Ice boat in the context of "Rudder"

A sail is a tensile structure, which is made from fabric or other membrane materials, that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may be made from a combination of woven materials—including canvas or polyester cloth, laminated membranes or bonded filaments, usually in a three- or four-sided shape.

A sail provides propulsive force via a combination of lift and drag, depending on its angle of attack, its angle with respect to the apparent wind. Apparent wind is the air velocity experienced on the moving craft and is the combined effect of the true wind velocity with the velocity of the sailing craft. Angle of attack is often constrained by the sailing craft's orientation to the wind or point of sail. On points of sail where it is possible to align the leading edge of the sail with the apparent wind, the sail may act as an airfoil, generating propulsive force as air passes along its surface, just as an airplane wing generates lift, which predominates over aerodynamic drag retarding forward motion. The more that the angle of attack diverges from the apparent wind as a sailing craft turns downwind, the more drag increases and lift decreases as propulsive forces, until a sail going downwind is predominated by drag forces. Sails are unable to generate propulsive force if they are aligned too closely to the wind.

A windsport is any type of sport which involves wind-power, often involving a non-rigid airfoil such as a sail or a power kite. The activities can be land-based, on snow, on ice or on water. Windsport activity may be regulated in some countries by aviation/maritime authorities if they are likely to interfere with other activities. Local authorities may also regulate activity in certain areas, especially on crowded beaches and parks.

• Ice boating - using a masted sail attached to a vessel with skates
• Kite boating - sailing a boat in displacement or planing mode using a kite
• Kite landboarding - using a power kite with a wheeled board while standing
• Kite buggy - using a wheeled buggy with seats attached to a power kite
• Kite flying - flight of a small airfoil by a standing ground operator using 1-4 flying lines
• Kite skating - as for kite jumping but while using specialized skates
• Kite surfing - using a surfboard attached to a power kite
• Land sailing - a masted sail attached to a land vehicle - see also land yacht
• Sailing - navigating a boat with sail attached to a mast
• Snowkiting - skiing/snowboarding under the power of a kite
• Windsurfing - sailing using a masted sail attached via a gimbal to a surfboard
• Wing foiling or wingsurfing is a surface watersport where a rider uses a lightweight wing on a surf board with a hydrofoil.