retrogress vs relapse

retrogress is not a noun while relapse is a noun.

Word	Noun	Adjective	Verb	Adverb
retrogress	No	No	Yes	No
relapse	Yes	No	Yes	No

As verbs, retrogress and relapse are synonyms defined as:

Other synonyms of retrogress include fall back, lapse, recidivate, regress.

retrogress (noun)	relapse (noun)
	a failure to maintain a higher state

retrogress (verb)	relapse (verb)
go back to bad behavior	go back to bad behavior
get worse or fall back to a previous condition	deteriorate in health