relapsing vs lapse

relapsing and lapse both are nouns.

Word	Noun	Adjective	Verb	Adverb
relapsing	Yes	No	No	No
lapse	Yes	No	Yes	No

As nouns, relapsing and lapse are synonyms defined as:

Other synonyms of relapsing include backsliding, lapsing, relapse, reversion, reverting.

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

relapsing (verb)	lapse (verb)
	go back to bad behavior
	drop to a lower level, as in one's morals or standards
	end, at least for a long time
	for time to move forward
	pass into a specified state or condition; sink into
	let slip