departure vs despatch

departure and despatch both are nouns.

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

As nouns, despatch is a hyponym of departure; that is, despatch is a word with a more specific, narrower meaning than departure:

departure (noun)	despatch (noun)
the act of departing	the act of sending off something
euphemistic expressions for death	killing a person or animal
a variation that deviates from the standard or norm	the property of being prompt and efficient
	an official report (usually sent in haste)

departure (verb)	despatch (verb)
	send away towards a designated goal