Aft: The rear of a boat, close to the stern

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

Boom: Spar 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: The Laser, Laser Radial, 470, and Finn are all dinghies that have been used in Olympic sailing - 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 it 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