abiotrophy vs retrogression

abiotrophy and retrogression both are nouns.

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

As nouns, retrogression is a hypernym of abiotrophy; that is, retrogression is a word with a broader meaning than abiotrophy:

abiotrophy: a loss of vitality and a degeneration of cells and tissues not due to any apparent injury
retrogression: passing from a more complex to a simpler biological form

Other hypernyms of abiotrophy include degeneration.

abiotrophy (noun)	retrogression (noun)
a loss of vitality and a degeneration of cells and tissues not due to any apparent injury	returning to a former state
	passing from a more complex to a simpler biological form