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Above-water hull
The hull section of a vessel above waterline, the visible part of a ship. Also, topsides.

Toward the stern, relative to some object (e.g., abaft the helm).

A relative bearing at right angles to the centerline of the ship's keel.

Accommodation ladder
A portable flight of steps down a ship's side.

Afloat and unattached in any way to the shore or seabed, but not under way. It implies that a vessel is not under control and therefore goes where the wind and current take her (loose from moorings, or out of place). Also refers to any gear not fastened down or put away properly.

Towards the stern of the vessel.

Of a vessel which is floating freely (not aground or sunk). More generally of vessels in service (e.g., the community has 10 Xmarans afloat).

Resting on or touching the ground or bottom.

Forward of the bow.

Condition when a vessel is broadside to oncoming waves.

Structural member connecting the amas to the vaka in a trimaran.

In the rigging of a sailing ship. Above the ship's uppermost solid structure; overhead or high above.

The two outer (outrigger) hulls of a trimaran.

Amidships (or midships)
In the middle portion of ship, along the line of the keel.

An object designed to prevent or slow the drift of a ship, attached to the ship by a line or chain; typically a metal, hook-like or plough-like object designed to grip the bottom under the body of water (but also see sea anchor).

A suitable place for a ship to anchor. Area of a port or harbor.

Anchor ball
Round black shape hoisted in the forepart of a vessel to show that it is anchored.

Anchor buoy
A small buoy secured by a light line to anchor to indicate position of anchor on bottom.

Anchor chain or anchor cable
Chain connecting the ship to the anchor.

Anchor light
White light displayed by a ship at anchor. Two such lights are displayed by a ship over {{convert|150|ft|m}} in length.

Anchor rode
The anchor line, rope or cable connecting the anchor chain to the vessel. Also Rode.

Apparent wind
The combination of the true wind and the headwind caused by the boat's forward motion. For example, it causes a light side wind to appear to come from well ahead of the beam.

A ship's weapons.

On the beach, shore or land.

towards the stern (rear) of a vessel, behind a vessel.

Athwart, athwartships
At right angles to the fore and aft or centerline of a ship

So low in the water that the water is constantly washing across the surface.

Position of an anchor just clear of the bottom.


Long lines or cables, reaching from the stern of the vessel to the mast heads, used to support the mast.

A soft covering for cables (or any other obstructions) that prevents sail chafing from occurring.

A lighted or unlighted fixed aid to navigation attached directly to the earth’s surface. (Lights and daybeacons both constitute beacons.)

Sailing closer to the wind than about 60° (see also reaching, running and tacking).

Beaufort scale
The scale describing wind force devised by Admiral Sir Francis Beaufort, in which winds are graded by the effect of their force (originally, the amount of sail that a fully-rigged frigate could carry). Scale now reads up to Force 17.

Belaying pins
Bars of iron or hard wood to which running rigging may be secured, or belayed.

A knot used to join two ropes or lines. Also see hitch.

Bermuda rig
A triangular mainsail, without an upper spar, which is hoisted up the mast by a single halyard attached to the head of the sail. This configuration, introduced to Europe about 1920, allows the use of a tall mast, enabling sails to be set higher where wind speed is greater.

1. A location in a port or harbor used specifically for mooring vessels while not at sea.
2. A bed or sleeping accommodation on a boat or ship.

A loop in rope or line tied in the middle of a rope, without access to the ends.

The bilge is the compartment at the bottom of the hull of a ship or boat where water collects so that it may be pumped out of the vessel at a later time.

Bilge keels
A pair of keels on either side of the hull, usually slanted outwards. In yachts, they allow the use of a drying mooring, the boat standing upright on the keels (and often a skeg) when the tide is out.

Bimini top
Open-front canvas top for the cockpit of a boat, usually supported by a metal frame.

The stand on which the ship's compass is mounted.

A post mounted on the ship's bow, for fastening ropes or cables.

A pole with a hook on the end, used to reach into the water to catch buoys or other floating objects.

A stay which holds the bowsprit downwards, counteracting the effect of the forestay. Usually made of wire or chain to eliminate stretch.

Body plan
An end elevation (view) showing the contour of the sides of a ship at certain points of her length.

Booby hatch
A sliding hatch or cover.

A spar attached to the foot of a fore-and-aft sail.

Boom gallows
A raised crossmember that supports a boom when the sail is lowered (obviates the need for a [topping lift]]).

Boom vang
A sail control that lets one apply downward tension on a boom, countering the upward tension provided by the sail. The boom vang adds an element of control to sail shape when the sheet is let out enough that it no longer pulls the boom down. Boom vang tension helps control leech twist, a primary component of sail power.

Pledging a ship as security in a financial transaction.

The front of a ship.

A type of knot, producing a strong loop of a fixed size, topologically similar to a sheet bend. Also a rope attached to the side of a sail to pull it towards the bow (for keeping the windward edge of the sail steady).

A spar projecting from the bow used as an anchor for the forestay and other rigging.

The handle of the pump, by which it is worked.

A structure above the weather deck, extending the full width of the vessel, which houses a command centre, itself called by association, the bridge.

When a sailing vessel loses control of its motion and is forced into a sudden sharp turn, often heeling heavily and in smaller vessels sometimes leading to a capsize. The change in direction is called broaching-to. Occurs when too much sail is set for a strong gust of wind, or in circumstances where the sails are unstable.

An upright wall within the hull of a ship. Particularly a watertight, load-bearing wall.

The extension of the ship's side above the level of the weather deck.

1. A spar, similar to a bowsprit, but which projects from the stern. May be used to attach the backstay or mizzen sheets.
2. An iron bar (projecting out-board from a ship's side) to which the lower and topsail brace blocks are sometimes hooked.

A floating object of defined shape and color, which is anchored at a given position and serves as an aid to navigation.

A small flag, typically triangular, flown from the masthead of a yacht to indicate yacht-club membership.


An enclosed room on a deck or flat.

Cable length
A measure of length or distance. Equivalent to (UK) 1/10 nautical mile, approx. 600 feet; (USA) 120 fathoms, 720 feet (219 m); other countries use different values.

A type of antipersonnel cannon load in which lead balls or other loose metallic items were enclosed in a tin or iron shell. On firing, the shell would disintegrate, releasing the smaller metal objects with a shotgun-like effect.

Canoe stern
A design for the stern of a yacht which is pointed, like a bow, rather than squared off as a transom.

When a ship or boat lists too far and rolls over, exposing the keel. On large vessels, this often results in the sinking of the ship.

A large winch with a vertical axis. A full-sized human-powered capstan is a waist-high cylindrical machine, operated by a number of hands who each insert a horizontal capstan bar in holes in the capstan and walk in a circle. Used to wind in anchors or other heavy objects.

Tilting a ship on its side, usually when beached, to clean or repair the hull below the water line.

To prepare an anchor, after raising it by lifting it with a tackle to the cat head, prior to securing (fishing) it alongside for sea. (An anchor raised to the cat head is said to be catted.)

A vessel with two hulls.

A cat-rigged vessel with a single mast mounted close to the bow, and only one sail, usually on a gaff.

Cat head
A beam extending out from the hull used to support an anchor when raised in order to secure or 'fish' it.

A board or plate lowered through the hull on the centerline to resist leeway.

Wear on line or sail caused by constant rubbing against another surface.

Chafing gear
Material applied to a line or spar to prevent or reduce chafing. See Baggywrinkle.

Chain locker
A space in the forward part of the ship, typically beneath the bow in front of the foremost collision bulkhead, that contains the anchor chain when the anchor is secured for sea.

Chain-wale or channel
A broad, thick plank that projects horizontally from each of a ship's sides abreast a mast, distinguished as the fore, main, or mizzen channel accordingly, serving to extend the base for the shrouds, which supports the mast.

Wooden blocks at the side of a spar.

1. A relatively sharp angle in the hull, as compared to the rounded bottoms of most traditional boat hulls.
2. A line formed where the sides of a boat meet the bottom. Soft chine is when the two sides join at a shallow angle, and hard chine is when they join at a steep angle.

A stationary device used to secure a rope aboard a vessel.

A method of fixing together two pieces of wood, usually overlapping planks, by driving a nail through both planks as well as a washer-like rove. The nail is then burred or riveted over to complete the fastening.

The lower corner(s) of a sail at the end(s) of the boom.

Used to truss up the clews, the lower corners of square sails.

Close aboard
Near a ship.

Of a vessel beating as close to the wind direction as possible.

The raised edge of a hatch, cockpit or skylight to help keep out water.

A raised and windowed hatchway in the ship's deck, with a ladder leading below and the hooded entrance-hatch to the main cabins.

The part of the stern above the waterline that extends beyond the rudder stock culminating in a small transom. A long counter increases the waterline length when the boat is heeled, so increasing hull speed.

Courses the lowest square sail on each mast– The mainsail, foresail, and the mizzen on a four masted ship (the after most mast usually sets a gaff driver or spanker instead of a square sail).

Crance/Crans/Cranze iron
A fitting, mounted at the end of a bowsprit to which stays are attached.

A rope loop, usually at the corners of a sail, for fixing the sail to a spar. They are often reinforced with a metal eye.

A square yard used to spread the foot of a topsail where no course is set, e.g. on the foremast of a topsail schooner or above the driver on the mizzen mast of a ship rigged vessel.

Crow's nest
Specifically a masthead constructed with sides and sometimes a roof to shelter the lookouts from the weather, generally by whaling vessels, this term has become a generic term for what is properly called masthead. See masthead.

Cross Trees
A strong cross piece that allows to spread the top mast stays allowing for taller masts, larger top sails. Allows to extend the height of the ships mast.

Metal Y shaped pins to hold oars whilst rowing.

Cut splice
A join between two lines, similar to an eye-splice, where each rope end is joined to the other a short distance along, making an opening which closes under tension.


A type of light centerboard that is lifted vertically; often in pairs, with the leeward one lowered when beating.

A wooden block with holes which is spliced to a shroud. It is used to adjust the tension in the [standing rigging]] of large sailing vessels, by lacing through the holes with a lanyard to the deck. Performs the same job as a turnbuckle.

The design angle between the keel and horizontal.

A wooden part of the centerline structure of a boat, usually between the sternpost and amidships.

the structures forming the approximately horizontal surfaces in the ship's general structure. Unlike flats, they are a structural part of the ship.

Deck hand
A person whose job involves aiding the deck supervisor in (un)mooring, anchoring, maintenance, and general evolutions on deck.

The under-side of the deck above. Sometimes paneled over to hide the pipe work. This paneling, like that lining the bottom and sides of the holds, is the ceiling.

A lifting device composed of one mast or pole and a boom or jib which is hinged freely at the bottom.

The the weight of water equivalent to the immersed volume of a ship's hull.

Displacement hull
A hull designed to travel through the water, rather than planing over it.

Also called the "equatorial calms", is a nautical term for the equatorial trough, with special reference to the light and variable nature of the winds.

A structure consisting of a number of piles driven into the seabed or riverbed in a circular pattern and drawn together with wire rope.

A line used to control either a mobile [spar]], or the shape of a sail.

The depth of a ship's keel below the waterline.

The large sail flown from the mizzen gaff.

1. Loose packing material used to protect a ship's cargo from damage during transport.
2. Personal baggage.


Small lines, by which the uppermost corners of the largest sails are secured to the yardarms.

Echo sounding
Measuring the depth of the water using a [sonar]] device. Also see sounding and swinging the lead.


1. A smooth curve, usually referring to a line of the hull which has no deviations.
2. To make something flush.
3. A rope is fair when it has a clear run.
4. A wind or current is fair when it offers an advantage to a boat.

Fall Off
To change the direction of sail so as to point in a direction that is more down wind. To bring the bow leeward. Also bear away, bear off or head down. The opposite of heading up.

A unit of length equal to {convert|6|ft|m}, roughly measured as the distance between a man's outstretched hands. Particularly used to measure depth.

An air or foam filled bumper used in boating to keep boats from banging into docks or each other.

Reinforced concrete, constructed of hydraulic cement mortar reinforced with closely spaced layers of continuous and relatively small diameter wire mesh made of metal or other suitable material.

1. The distance of open water across which winds or waves have traveled.
2. To reach a mark without tacking.

1. A tapered wooden tool used for separating the strands of rope for splicing.
2. A bar used to fix an upper mast in place.

Fire ship
A ship loaded with flammable materials and explosives and sailed into an enemy port or fleet either already burning or ready to be set alight by its crew (who would then abandon it) in order to collide with and set fire to enemy ships.

1. To repair a mast or spar with a fillet of wood.
2. To secure an anchor on the side of the ship for sea (otherwise known as "catting".)

Fixed propeller
A propeller mounted on a rigid shaft protruding from the hull of a vessel, usually driven by an inboard motor; steering must be done using a rudder. See also outboard motor and sterndrive.

The maximum speed of a ship. Faster than "full speed".

1. A curvature of the topsides outward towards the gunwale.
2. A pyrotechnic signalling device, usually used to indicate distress.

Debris or cargo that remains afloat after a shipwreck. See also jetsam.

The wedge-shaped part of an anchor's arms that digs into the bottom.

Folding propeller
A propeller with folding blades, furling to reduce drag on a sailing vessel when not in use.

Following sea
Wave or tidal movement going in the same direction as a ship

1. The lower edge of any sail.
2. The bottom of a mast.
3. A measurement of 12 inches.

Fore, foreward
Towards the bow (of the vessel).

The lower part of the stem of a ship.

Long lines or cables, reaching from the bow of the vessel to the mast heads, used to support the mast.

The opposite of clear. For instance, a rope is foul when it does nor run straight or smoothly, and an anchor is foul when it is caught on an obstruction.

To fill with water and sink

A transverse structural member which gives the hull strength and shape. Wooden frames may be sawn, bent or laminated into shape. Planking is then fastened to the frames. A bent frame is called a timber.

The height of a ship's hull (excluding superstructure) above the waterline. The vertical distance from the current waterline to the lowest point on the highest continuous watertight deck. This usually varies from one part to another.

To roll or gather a sail against its mast or spar.


1. The spar that holds the upper edge of a four-sided fore-and-aft mounted sail.
2. A hook on a long pole to haul fish in.

Gaff rigged
A boat rigged with a four-sided fore-and-aft sail with its upper edge supported by a spar or gaff which extends aft from the mast.

Gaff vang
A line rigged to the end of a gaff and used to adjust a gaff sail's trim.

Gammon iron
The bow fitting which clamps the bowsprit to the stem.

The kitchen of the ship

A movable bridge used in boarding or leaving a ship at a pier; also known as a "brow".

An opening in the bulwark of the ship to allow passengers to board or leave the ship.

A large jib, strongly overlapping the mainmast.

To sail slowly when there is apparently no wind.

Give-way (vessel)
Where two vessels are approaching one another so as to involve a risk of collision, this is the vessel which is directed to keep out of the way of the other.

Global Positioning System (GPS)
A satellite based radionavigation system providing continuous worldwide coverage. It provides navigation, position, and timing information to air, marine, and land users.

Fitting that attaches the boom to the mast, allowing it to move freely.

Of a fore-and-aft rigged vessel sailing directly away from the wind, with the sails set on opposite sides of the vessel; for example with the mainsail to port and the jib to starboard, to maximize the amount of canvas exposed to the wind. Also see running.

When a ship (while afloat) touches the bed of the sea, or goes "aground" (qv).

Upper edge of the hull.


Half-breadth plan
An elevation (view) of the lines of a ship, viewed from above and divided lengthwise.

Originally, ropes used for hoisting a spar with a sail attached; today, a line used to raise the head of any sail.

Handy billy
A loose block and tackle with a hook or tail on each end, which can be used wherever it is needed. Usually made up of one single and one double block.

A fastener attached to the luff of the headsail that attaches the headsail to the forestay. Typical designs include a bronze or plastic hook with a spring-operated gate, or a strip of cloth webbing with a snap fastener.

A harbor is a place where ships may shelter from the weather or are stored. Harbours can be man-made or natural.

Hatchway, hatch
A covered opening in a ship's deck through which cargo can be loaded or access made to a lower deck; the cover to the opening is called a hatch.

Hauling wind
Pointing the ship towards the direction of the wind; generally not the fastest point of travel on a sailing vessel.

Hawse pipe, hawse-hole or hawse
The shaft or hole in the side of a vessel's bow through which the anchor chain passes.

Large rope used for mooring or towing a vessel.

The toilet of a vessel.

Any sail flown in front of the most forward mast.

A vessel's transient, vertical, up-and-down motion.

Heaving to
Stopping a sailing vessel by lashing the helm in opposition to the sails. The vessel will gradually drift to leeward, the speed of the drift depending on the vessel's design.

Heeling is the lean caused by the wind's force on the sails of a sailing vessel.

Location from which the vessel is steered

Highfield lever
A particular type of tensioning lever, usually for running backstays. Their use allows the leeward backstay to be completely slackened so that the boom can be let fully out.

A knot used to tie a rope or line to a fixed object. Also see bend.

When the peak of a wave is amidships, causing the hull to bend so the ends of the missing parameter for aname
are lower than the middle. The opposite of missing parameter for aname

The interior of a ship's hull, used as storage space, as for cargo.

1. Attachment of sheets to deck of vessel (main-sheet horse).
2. (v.) To move or adjust sail by brute hand force rather than using running rigging.

Attachments of stays to masts.

The shell and framework of the basic flotation-oriented part of a ship.

Of a vessel when only its upper parts are visible over the horizon.

Hull speed
The maximum efficient speed of a displacement-hulled vessel.

A boat with wing-like foils mounted on struts below the hull, lifting the hull entirely out of the water at speed and allowing water resistance to be greatly reduced.


Inboard motor
An engine mounted within the hull of a vessel, usually driving a fixed propeller by a shaft protruding through the stern. Generally used on larger vessels. Also see sterndrive and outboard motor.

In irons
When the bow of a sailboat is headed into the wind and the boat has stalled and is unable to maneuver

In-water survey
A method of surveying the underwater parts of a [ship]] while it is still afloat instead of having to [drydock]] it for examination of these areas as was conventionally done.


Jacklines or jack stays
Lines, often steel wire with a plastic jacket, from the bow to the stern on both port and starboard. The Jack Lines are used to clip on the safety harness to secure the crew to the vessel while giving them the freedom to walk on the deck.

Debris ejected from a ship that sinks or washes ashore. See also flotsam.

A triangular staysail at the front of a ship.

A spar used to extend the bowsprit.

To change from one tack to the other away from the wind, with the stern of the vessel turning through the wind. When ready to jibe the helmsman or skipper calls "Ready to jibe", the crew then each call "Ready!", and as the turn is made the helmsman calls "jibe oh!". A jibe may also happen accidentally when sailing downwind.


The central structural basis of the hull

Kitchen rudder
Hinged cowling around a fixed propeller, allowing the drive to be directed to the side or forwards to maneuver the vessel.

Connects two parts roughly at right angles, e.g. deck beams to frames.

The condition of a sailboat being pushed abruptly to horizontal, with the mast parallel to the water surface.

1. A unit of speed: {{Convert|1|nmi|km mi|sigfig=5}} per hour. Originally speed was measured by paying out a line from the stern of a moving boat. The line had a knot every {{Convert|47|ft|3|in|m}}, and the number of knots passed out in 30 seconds gave the speed through the water in nautical miles per hour.
2. A method of tying ropes


On board a ship, all "stairs" are called ladders, except for literal staircases aboard passenger ships. Most "stairs" on a ship are narrow and nearly vertical, hence the name.

A rope that ties something off.

Laying down
Beginning construction in a shipyard.

Small stowage locker at the aft end of a boat.

LED (Light Emitting Diode)
LEDs, as a type of diode, only conduct power and will light up only when the power is of the correct voltage polarity. The chief advantages of LEDs for marine navigation lights are the higher efficiency than incandescent lamps, which reduces energy consumption and have longer rated life times and are more resistant to vibration and impact than incandescent lamps.

The aft or trailing edge of a fore-and-aft sail; the leeward edge of a spinnaker; a vertical edge of a square sail. The leech is susceptible to twist, which is controlled by the boom vang, mainsheet and, if rigged with one, the gaff vang.

Lee side
The side of a ship sheltered from the wind.

The amount that a ship is blown leeward by the wind. See also weatherly.

In the direction that the wind is blowing towards.

Length overall, LOA
The length of a ship.

Lifebelt, lifejacket, life preserver
A device such as a buoyant ring or inflatable jacket which keeps a person afloat in the water.

Small boat kept on board a vessel and used to take crew and passengers to safety in the event of the ship being abandoned (usually an inflatable, covered raft) or used to rescue people from the water or from vessels in difficulty, usually.

The correct nautical term for the majority of the cordage or "ropes" used on a vessel. A line will always have a more specific name, such as sheet or halyard, which describes its use.

The vessel's angle of lean or tilt to one side, in the direction called roll. Typically refers to a lean caused by flooding or improperly loaded or shifted cargo (as opposed to 'heeling').

Long stay
A description for the relative slackness of an anchor chain; this term means taught and extended.

Loose footed
A mainsail that is not connected to a boom along its foot.

The forward edge of a sail.

Luff up
To steer a sailing vessel more towards the direction of the wind until the pressure is eased on the sheet.

1. When a sailing vessel is steered far enough to [windward and leeward|windward]] that the sail is no longer completely filled with wind (the [luff]] of a fore-and-aft sail begins to flap first).
2. Loosening a [sheet (sailing)|sheet]] so far past optimal trim that the sail is no longer completely filled with wind.
3. The flapping of the sail(s) which results from having no wind in the sail at all.

Lying ahull
Waiting out a storm by dousing all sails and simply letting the boat drift.


One of the braces attached to the mainmast.

Making way
When a vessel is moving under its own power.

The tallest mast on a ship.

Sail control line that allows the most obvious effect on mainsail trim. Primarily used to control the angle of the boom, and thereby the mainsail, this control can also increase or decrease downward tension on the boom while sailing upwind, significantly affecting sail shape. For more control over downward tension on the boom, use a boom vang.

A docking facility for small ships and yachts.

A vertical pole on a ship which supports sails or rigging.

A small platform partway up the mast, just above the height of the mast's main yard. A lookout is stationed here, and men who are working on the main yard will embark from here. See also Crow's Nest.

Mizzenmast (or Mizzen)
The third mast, or mast aft of the mainmast, on a ship.

Mizzen staysail
Sail on a ketch or yawl, usually lightweight, set from, and forward of, the mizzen mast while reaching in light to moderate air.

To attach a boat to a mooring buoy or post. Also, to a dock a ship.

A template of the shape of the hull in transverse section. Several moulds are used to form a temporary framework around which a hull is built.


Nautical mile
A distance of 1.852km. Approximately the distance of one minute of arc of latitude on the Earth's surface. A speed of one nautical mile per hour is called a knot.

Navigation rules
Rules of the road that provide guidance on how to avoid collision and also used to assign blame when a collision does occur.


Ocean Thermal Energy Conversion is a heat engine that uses the temperature difference that exists between deep waters and shallow waters. OTEC plants require a large diameter intake pipe, submerged at least a kilometer into the ocean's depths to bring very cold water to the surface.

A line used to control the shape of a sail.

To sail downwind directly at another ship, stealing the wind from its sails.

Hauling the buntline ropes over the sails to prevent them from chaffing.

The "ceiling," or, essentially, the bottom of the deck above you.

Capsized or foundered.


The pulsation in and out of the bow and stern plating as the ship alternately rises and plunges deep into the water

A method of lifting a roughly cylindrical object such as a spar. One end of a rope is made fast above the object, a loop of rope is lowered and passed around the object, which can be raised by hauling on the free end of rope.

A movable loop or collar, used to fasten a yard or gaff to its respective mast. Parrel still allows the spar to be raised or lowered and swivel around the mast. Can be made of wire or rope and fitted with beads to reduce friction.

Filling a seam (with caulking or pitch), lubricating the running rigging; paying with slush, protecting from the weather by covering with slush.

A long, thin triangular flag flown from the masthead of a military ship (as opposed to a burgee, the flags thus flown on yachts).

A vessel's motion, rotating about the beam/transverse axis, causing the fore and aft ends to rise and fall repetitively.

To capsize a boat end over end, rather than by rolling over.

When a fast-moving vessel skims over the water instead of pushing through it.

Another word for ama.

Poop deck
The deck on the aft superstructure of a ship.

Swamped by a high, following sea.

Towards the left-hand side of the ship facing forward (formerly Larboard). Denoted with a red light at night.

Porthole or port
An opening in a ship's side, esp. a round one for admitting light and air, fitted with thick glass and, often, a hinged metal cover, a window

Port tack
When sailing with the wind coming from the port side of the vessel. Must give way to boats on starboard tack.

A sail control line originating at some point on the boom leading to a fixed point on the boat's deck or rail (usually a cleat or pad eye) used to prevent or moderate the effects of an accidental jibe.

Propeller (prop) walk
Tendency for a propeller to push the stern sideways. In theory a right hand propeller in reverse will walk the stern to port.

A mechanical method of increasing force, such as a tackle or lever.


Refers to the dock or platform used to fasten a vessel to


A groove cut in wood to form part of a joint.

Acronym for RAdio Detection And Ranging. An electronic system designed to transmit radio signals and receive reflected images of those signals from a "target" in order to determine the bearing and distance to the "target".

Radar reflector
A special fixture fitted to a vessel or incorporated into the design of certain aids to navigation to enhance their ability to reflect radar energy. In general, these fixtures will materially improve the visibility for use by vessels with radar.

Range lights
Two lights associated to form a range (a line formed by the extension of a line connecting two charted points) which often, but not necessarily, indicates the channel centerline. The front range light is the lower of the two, and nearer to the mariner using the range. The rear light is higher and further from the mariner.

Sailing across the wind: from about 60° to about 160° off the wind. Reaching consists of "close reaching" (about 60° to 80°), "beam reaching" (about 90°) and "broad reaching" (about 120° to 160°). See also beating and running.

1. To temporarily reduce the area of a sail exposed to the wind, usually to guard against adverse effects of strong wind or to slow the vessel.
2. Rock or coral, possibly only revealed at low tide, shallow enough that the vessel will at least touch if not go aground.

Reef points
Small lengths of cord attached to a sail, used to secure the excess fabric after reefing.

Long pieces of rough canvas sewed across the sails to give them additional strength.

Ropes employed in the operation of reefing.

Relative bearing
A bearing relative to the direction of the ship: the clockwise angle between the ship's direction and an object. See also absolute bearing and bearing.

The system of masts and lines on ships and other sailing vessels.

Righting couple
The force which tends to restore a ship to equilibrium once a heel has altered the relationship between her center of buoyancy and her center of gravity.

The rim or 'eyebrow' above a port-hole or scuttle.

The anchor line, rope or cable connecting the anchor chain to the vessel. Also Anchor Rode.

A vessel's motion rotating from side to side, about the fore-aft/longitudinal axis. List (qv) is a lasting tilt in the roll direction.

A number of pulleys, engaged to confine the yard to the weather side of the mast; this tackle is much used in a rough sea.

The lines in the rigging.

Running rigging
Rigging used to manipulate sails, spars, etc. in order to control the movement of the ship. Cf. standing rigging.

Sailing more than about about 160° away from the wind. If directly away from the wind, it's a dead run.


When the trough of a wave is amidships, causing the hull to deflect so the ends of the [keel]] are higher than the middle. The opposite of hogging.

A set of drawings showing various sail combinations recommended for use in various situations.

Sampson post
A strong vertical post used to support a ship's windlass and the heel of a ship's bowsprit.

To reduce the area and efficiency of a sail by expedient means (slacking the peak and tricing up the tack) without properly reefing, thus slowing boat speed. Also used in the past as a sign of mourning.

1. A method of preparing an anchor for tripping by attaching an anchor cable to the crown and fixing to the ring by a light seizing (also known as becue). The seizing can be broken if the anchor becomes fouled.
2. A type of clinker dinghy, characteristically beamy and slow.

A name given by sailors to the lowest clouds, which are mostly observed in squally weather.

A term applied to a vessel when carried furiously along by a tempest.

Originally a series of pipes fitted through the ships side from inside the thicker deck waterway to the topside planking to drain water overboard, larger quantities drained through freeing ports, which were openings in the bulwarks.

A small opening, or lid thereof, in a ship's deck or hull.

A barrel with a hole in used to hold water that sailors would drink from. Also: [gossip]].

Cutting a hole in an object or vessel, especially in order to sink a vessel deliberately.

Sea anchor
A stabilizer deployed in the water for [heaving to]] in heavy weather. It acts as a brake and keeps the hull in line with the wind and perpendicular to waves. Often in the form of a large bag made of heavy canvas.

Sea chest
A watertight box built against the hull of the ship communicating with the sea through a grillage, to which valves and piping are attached to allow water in for ballast, engine cooling, and firefighting purposes.

A valve in the hull of a boat.

Certified for, and capable of, safely sailing at sea.

The upward curve of a vessel's longitudinal lines as viewed from the side.

Sheer plan
A diagram showing an elevation (view) of the ship's sheer viewed from the broadside.

A rope used to control the setting of a sail in relation to the direction of the wind.

Navigational instrument used to measure a ship's latitude.

Generally used to describe most medium or large vessels outfitted with smaller boats. As a consequence of this submarines may be larger than small ships, but are called boats because they do not carry boats of their own.

Shallow water that is a hazard to navigation.

Short stay
A description for the relative slackness of an anchor chain; this term means somewhat slack, but not vertical nor fully extended.

Standing rigging running from a mast to the sides of a ships.

A sound signal which uses electricity or compressed air to actuate either a disc or a cup shaped rotor.

A downward or sternward projection from the keel in front of the rudder. Protects the rudder from damage, and in bilge keelers may provide one "leg" of a tripod on which the boat stands when the tide is out.

The captain of a ship.

Slop chest
A ship's store of merchandise, such as clothing, tobacco, etc., maintained aboard merchant ships for sale to the crew.

Greasy substance obtained by boiling or scraping the fat from empty salted meat storage barrels, or the floating fat residue after boiling the crew's meal. Used for greasing parts of the running rigging of the ship.

Small bower (anchor)
The smaller of two anchors carried in the bow.

A method of using sound pulses to detect, range and sometime image underwater targets and obstacles, or the bed of the sea.

Measuring the depth of the water. Traditionally done by swinging the lead, now commonly by echo sounding.

A pole used to support various pieces of rigging and sails.

Finely-divided water swept from crest of waves by strong winds.

A large sail flown in front of the vessel while heading downwind.

Spinnaker pole
A spar used to help control a spinnaker or other headsail.

A line used parallel to that of the length of a craft, to prevent fore-aft motion of a boat, when moored or docked.

To join lines (ropes, cables etc.) by unravelling their ends and intertwining them to form a continuous line. To form an eye or a knot by splicing.

Spurling pipe
A pipe that connects to the chain locker, from which the anchor chain emerges onto the deck at the bow of a ship.

Squat effect
Phenomenon by which a vessel moving quickly through shallow water creates an area of lowered pressure under its keel that reduces the ship's buoyancy, particularly at the bow. The reduced buoyancy causes the ship to "squat" lower in the water than would ordinarily be expected, and thus its effective draught is increased.

A vertical post near a deck's edge that supports life-lines. A timber fitted in between the frame heads on a wooden hull or a bracket on a steel vessel, approx one meter high, to support the bulwark plank or plating and the [rail]].

Standing rigging
Rigging which is used to support masts and spars, and is not normally manipulated during normal operations. Cf. running rigging.

Stand-on (vessel)
A vessel [International Regulations for Preventing Collisions at Sea|directed]] to keep her course and speed where two vessels are approaching one another so as to involve a risk of collision.

Towards the right-hand side of a vessel facing forward. Denoted with a green light at night. Derived from the old steering oar or steerboard which preceded the invention of the rudder.

Starboard tack
When sailing with the wind coming from the starboard side of the vessel. Has right of way over boats on port tack.

Rigging running fore (forestay) and aft (backstay) from a mast to the hull.

A sail whose luff is attached to a forestay.

Steering flat
In a vessel, the compartment containing the steering gear.

The extension of keel at the forward end of a ship.

The rear part of a ship, technically defined as the area built up over the sternpost, extending upwards from the counter to the taffrail.

Stern tube
The tube under the hull to bear the tailshaft for propulsion (usually at stern).

A propeller drive system driven by an engine mounted within the hull. Unlike a fixed propeller (but like an outboard), the boat may be steered by twisting the drive. Also see inboard motor and outboard motor.

Stopper knot
A knot tied in the end of a rope, usually to stop it passing through a hole; most commonly a figure-eight knot.

A vessel's transient motion in a fore and aft direction.

A vessel's lateral motion from side to side.

To take up the last bit of slack on a line such as a halyard, anchor line or dockline by taking a single turn round a cleat and alternately heaving on the rope above and below the cleat while keeping the tension on the tail.


A large bracket attached firmly to the deck, to which the foot of the mast is fixed. It has two sides or cheeks and a bolt forming the pivot around which the mast is raised and lowered.

A leg of the route of a sailing vessel, particularly in relation to tacking and to starboard tack and port tack.

Zig-zagging so as to end up sail directly towards the wind (and for some rigs also away from it).

A kind of metallic shafting (a rod of metal) to hold the propeller and connected to the power engine. When the tailshaft is moved, the propeller may also be moved for propulsion.

Vertical wooden peg or pin inserted through the gunwale to form a fulcrum for oars when rowing. Used in place of a rowlock.

A bench seat across the width of an open boat.

A thin temporary patch.

a lever used for steering, attached to the top of the rudder post. Used mainly on smaller vessels, such as dinghies and rowing boats.

A low strip running around the edge of the deck like a low bulwark. It may be shortened or have gaps in it to allow water to flow off the deck.

The part of the hull between the waterline and the deck.

The operation of drawing a vessel forward by means of long lines.

Small fittings that slide on a rod or line. The most common use is for the inboard end of the mainsheet; a more esoteric form of traveller consists of "slight iron rings, encircling the backstays, which are used for hoisting the top-gallant yards, and confining them to the backstays".

A more or less flat surface across the stern of a vessel. Dinghies tend to have almost vertical transoms, whereas yachts’ transoms may be raked forward or aft.

Relationship of ship's hull to waterline.

A vessel with three hulls.

A knot passing behind or around an object.

The condition of a sailboat's (in particular a dinghy's) capsizing to a point where the mast is pointed straight down and the hull is on the surface resembling a turtle shell.


United Nations Convention on the Law of the Sea (external link) is the international agreement that defines the rights and responsibilities of nations in their use of the world's oceans, establishing guidelines for businesses, the environment, and the management of marine natural resources.

Under way
A vessel that is moving under control: that is, neither at anchor, made fast to the shore, aground nor adrift.

Underwater hull or underwater ship
The underwater section of a vessel beneath the waterline, normally not visible except when in drydock.

Slack off quickly and run slack to a belaying point. This order is given when a line or wire has been stopped off or falls have been four-in-hand and the hauling part is to be belayed.

A description for the relative slackness of an anchor chain; this term means that the anchor chain is slack and hangs vertically down from the hawse pipe.


The main (center) hull.

1. A rope leading from gaff to either side of the deck, used to prevent the gaff from sagging.
2. See boom vang.

Vanishing angle
The maximum degree of heel after which a vessel becomes unable to return to an upright position.

The shape of a boat or ship which the shape of the hull comes to a straight line to the keel.


Turbulence behind a vessel. Not to be confused with wash.

Central deck of a ship

A number of strong and thick planks running length-wise along the ship, covering the lower part of the ship's side.

The waves created by a vessel. Not to be confused with wake.

Water transport vessels. [Ship]]s, [boat]]s, [personal water craft]] etc.

1. A navigable body of water.
2. A strake of timber laid against the frames or bulwark stanchions at the margin of a laid wooden deck, usually about twice the thickness of the deck planking.

A wave, in general, is a disturbance that propagates through space and time. Ocean waves are mechanical surface waves. See Wave.

Weather gauge
Favorable position over another sailing vessel with respect to the wind.

Weather deck
Whichever deck is that exposed to the weather.

Weather side
The side of a ship exposed to the wind.

A ship that is easily sailed and maneuvered; makes little leeway when sailing to windward.

Weigh anchor
To heave up (an anchor) preparatory to sailing.

Place in the ship's hold for pumps.

White horses or whitecaps
Foam or spray on wave tops caused by stronger winds (usually above Beaufort scale 4).

The usual steering device on larger vessels: a wheel with a horizontal axis, connected by cables to the rudder.

Location on a ship where the wheel is located; also called pilothouse or bridge.

Wide berth
To leave room between two ships moored (berthed) to allow space for maneuver.

Wind resistance of the boat.

In the direction that the wind is coming from. Opposite of Leeward

A winch mechanism, usually with a horizontal axis. Used where mechanical advantage greater than that obtainable by block and tackle was needed (such as raising the anchor on small ships).


A hexagonal plan watercraft conforming to standards of seaworthiness and modularity.


The horizontal spar from which a square sail is suspended.

The very end of a yard. Often mistaken for a "yard", which refers to the entire spar.

A vessel's rotational motion about the vertical axis, causing the fore and aft ends to swing from side to side repetitively.


A light (westerly) wind.

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