leaving vs departure

leaving and departure both are nouns.

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

As nouns, leaving and departure are synonyms defined as:

Other synonyms of leaving include going, going away.

leaving (noun)	departure (noun)
the act of departing	the act of departing
	euphemistic expressions for death
	a variation that deviates from the standard or norm