propitiation vs expiation

propitiation and expiation both are nouns.

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

As nouns, propitiation and expiation are synonyms defined as:

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

Other synonyms of propitiation include atonement.

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