Coupon a passenger boarding a flight at one airport and deplaning at another; may be the only flight on a ticket or one of many; the passenger may remain on the plane during a stopover. Named after the boarding pass you hand a flight attendant to board. 

Flight a plane taking off at one airport and landing at another. 

Itinerary the specific routing that gets the passenger from his True Origin to his True Destination (see definition of “true O&D” below). E.g., True OD = IAD – HNL; Itinerary = IAD-SFO-HNL.

Segment a single flight with 0, 1 or multiple stops but the same flight number. Like a coupon, a passenger boards a plane and deplanes at some other airport, possibly staying on the plane at intermediate stops. This definition is from IATA. Even industry people often mix using segment and sector, but this is only true when the segment is a non-stop flight. Please note that in the US DOT data such as T100, segment data refers to sectors while market data refers to our segment definition. 

Sector a single flight leg from one runway to another. There’s a new sector every time the wheels touch the ground and then lift up again. aka “leg”.

Sector O&D the origin and destination airport of each flight sector on a trip. Usually, the same as the coupon O&D unless the coupon is for a one-stop flight (same flight number but with a stop). 

Ticket one or many coupons, linked together, generated when a passenger purchases a flight service. It can be a one-way ticket from A to B or a round-trip ticket from A to B then back to A. 

Trip – aka “journey”- a set of flights, one or many, taking a passenger from origin to destination. When a passenger purchases a round-trip ticket, it usually contains two trips, one from A to B and another from B back to A.  

True O&D where a passenger is really coming from and going to, without regard to the connecting points along the way. A True O&D is sometimes called just an O&D, or even a Trip.