regress vs retrogression

regress and retrogression both are nouns.

Word	Noun	Adjective	Verb	Adverb
regress	Yes	No	Yes	No
retrogression	Yes	No	No	No

As nouns, regress and retrogression are synonyms defined as:

Other synonyms of regress include regression, retroversion, reversion.

regress (noun)	retrogression (noun)
returning to a former state	returning to a former state
the reasoning involved when you assume the conclusion is true and reason backward to the evidence	passing from a more complex to a simpler biological form

regress (verb)	retrogression (verb)
go back to bad behavior
get worse or fall back to a previous condition
go back to a previous state
go back to a statistical means