lapse vs backslide

lapse is a noun but backslide is not a noun.

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

As verbs, lapse and backslide are synonyms defined as:

lapse and backslide: drop to a lower level, as in one's morals or standards

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

lapse (verb)	backslide (verb)
go back to bad behavior	drop to a lower level, as in one's morals or standards
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