| abeam | Directly to one side of the boat, 90 degrees to the right or left of the bow. |
| aft | Behind the boat, also, the area at the rear of the boat. |
| alternator | A device attached to the engine that generates electricity. |
| anchor | A metal contrivance designed to hold the boat at rest by grabbing the bottom of an anchorage. |
| auto pilot | A device for automatically keeping a boat on course. |
| back | (1) Make the boat stop by reversing the wind across the sails. (2) (Concerning wind) Rotate in a counterclockwise direction (Northern hemisphere). Also see veer. |
| backstay | The wire between the mast and the aft end of the boat. |
| ballast | A weight in the keel, usually lead, that holds the boat upright. |
| bar | A collection of debris at the entrance to a bay fed by a river, often shallow and dangerous. |
| barometer | A device for measuring atmospheric pressure, usually calibrated in millibars. |
| berth | A small bed. |
| boathook | An implement with which to grab things or push them away. |
| boom | A horizontal bar that supports the bottom of a sail and determines its shape. |
| bosun's chair | A seat, usually canvas, used to raise a sailor up a mast. |
| bow | The forward part of a boat. |
| bowline | A useful knot. |
| bungee cord | An elastic cord, usually with hooks on the ends. |
| cast off | To leave a dock, in particular to release and gather dock lines. |
| close reach | A point of sail close to the wind. See pinch. |
| cockpit | An area at the aft end from which one controls the boat. |
| cqr | A popular kind of anchor, meant to sound like "secure." |
| danforth | A type of anchor that sometimes has a holding power greater than its size. And sometimes less. |
| deck | The top outside surface of the boat. |
| degree | 1/360th of a full circle. Ninety degrees is a complete turn to the right or left. One hundred eighty degrees is a reversal of course. |
| depth sounder | An electronic device resembling sonar that gauges the depth of the water. |
| diesel | (1) A type of engine popular on boats. (2) The fuel that powers diesel engines. |
| dinghy | A small boat used to travel in depths too shallow for a sailboat. Some are inflatable, some are wood or molded plastic. |
| double-ender | A sailboat that has the shape of a canoe, pointed at the front and back. |
| downwind | A point of sail in which the wind blows from aft, an easy sail. |
| drive shaft | A rod that connects the engine to the propeller. See prop. |
| fax | (1) A method for transmitting pictures by radio or telephone. (2) A picture received by means of fax. |
| fix | A position obtained by sextant or navigation receiver. See sextant, satnav, gps. |
| galley | A boat's kitchen. |
| genoa | A large jib. See jib. |
| gmt | Greenwich Mean Time, the time in Greenwich, England. The standard time used on a boat for navigation and other purposes. |
| gps | Global Positioning System. A relatively new navigation system using satellites — not to be confused with satnav. |
| halyard | A line used to raise sails up the mast. |
| ham radio | (1) A radio transceiver used in the Amateur Radio Service. (2) A licensing and frequency allocation scheme by which non-professional radio operators ("hams") can transmit and receive radio messages. |
| hank, unhank | (noun) A fastener by which a sail can be attached to a wire. (verb) To connect or disconnect a sail from a wire. |
| harness | A safety system consisting of a body harness and lines on deck to allow movement around the boat without great risk of falling overboard. |
| hatch | A usually watertight cover or doorway. |
| head | A boat's bathroom. |
| headsail | The forward-most sail on a boat. See jib. |
| headstay | The wire between the mast and the bow of the boat. |
| headway | Progress, usually against contrary winds. |
| headwind | An adverse wind, usually from the desired direction of travel. |
| heave to | Arrange the boat and sails to ride comfortably and move as little as possible. |
| hf | High Frequency, the range of radio frequencies between 3 and 30 megahertz, used in long-distance marine communications. |
| high | (weather) a high-pressure system, characterized by a clockwise wind pattern (in the Northern Hemisphere) and generally clear and pleasant weather. See low. |
| hull | The basic watertight structure of the boat, in particular that part below the waterline. |
| inverter | An electronic device that converts battery power to AC house current. |
| jib | Usually the sail closest to the bow of a boat, usually an efficient sail. |
| jibe | To change course while sailing downwind so that the wind changes sides. Somewhat dangerous in high wind, and hard on the boom and sails. See preventer. |
| keel | A fin at the bottom of the hull that prevents the boat from moving sideways in the water. The keel also converts the sideways pressure of the wind into forward boat movement. |
| knot | (1) Any of the useful tangles of line that keeps things attached. (2) A measure of speed on a boat, calibrated in nautical miles. |
| knot meter | A usually electronic device to measure speed through the water. |
| leeway | (1) The amount of sideways motion through the water allowed by the keel, usually undesirable. (2) The open space between the boat and land in the downwind direction, a safety margin. |
| lie ahull | Take down all sails and let the boat drift where it will. |
| life raft | A small emergency boat, usually inflatable. |
| line | What a rope is called while on a boat. See rope. |
| loran | A short-range system for navigation that uses shore transmitters. |
| low | (weather) a low-pressure system, characterized by a counterclockwise wind pattern (in the Northern Hemisphere), generally cloudy, rainy weather, and rough seas. See high. |
| magnetron | A vacuum tube surrounded by a magnet that generates microwave energy. Used in radar sets and microwave ovens. |
| mainsail | The sail that is hanked onto the mast and the boom. On my boat, the aftmost sail. |
| mast | The principal support member, held up by the rigging, that holds the sails aloft. |
| meltemi | A strong wind in the Mediterranean. |
| millibar | A measure of atmospheric pressure. See barometer. |
| nautical mile | Exactly one minute (1/60 of a degree) of angle on the earth, a size chosen so that angles measured with a sextant can be easily converted into distances. Equal to 6076 feet and change. 1 nautical mile = 1.15 statute mile. |
| pacific high | A high-pressure system in the Eastern Pacific that provides reasonably reliable winds between the West Coast of the U.S. and Hawaii. |
| painter | A line that secures a dinghy. |
| pinch | A point of sail very near the wind, not usually fast or efficient. |
| port | (1) (direction) Left. (2) An opening in the side of the boat (also porthole). |
| porthole | An opening for light and ventilation, usually watertight when closed. |
| preventer | A line rigged to hold something in place, usually used to keep the boom from changing sides unexpectedly. See jibe. |
| prop | The propeller that is attached to the engine by way of the drive shaft. See drive shaft. |
| receiver | Any of several kinds of radio receiver used for communication or navigation. See satnav, loran, gps, ham radio. |
| rem | Rapid Eye Movement, a kind of sleep accompanied by dreams. Indicates lengthy uninterrupted sleep. |
| rigging | A system of wires that supports the mast. |
| rode | A chain, rope or both that attaches an anchor to the boat. |
| rope | What a line is called before it is taken onto a boat. See line. |
| rudder | A paddle in the water, attached to a wheel or tiller in the cockpit, that controls the boat's direction. |
| sail | A piece of cloth, attached to the boat by means of a halyard and one or more sheets and sometimes a boom, that moves the boat by way of wind power. |
| satnav | A method of satellite navigation, also a receiver used for this purpose. Nearly obsolete. See gps. |
| sextant | An optical sighting device that determines the angle between a celestial body and the horizon. Used for navigation. See also satnav, gps. |
| sheet | (noun) A line that controls the position of a sail. (verb) To adjust a sail. |
| solar panel | A large, rectangular device that converts sunlight directly into electricity with no moving parts. See wind generator. |
| spreader | A horizontal metal bar on the mast that holds some of the supporting wires and increases the stiffness of the mast. See rigging. |
| starboard | (direction) Right. |
| staysail | A small third sail (on my boat) between the foresail or jib and the mainsail. |
| tack | (verb) Change directions so that the wind comes from the opposite side of the boat. (noun) Port tack, wind from left — starboard tack, wind from right. |
| throttle | A lever in the cockpit that adjusts the engine's speed. |
| trade wind | A reliable wind in the tropics that blows from the East. |
| transceiver | A radio transmitter-receiver, usually equipped with a microphone. |
| upwind | A usually difficult sail against the wind. |
| veer | (in reference to wind) Rotate in a clockwise direction (Northern hemisphere). Also see back. |
| vhf | Very High Frequency, the range of radio frequencies between 30 and 300 megahertz, used in short-range marine communications. Also a radio transceiver that uses these frequencies. |
| vmg | Velocity Made Good, the boat's true velocity after factors such as leeway and ocean currents are taken into account. |
| waterline | (1) The place on the hull the water just reaches when the boat is at rest. (2) (slang) The length of the hull at the waterline. |
| waypoint | An arbitrary position used in navigation. |
| weathervane | (noun) A mechanical wind direction indicator. (verb) To turn into the wind, usually while out of control. |
| whisker pole | A rigid pole used to spread the jib out on a downwind sail. |
| winch | A mechanical drum used to apply or maintain high forces on halyards and sheets. |
| wind surf | (verb) Ride a small fiberglass board with an attached mast and sail. A lot of fun. |
| wind vane | A mechanical device that holds the boat on a fixed course relative to the wind. |
| windmill | A propeller mounted on a pole that converts wind power into electricity. |
| wing-and-wing | A downwind sailing arrangement in which the mainsail is deployed on one side and the jib on the other. |
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