Glider
A glider is an unpowered aircraft that sustains flight by converting altitude into forward motion and exploiting rising air to remain aloft or climb.
Gliding flight: Flight in which an aircraft moves through air without thrust from an engine. A glider is an aircraft designed to make this unpowered flight efficient.
Glider airframe: The structural body, wings, and tail of a glider, excluding its pilot and removable equipment. Its light, streamlined structure reduces the power needed to stay airborne.
Soaring: Aviation in which pilots use rising air to maintain or gain altitude without engine thrust. It is the central sport and practice built around glider flight.
Powered aircraft: Aircraft that use engines to produce thrust during flight. Unlike a glider, a powered aircraft can sustain flight with engine thrust.
Aerodynamic lift: The force perpendicular to airflow that supports an aircraft in flight. Its wings generate the force that supports the glider's weight.
Wing loading: An aircraft's weight divided by its wing area. It affects a glider's sink rate, speed, and handling in different conditions.
Glider launch methods: Techniques for getting an unpowered aircraft airborne, including towing, winching, and self-launching. A glider needs an external launch before it can exploit air currents.
Sailplane: A high-performance glider designed primarily for soaring flight. The term distinguishes purpose-built soaring aircraft from gliders designed for other roles.
Glide ratio: The horizontal distance an aircraft travels forward for each unit of altitude it loses in still air. It measures how effectively a glider turns height into distance.
Airfoil: A cross-sectional shape designed to produce aerodynamic forces as air flows around it. The glider's wing airfoil helps balance lift, drag, and performance.