mainsail n : the lowermost sail on the mainmast
A mainsail is the most important sail raised from the main (or only) mast of a sailing vessel.
On a square rigged vessel, it is the lowest and largest sail on the main mast.
On a fore-and-aft rigged vessel, it is the lowest and largest and often the only sail rigged aft of the main mast, and is controlled along its foot by a spar known as the boom. A sail rigged in this position without a boom is generally called a trisail, and is used in extremely heavy weather.
The modern bermuda rig uses a triangular mainsail as the only sail aft of the mast, closely coordinated with a jib for sailing upwind. A large overlapping jib or genoa is often larger than the mainsail. In downwind conditions (with the wind behind the boat) a spinnaker replaces the jib.
Traditional fore-and-aft rigs used a gaff to control the top of the mainsail, sometimes setting a topsail above it.
mainsail in Bulgarian: Грот
mainsail in Danish: Storsejl
mainsail in German: Großsegel
mainsail in Italian: Randa
mainsail in Dutch: Grootzeil
mainsail in Norwegian: Storseil
mainsail in Polish: Grot (żeglarstwo)
mainsail in Russian: Грот (парус)
mainsail in Finnish: Isopurje
mainsail in Swedish: Storsegel