A fare is the fee paid by a passenger for use of a public transport system: rail, bus, taxi, etc. In the case of air transport, the term airfare is often used. Fare structure is the system set up to determine how much is to be paid by various passengers using a transit vehicle at any given time. A linked trip is a trip from the origin to the destination on the transit system. Even if a passenger must make several transfers during a journey, the trip is counted as one linked trip on the system.