retrogression vs degeneration

retrogression and degeneration both are nouns.

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

As nouns, retrogression and degeneration are synonyms defined as:

retrogression and degeneration: passing from a more complex to a simpler biological form

retrogression (noun)	degeneration (noun)
returning to a former state	passing from a more complex to a simpler biological form
passing from a more complex to a simpler biological form	the process of declining from a higher to a lower level of effective power or vitality or essential quality
	the state of being degenerate in mental or moral qualities