one of the two basic types of sailing rig, the other being the square sail. The fore-and-aft sail, now usually triangular, is set completely aft of a mast or stay, parallel to the ship's keel, and takes the wind on either side. The mainsail always has a boom, pivoted on the mast. Historically, it represented an important advance over the ancient square sail; it first appeared in the Mediterranean as the lateen sail. Full-rigged ships carried both types of sail; modern sport sailing craft carry fore-and-aft sails exclusively because of their ready maneuverability and facility in tacking into the wind. Compare lateen sail; square sail.