departure vs decease

departure and decease both are nouns.

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

As nouns, decease is a hypernym of departure; that is, decease is a word with a broader meaning than departure:

Other hypernyms of departure include death, expiry.

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

departure (verb)	decease (verb)
	pass from physical life and lose all bodily attributes and functions necessary to sustain life