1 fathom

6 feet

1 horsepower

15 pounds of thrust

1 meter

3.1 feet

1 nautical mile

1.15 statute mile

1 nautical mile

1 minute latitude (1/60 of a degree)

1 nautical mile

6,072 feet

1 nautical mile

2,024 yards

1 nautical mile

1,850.7 meters

1 statute mile

5,280 feet

1 statute mile

1,760 yards

1/6th nautical mile

1 second of latitude

60 nautical miles

1° (degree) latitude

Abeam

Off the side of (at right angle to) the boat.

Aft

At or toward the stern of behind the boat.

Alternator

A device which generates electricity from an engine.

Amidships

Toward the center of the boat.

Apparent wind

The wind aboard a moving boat.

ARA

Armada of the Republic of Argentine (Argentina)

Astern

Behind the stern of the boat.

Athwartships

Across the boat from side to side.

Average speed

5 – 6 knots for most large keel boats

Back

To hold the clew of a sail out to windward.  A counterclockwise change in wind direction.

Back & fill

Using forward and reverse gears, as well as prop walk and rudder angles, to turn a boat in close quarters.

Backing wind

Wind shift to the left

Backstay

The standing rigging running from the stern to the top of the mast.

Ballast

Weight in the keel that provides stability.

Ballast ratio (should be at least 40%)

Weight of ballast divided by gross weight of the boat

Barometer

A weather forecasting instrument that measures air pressure.

Batten

A thin slat that slides into a pocket in the leech of a sail, helping it hold its shape.

Battery starting power

100% at 80°, 65% at 32°, 40% at 0°

Battery switch

The main electrical cutoff switch.

Beam

The width of a boat at its widest point.

Beam reach

Sailing in a direction at approximately 90 degrees to the wind.

Bear away

To fall off, head away from the wind

Bearing

A course sailed upwind.

Below

The area of a boat beneath the deck.

Bend

To attach a sail to a spar or a headstay, or to attach a line to a sail.

Berth

The area in which you park your boat.  The area in which you sleep on a boat.

Bight

A loop in a line.

Bilge

The lowest part of the boat's interior where water on board will collect.

Bimini

 A sum awning used to cover the cockpit area.

Bitter end

The end of a line.

Black Squall

Dark and threatening.  Usually accompanied by rain.

Blanket

To use a sail or object to block the wind from filling a sail.

Block

A pulley on a boat.

Boat hook

A pole with a hook used for grabbing hold of a mooring or an object in the water.

Bolt rope

The rope sewn into the foot and luff of some mainsails and jibs by which they are attached to the boat.

Boom vang

A block and tackle system which pulls the boom down to assist sail control.

Bottom Paint Components

Toxicant, Vehicle or binder, Thinners, & Pigment

Bow

The forward part of the boat.

Bow line

A line running from the bow of the boat to the dock or mooring.

Bowline

A knot designed to make a loop that will not slip and can be easily untied.

Breast line

A short dock line leading off the beam of the boat directly to a dock.

Broach 

An uncontrolled rounding, usually from a downwind point of sail.

Broad reach

Sailing in a direction with the wind at the rear corner of the boat (approximately 135 degrees from the bow).

Bulkhead

A wall that runs athwartships on a boat.

By the lee

Sailing on a run with the wind coming over the same side of the boat as the boom.

Cabin

The interior of a boat.

Can

An odd-numbered, green buoy.

Capacity

(Boat length x boat width) divided by 15

Careening

Running a boat onto a sloping shore at high tide to expose the bottom for maintenance at low tide.

Cast-off

To release a line.

Chainplate

Strong metal plate which connect the shrouds to the boat.

Channel

A path in the water marked by buoys in which the water is deep enough to sail.

Chart

A nautical map.

Charter

To rent a boat.

Chock

A guide mounted on the deck through which docklines and anchor rodes run.

Chop

Rough, short, steep waves.

Clew

The lower, aft corner of a sail.

Close reach

Sailing in a direction with the wind forward of the beam but aft of the closed-hauled position.

Close-hauled

The point of sail closest to the wind.

Cockpit

The lower area in which the steering controls and sail controls are located.

Coil

To neatly loop a line for storage.

Come about

See "tack."

Companionway

The steps leading from the cockpit to the cabin below.

Compass protractor

A plotting instrument oriented to latitude-longitude lines.

Compass rose

The circle on a chart which indicates the direction of true north and magnetic north.

Converter

A device to change AC current to DC.

Cringle

A ring sewn into the sail through which a line can be passed.

Current

The horizontal movement of water caused by tides, wind, and other forces.

Dinghy

A small sailboat, rowboat, or small boat with an outboard.

Displacement

Weight of a boat (i.e. the amount of water it displaces).

Distance to a storm (nautical miles)

(# of seconds between lightning & thunder) / 5.5

Distance to a storm (statue miles)

(# of seconds between lightning & thunder) / 5

Divider

Instrument used for measuring distances or coordinates on a chart.

Dock

Wooden structure where a boat can be tied up.  The act of bringing a boat along side a structure.

Docking

Floating a vessel into dry-dock and pumping out the water to expose the bottom for maintenance.

Dockline

A line used to secure the boat to the dock.

Downwind

A direction away from the direction of the wind.

Draft

The depth of a boat below the water's surface

Ebb

An outgoing tide

EPIRB

An emergency position indicating radio beacon.

Fathom

A measurement of depth of the water.  One fathom equals six feet.

Fender

A rubber bumper used to protect a boat.

FGS

Federal German Ship (Germany)

Fitting

A piece of natural hardware.

Float plan

An itinerary of your intended sailing trip left with a responsible party onshore.

Float switch

A device that turns on a bilge pump when water inside reaches a certain level.

Flood

Incoming tide.

Flotilla

A group of boats on an organized cruise.

Foot

Bottom edge of a sail.

Fore

Foreword

Foresail

A jib or a genoa.

Forestay

The standing rigging running from the bow to the mast to which the jib is attached.

Forward

Toward the bow.

Fouled

Tangled.

Furl

To fold or roll up a sail.

FV

Fishing Vessel (non-military merchant ship)

Genoa

A large jib whose clew extends aft of the mast.

Gimbal

A system that keeps items horizontal as the boat heels.

Grommet

A reinforcing metal ring in a sail.

Ground tackle

The anchor and rode (chain and line).

Gunwale

The edge of the deck where it meets the topsides.

Halyard

A line used to hoist or lower a sail.

Hank

A snap hook that attaches the luff of a jib to the forestay.

Hard over

To turn the tiller or wheel as far as possible in one direction.

Hard-a-lee

Command given to the crew to begin a tack.

Hatch

A large covered opening on a boat.

Haul in

To tighten a line.

Hauling

Maneuvering a boat into a wheeled cradle running on an underwater railway and winching her ashore for maintenance.

Head

The top corner of a sail.  The bathroom on a boat.  The toilet on a boat.

Heading

The direction of the boat expressed in compass degrees.

Heave-to

To hold a position in the water in which the force of the wind and the rudder counter one another.

Heaving Down

Attaching tackles to the masthead and heaving a boat onto its side to expose the bottom for maintenance.

HMAS

Her Majesty’s Australian Ship (Australia)

HMCS

Her Majesty’s Canadian Ship (Canada)

HMNZS

Her Majesty’s New Zealand Ship (New Zealand)

HMS

Her Majesty’s Ship (UK & Saudi Arabia)

Holding ground

The bottom ground in an anchorage used to hold the anchor.

Holding tank

A tank that holds and stores human waste rather than pumping it overboard.

Hove-to

A boat that has successfully completed the process of heaving-to and is holding its position.

Hull speed

Theoretical maximum speed of a sailboat determined by the length of its waterline.

In irons

A boat that is head-to-wind, making no forward headway.

INS

Indian Naval Ship (India) & Israeli Naval Ship (Israel)

Inverter

A device to change DC current to AC.

Isobar

A line joining places of equal air pressure as depicted on a weather map.

Jacklines

Study lines affixed to the sides of the boat to which the crew and attach their safety harnesses.

Jib

The small forward sail attached to the forestay.

Jibe

To change direction of a boat by steering the stern through the wind.

Jury rig

An improvised, temporary repair.

Land breeze

A wind blowing over land and out to sea.

Lash

To tie down.

Lay

To sail a course that will clear an obstacle without tacking.

Lazarette

A storage compartment built into the deck.

Lead

To pass a line through a fitting or block.

Lee helm

The boat's tendency to turn away from the wind.

Lee shore

Land which is on the leeward side of the boat.

Leech

The after edge of a sail.

Leeward

The direction away form the wind (where the wind is blowing to).

Leeward side

Side of the boat or said that is away from the wind.

Leeway

5° – 10° for most large keel boats

Leeway

Sideways slippage of a boat in a direction away from the wind.

Line

A nautical rope.

Luff

The forward edge of a sail. The fluttering of a sail caused by aiming too close to the wind.

Magnetic

In reference to magnetic north rather than true north.

Mast step

The structure at the bottom of the mast.

Masthead

Top of the mast.

Masthead fly

A wind direction indicator at the top of the mast.

Maximum speed

1.34 x square root of the length of the waterline

Mayday

The internationally recognized distress signal for a life-threatening emergency.

Moonrise

40 minutes later than the previous night

Mooring

A permanently anchored ball or buoy to which a boat can be tied.

MS

Motor Ship (non-military merchant ship)

MSD

Marine sanitation device - includes toilet, holding tank and connecting lines and valves.

Nautical mile

A distance of 6076 feet, equaling one minute of the earth's latitude.

Navigation rules

Laws established to prevent collisions on the water.

Net tonnage

Gross tonnage--the total internal volume--minus all spaces not available for carrying passengers and cargo

No-go zone

Area in the wind where a boat cannot produce power to sail.

Nun

A red, even numbered buoy.  Nuns are usually paired with cans.

Offshore

Away from or out of sight of land.

Offshore wind

Wind blowing away from the land.

Outboard

A portable motor mounted on the transom.

Outhaul

The controlling line attached to the clew of a mainsail used to tension the foot of the sail.

Overpowered

A boat that is heeling too far because it has too much sail for wind conditions.

Overtaking

A boat that is catching up to another boat and about to pass it.

Painter

The line attached to the bow of a dinghy.

Pan-pan

The internationally recognized distress signal for an urgent but not life threatening situation.

Parallel rulers

Two rulers linked and held parallel by hinges used to plot a course.

Pay out

To ease out a line.

PFD

Abbreviation for personal floatation device (i.e. a life jacket).

Piling

A vertical timber or log driven into the sea bottom to support docks or form a breakwater.

Plot

Apply calculations to chart a position or course.

Point

To steer close to the wind.

Points of sail

Boat directions in relation to the wind.

Port

Left side of a vessel facing forward.  (Adopted by general order in 1846 by US Navy rather than “larboard” which could be confused with “starboard.”)

Port

The left side of a boat when facing forward.  A harbor.  A window in a cabin on a boat.

Port tack

Sailing on any point of sail with the main boom on the starboard side of the boat.

Prevailing wind

Typical or consistent wind conditions.

Propane

A cooking fuel.

Pulpit

The stainless steel guardrail at the bow and stern of some boats.

Quarter

Sides of the boat near the stern.

Quarter berth

A bunk located under the cockpit.

Radar reflector

An object with lots of faces at sharp angles that can be spotted by other vessels radar scopes.

Rake

The angle of the mast.

Range

The alignment of two objects that indicates the middle of a channel.

Raw water

The fresh or salt water entering the boat.

Reach

One of several point of sail across the wind.

Reef

To reduce the size of a sail.

Reefing line

A line used to reduce sail by pulling the lower portion of the sail to the boom.

Rhumb line

A straight course between two points.

Rig

The design of a boat's mast, standing rigging, and sail plan.  To prepare a boat for sailing.

Rigging

The wires and lines used to support and control the sails.

Right-of-way

The right of the stand-on vessel to hold its course.

Rode

Line and chain attached from the boat to the anchor.

Roller furling

A mechanical system to roll up a headsail (jib) around the headstay.

Round up

When a boat turns toward the wind, sometimes abruptly and with a great deal of heel.

Rudder

The underwater fin controlled by the wheel or tiller that deflects water and steers the boat.

Run

Sailing with the wind coming from behind the boat.

Running rigging

Line and hardware used to control the sails.

Sail ties

Pieces of line or webbing used to tie the mainsail to the boom when reefing or storing the sail.

Scope

The ratio of the amount of anchor rode deployed to the distance from the bow of the boat to the bottom.

Scull

To propel the boat by swinging the rudder back and forth like a fish tail.

Scupper

Cockpit or deck drain.

Sea breeze

A wind that blows over the sea and onto the land.

Seacock

A valve which opens and closes a hole through the hull of a boat.

Secure

Make safe or cleat.

Securite

An internationally recognized signal to warn others of a dangerous situation.

Set

The direction of a current.  To trim the sails.

Shackle

A metal fitting at the end of a line used to attach the line to a sail or other fitting.

Shake out

To remove a reef and restore the full sail.

Sheave

A rotating wheel inside a block or fitting.

Sheet

The line which is used to control the sail by easing it out or trimming it in.

Shoal

Shallow water that may be dangerous.

Shroud

Standing rigging at the side of the mast.

Skeg

A vertical fin in front of the rudder.

Skipper

The person in charge of the boat.

Slab reefing (jiffy reefing)

Lowering and tying off the lower portion of a sail in order to reduce sail area.

Slip

See "berth."

Snub

To hold a line under tension by wrapping it on a winch or cleat.

Sole

The floor in a cockpit or cabin.

Solenoid switch

An electrical switch which shuts off the flow of propane.

Spar

A pole used to attach a sail on a boat (e.g. mast, boom, gaff).

Spinnaker

A larger billowing headsail used when sailing downwind.

Splice

Joining tow lines together by interweaving their stands.

Spreader

A support strut extending athwartships from the mast used to support the mast and guide the shrouds to the chainplates.

Spring line

A dockline running forward or aft from the boat to the dock to keep the boat from moving forward or aft.

Squall

Sudden, violent gust of wind

Squall

A short, intense storm with little warning.

SS

Steam Ship (non-military merchant ship)

Stanchions

Stainless steel supports a the edge of the deck which hold the lifelines.

Standing rigging

The permanent rigging (usually wire) of a boat that includes the forestay, backstay, and shrouds.

Stand-on vessel

Vessel or boat with the right-of-way.

Starboard

Right side of a vessel facing forward.

Starboard

The right side of the boat facing forward.

Starboard tack

Sailing on any point of sail with the main boom on the port side of the boat.

Stay

A wire support for a mast, part of the standing rigging.

Staysail

A second small "inner jib" attached between the bow and the mast of a cutter.

Steerage or Steeageway

The minimums amount of speed needed to control direction of the vessel.

Stem

The forward tip of the bow.

Stern

The aft part of the boat.

Stuffing box

The opening in the hull where the propeller shaft exits.

Sump

A cavity or tank in the bilge to collect water.

Tack

A course on which the wind comes over one side of the boat (e.g. port tack).  To change direction by turning the bow through the wind.  The lower forward corner of a sail.

Tackle

A sequence of blocks and line that provides a mechanical advantage.

Tail

To hold and pull a line from behind a winch.

Telltales

Pieces of yarn or sailcloth attached to sails that indicate when the sail is properly trimmed.

Tether

A length of line connecting safety harness to padeye or jackline.

Throttle

A device for controlling the engine's revolutions per minute (RPM).

Tide

The rise and fall of water level due to the gravitational pull of the sun and moon.

Toe rail

A short aluminum or wooden rail around the outer edges of the deck.

Topping lift

A line used to hold the boom up when the mainsail is lowered or stowed.

Topsides

The side of the boat between the water line and the deck.

Transom

The vertical surface of the stern.

Traveler

A track or bridle that controls sideways movement of the mainsail.

Trim

To pull on a sheet.  How a sail is set relative to the wind.

True wind

The actual speed and direction of the wind when standing still.

Tune

To adjust a boat's standing rigging.

Turnbuckle

A mechanical fitting attached to the lower ends of stays used to adjust the standing rigging.

Underway

To be moving under sail or engine.

Upwind

Toward the direction of the wind.

USCGC

U.S. Coast Guard Cutter

USNS

United States Naval Ship (Military Sealift Command)

USS

United States Ship “in service”

V-berth

A bunk in the bow of the boat that narrows as it goes forward.

Veer

A clockwise change of wind direction.

Veering wind

Wind shift to the right

Vessel

Any sailboat, powerboat, or ship.

VHF

Abbreviation for very high frequency, a two-way radio commonly used in boating.

Wake

Waves caused by a boat moving through the water.

Waterline

The horizontal line on the hull of a boat where the water surface should be.

Weather helm

The boat's tendency to head up toward the wind.  Occurs when a sailboat  is overpowered or the sail trim is out of balance (jib trim too loose and/or mainsail trim too tight.

Weather side

Same as "windward side."

Whip

To bind together the stands at the end of a line.

Whisker pole

A temporary pole used to hold the jib out and keep it full when sailing downwind.

White Squall

Squall announced only by whitecaps, a whitish haze in the air, and a rushing sound.

Winch

A drum with a handle offering mechanical advantage used to trim sheets or raise sails.

Windage

The amount of surface area on a boat that is presented to the wind.

Windlass

A mechanical device, usually electric, secured to the bow of the boat or in the anchor locker that is used to raise and lower the anchor.

Windward

Toward the wind.

Windward side

The side of a boat or sail closest to the wind.

Wing-and-wing

Sailing downwind with the jib set on the opposite side of the mainsail.

Working sails

The mainsail and standard jib.

Working sheet.

The leeward jib sheet that is tensioned by the wind on the sail.

Y-valve

A double valve used to redirect water flow.