Wind once drove almost all long-distance sea trade. A sail is a large piece of fabric or other material designed to catch the wind and propel a vessel through the water.

Sails are cut and rigged in many configurations—square, fore-and-aft, lateen, and others—each with different performance on different points of sail. Modern yachts use synthetic fabrics and sophisticated controls; traditional vessels may still use canvas. Even powered ships occasionally use experimental sail or kite assistance to save fuel.

Handling sail requires skill, timing, and respect for wind strength. Reefing, trimming, and changing sail are continuous tasks in changing conditions. The language of sheets, halyards, and points of sail remains embedded in maritime culture.

• Fabric surface that converts wind into propulsive force
• Arranged in varied rig configurations
• Requires skilled handling and adjustment
• Still used for recreation and some commercial trials