checkout vs departure time

checkout and departure time both are nouns.

Word	Noun	Adjective	Verb	Adverb
checkout	Yes	No	No	No
departure time	Yes	No	No	No

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

checkout: the latest time for vacating a hotel room
departure time: the time at which a public conveyance is scheduled to depart from a given point of origin

Other hypernyms of checkout include time of departure.

checkout (noun)	departure time (noun)
the act of inspecting or verifying	the time at which a public conveyance is scheduled to depart from a given point of origin
a counter in a supermarket where you pay for your purchases
the latest time for vacating a hotel room