expiation vs propitiation

expiation and propitiation both are nouns.

Word	Noun	Adjective	Verb	Adverb
expiation	Yes	No	No	No
propitiation	Yes	No	No	No

As nouns, expiation and propitiation are synonyms defined as:

expiation and propitiation: the act of atoning for sin or wrongdoing (especially appeasing a deity)

Other synonyms of expiation include atonement.

expiation (noun)	propitiation (noun)
the act of atoning for sin or wrongdoing (especially appeasing a deity)	the act of placating and overcoming distrust and animosity
compensation for a wrong	the act of atoning for sin or wrongdoing (especially appeasing a deity)