in navigation, an assemblage of several breadths of canvas, sewed together by the lists, and edged round with cord, fastened to the yards of a ship, to make it drive before the wind. The edges of the cloths or pieces of which a sail is composed are generally sewed together with a double seam; and the whole is skirted round at the edges with a cord called the bolt-rope. Although the form of sails is extremely different, they are all nevertheless triangular or quadrilateral figures; or, in other words, their surfaces are contained either between three or four sides. The former of these are sometimes spread by a yard, as lateen-sails, and otherwise by a stay, as stay-sails, or by a mast, as shoulder-of-mutton sails; in all which cases the foremost leech or edge is attached to the said yard, mast, or stay, throughout its whole length. The latter, or those which are four-sided, are either extended by yards, as the principal yards of a ship; or by yards and booms, as the studding-sails, drivers, ring-tails, and all those sails which are set occasionally; or by gaffs and booms, as the main-sails of sloops and brigantines. (See Ship, and Ship-Building.) Sail is also a name applied to any vessel seen at a distance under sail, and is equivalent to ship. To set sail, is to unfurl and expand the sails upon their respective yards and stays, in order to begin the action of sailing. To make sail, is to spread an additional quantity of sail, so as to increase the ship's velocity. To shorten sail is to reduce or take in part of the sails, with an intention to diminish the ship's velocity. To strike sail is to lower it suddenly. This is particularly used in saluting or doing homage to a superior force, or to one whom the law of nations acknowledges as superior in certain regions. Thus all foreign vessels strike to a British man-of-war in the British seas.