atonement vs reparation

atonement and reparation both are nouns.

Word	Noun	Adjective	Verb	Adverb
atonement	Yes	No	No	No
reparation	Yes	No	No	No

As nouns, reparation is a hyponym of atonement; that is, reparation is a word with a more specific, narrower meaning than atonement:

atonement: the act of atoning for sin or wrongdoing (especially appeasing a deity)
reparation: something done or paid in expiation of a wrong

Other hyponyms of atonement include amends.

atonement (noun)	reparation (noun)
the act of atoning for sin or wrongdoing (especially appeasing a deity)	something done or paid in expiation of a wrong
compensation for a wrong	the act of putting something in working order again
	(usually plural) compensation exacted from a defeated nation by the victors
	compensation (given or received) for an insult or injury