farewell vs departure

farewell and departure both are nouns.

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

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

Other hypernyms of farewell include going, going away, leaving.

farewell (noun)	departure (noun)
the act of departing politely	the act of departing
an acknowledgment or expression of goodwill at parting	euphemistic expressions for death
	a variation that deviates from the standard or norm