An ocean liner is a passenger ship or passenger-cargo ship which transports people and often freight from one port to another along regular trans-oceanic routes according to a schedule. The term also refers to vessels designed to engage in such trades, even if temporarily used for other purposes (such as on cruises or as troopships). The category does not include ferries or other vessels engaged in short-sea trading, nor cruise ships where the voyage itself, and not transportation, is the prime purpose of the trip.