departure vs expiration

departure and expiration both are nouns.

Word	Noun	Adjective	Verb	Adverb
departure	Yes	No	No	No
expiration	Yes	No	No	No

As nouns, departure and expiration are synonyms defined as:

Other synonyms of departure include exit, going, loss, passing, release.

departure (noun)	expiration (noun)
the act of departing	the act of expelling air from the lungs
euphemistic expressions for death	euphemistic expressions for death
a variation that deviates from the standard or norm	a coming to an end of a contract period