Aft: At, in, toward or close to the stern (rear).

Backstay: A mast support that runs from the top of the mast to the stern of the boat. It may be adjustable in order to bend the mast backward or to increase tension on the Forestay tool.

Ballast: Weight in the keel of a boat that adds stability.

Beam: A boat's greatest width.

Beating: Sailing (or pointing) at an angle into the wind or upwind. Since sailboats cannot sail directly into the wind, "beating" is the closest course to the wind they can sail.

Bilge: The lowest part of a boat's hull.

Blanketing: A tactical maneuver in which one boat slows a competitor by positioning itself to obstruct the competitor's wind.

Block: An assemblage of one or more sheaves (pulleys) housed in a plastic or metal case that changes the direction of travel of a line (rope) and may be attached to a boat's deck, spar or other stationary object.

BoomSpar to which a sail's lower edge or foot is attached. The boom is attached to the mast at the gooseneck.

Boom vang: Lines that control the boom. These lines run from the boom to the base of the mast and are used when reaching and running.

Bow: The front of the boat.

Broach: When in a downwind situation, the boat turns uncontrollably and is pushed by the wind onto its side, lying with the mast parallel to the water. As a rule, the boat will right itself.

Buoy: A floating marker.

Cam cleat: A mechanical cleat used to hold a line automatically. It uses two spring-loaded cams that come together to clamp their teeth on the line, which is placed between them. Also known as jam cleat.

Centerboard: Like a keel, it is a weighted appendage projecting below the boat that keeps it from capsizing and also supplies the hydrodynamic lateral force that enables the boat to sail upwind. Unlike a keel, it is retractable.

Cleat: A fitting, typically with projecting ends, that holds a line against the tension from the sails, rigging or mooring.

Clew: The lower corner of a mainsail or jib and either lower corner of a spinnaker.

Coming about: Turning the boat so the bow crosses through the eye of the wind, thereby changing the side of the yacht on which the sails are carried. Also known as tacking.

Covering: A tactical maneuver in which a boat stays between a competitor and the wind or the next mark.

Daggerboard: An adjustable fin primarily used to stop the boat moving sideways through the water. Also known as centerboard.

Dinghy: Laser, Laser Radial, 470, Finn - the dinghies used at the Olympics - they all have one hull and a centreboard or daggerboard.

Downwind: The point of sail when the wind blows from aft of the boat's beam.

Drag: The negative or retarding force acting on a body, such as a boat moving through a fluid parallel and opposite to the direction of motion.

Fall off: A maneuver in which a boat turns away from the wind.

Fleet Racing: Competition format were entries race against each other around a course.

Foot: The bottom edge of a sail.

Genoa/Headsail/Jib: The smaller sail set in front of the mast.

Gooseneck: A fitting that attaches the boom to the mast.

Gybe: Turning the boat so the stern crosses through the eye of the wind, (thereby changing the side of the boat on which the sails are carried (opposite of tacking). Also spelled jibe.

Halyard: A line used to hoist and hold up a sail.

Header: Wind shift that causes the boat to head away from the mark.

Helmsman: The crew member who steers the boat; also the skipper, or the "driver."

Hiking out: Leaning out of the craft in order to change the center of gravity in the boat and go faster.

Hiking straps: Straps attached to the feet that help a sailor hike out more, minimizing the chance of falling out of the boat.

Hull: The main body or shell of a ship or other vessel, including the bottom, sides, and deck.

ISAF: International Sailing Federation, the world governing body of sailboat racing.

Jam cleat: A device used to grip a line (rope). It has two rows of V-shaped molded teeth that grip the line when it is jammed in the groove. Also known as cam cleat.

Jib: A foresail that overlaps the shroud base and is used for sailing upwind.

Jibe: Same as the gybe -- turning the boat so the stern crosses through the eye of the wind, thereby changing the side of the yacht on which the sails are carried (opposite of tacking).

Keel: A weighted, non-moveable appendage projecting below the boat that keeps it from capsizing and also supplies the hydrodynamic lateral force that enables the boat to sail upwind.

Kite: Large, light ballooning sails that are only attached to the mast at the corners. They are used when sailing downwind. Also known as spinnaker.

Knot: One nautical mile per hour.

Lay: To sail a course that clears an object or racecourse marker buoy such as the windward and leeward marks. When a boat is doing so, it is said to be "laying the mark."

Layline: An imaginary line projecting at an angle and corresponding to the wind direction from either side of a racecourse marker buoy that defines the optimum sailing angle for a boat to fetch the mark or the finish line. When a boat reaches this point, it is said to be "on the layline." Going beyond the layline means the boat is sailing a greater distance to reach the mark or finish line.

Leech: The trailing edge of a sail or the curve of a sail.

Leeward: The side furthest away from the wind.

Lines: A nautical term for ropes.

Luff, to: Bubbling or flapping of a sail when it is not trimmed enough or is being back winded by another sailor when the course sailed is too close to the wind.

Mainsail: The sail behind the mast.

Mark: A buoy used in a racecourse.

Mast: The vertical spar that holds up the sails.

Match racing: A racing format in which only two boats compete at a time, as opposed to fleet racing, wherein three or more boats sail at once.

Medal Race: The final race in the series. Only the top 10 boats after the opening series compete and scores are doubled.

Multihull: Nacra 17 (boat used in its inaugural event at the 2016 Rio Olympic Games) - A boat with more than one hull. A boat with two hulls is also known as a catamaran and a boat with three hulls is knows as a trimaran.

Nautical mile: The unit of geographical distance used on saltwater charts; one nautical mile equals 6,076 feet or 1.15 statute miles. Therefore, one statute mile equals 0.87 of a nautical mile.

Off the wind: Sailing away from the wind; also downwind, reaching or running.

Plane: A boat planes when she sails over her own bow wave so only a small section of the hull is in the water. This allows the boat to go faster than the theoretical maximum hull speed.

Pointing: Sailing at an angle into the wind or upwind. Depending on a boat's design, some will "point higher" or sail more directly into the wind and thus sail a shorter course to a given mark on the racecourse.

Port: Nautical term for the left side of a boat when facing forward.

Port tack: Sailing with the wind blowing onto the port side and the mainsail on the starboard side.

Race Officials: The officials responsible for running the race and enforcing the rules. This group includes the measurers who ensure that each sailor's equipment is equal and within the rules, the race officers who run the races and the judges and umpires who are rules experts and make decisions about whether rules have been broken.

Reef: To decrease a sail's size.

Rigging: The wires, lines, halyards and other items used to attach the sails and the spars to the boat. The lines that do not have to be adjusted often are known as standing rigging. The lines that are adjusted to raise, lower and trim the sails are known as running rigging.

Rudder: A moveable fin located underneath the back of the boat that steers the craft.

Running rigging: All moving rods and lines that support and control the mast and sails.

Shackle: A metal connector that attaches to other fittings with the use of a pin that is inserted through the arms of a U.

Sheet: A line that controls sails.

Skiff: 49er - A light open dinghy with a self-draining hull.

Slalom finish: A technical section of the windsurfing (RS:X) course involving multiple changes of direction in quick succession.

Spar: A basic term for a mast, boom or yard.

Spinnaker: Large, light ballooning sails that are only attached to the spars at the corners. They are used when running or reaching, sailing downwind.

Starboard: Nautical term for the right half of the boat when facing forward.

Starboard tack: Sailing with the wind blowing onto the starboard side and the mainsail on the port side.

Stern: The rear of the boat.

Tacking: Turning the boat so the bow crosses through the eye of the wind, thereby changing the side of the boat on which the sails are carried (opposite of gybing).

Tiller: A lever used to turn the rudder of a boat from side to side.

Trapeze: To stand on the side of the boat to maximize the effect of the body weight.

Trim: To adjust the sail to the right shape and angle to the wind. The process of "hiking out," or changing the center of gravity of the boat in order to go faster.

Upwind: Toward the direction from which the wind blows; windward.

Way: Forward motion of a boat. A term typically used in the context of saying that a boat is making way, is underway, or has way on.

Windward: The side closest to the wind.