is a specific kind of: act, deed, human action, human activity.

is a broader term that covers: breaking away | farewell, leave, leave-taking, parting | French leave | disappearance, disappearing | withdrawal | sailing | boarding, embarkation, embarkment | exit | despatch, dispatch, shipment | takeoff.

derivation: depart, go, go away | depart, quit, take leave | depart, part, set forth, set off, set out, start, start out, take off.