior
fall to a lower standard	drop to a lower level, as in one's morals or standards
fall or diminish	end, at least for a long time
retreat	for time to move forward
remove (cargo, people, etc.) from and leave	pass into a specified state or condition; sink into
	let slip