degeneration vs retrogression

degeneration and retrogression both are nouns.

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

As nouns, degeneration and retrogression are synonyms defined as:

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

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