Quick Summary
This comprehensive glossary introduces more than 150 essential nautical terms used at sea. It serves as a foundational reference for new seafarers learning the language of ships, navigation, seamanship, and life onboard.
Introduction
Every world has its language, and the sea is no different. When you step aboard a vessel for the first time, you hear terms that may feel foreign, even though they’ve been spoken by mariners for centuries. Some describe the parts of a ship, others explain movements of wind and sea, and many exist for one purpose alone: to keep communication clear when safety depends on precision.
This glossary gathers the essential nautical words every new seafarer must know. Learn them well, and the ship will begin to make sense — its orders, its routines, and its unspoken rules.
Terms Related to Ship Structure
Bow
The forward end of a ship. The part that cuts through the water.
Stern
The aft end of the ship. The opposite of the bow.
Port
The left side of the vessel when facing forward.
Starboard
The right side of the vessel when facing forward.
Hull
The main body of the ship, including the framework and outer shell.
Deck
A horizontal platform on a ship, similar to a floor.
Bridge
The control center of the ship, where navigation and watchkeeping occur.
Forecastle (Foc’sle)
The forward part of the ship, often housing equipment and crew spaces.
Superstructure
The part of the ship built above the main deck.
Bulkhead
A vertical wall inside a ship, creating compartments for strength and safety.
Deckhead
The ceiling of a compartment.
Hold
An enclosed space used for cargo storage.
Freeboard
The height of the ship’s side from the waterline to the main deck.
Beam
The widest part of the vessel.
Draft
How deep the ship sits in the water, measured from keel to waterline.
Keel
The structural backbone of the ship, running along the bottom.
Ballast
Water or weight carried to improve stability and trim.
Bulwark
The solid wall along the edge of a deck.
Scupper
A deck drain that allows water to escape overboard.
Companionway
A stair or ladder leading from one deck to another.
Galley
The ship’s kitchen.
Mess
The dining area for crew or officers.
Cabin
A crew member’s sleeping quarters.
Terms Related to Ship Operations
Mooring
Securing the ship to a berth using lines.
Berth
A place where the ship is docked or anchored.
Anchoring
Lowering the ship’s anchor to hold position.
Dropping Anchor
Letting the anchor fall and set on the seabed.
Heaving Up
Raising the anchor.
Windlass
Machinery used to raise or lower the anchor.
Capstan
A rotating machine used to handle ropes and lines.
Fairlead
A fitting that guides lines to prevent chafing.
Bollard
A strong post on deck or ashore for securing lines.
Fender
A cushion placed between ship and dock to prevent damage.
Gangway
A walkway used for boarding or leaving the ship.
Muster
A gathering of crew for drills or roll call.
Muster List
A list showing duties assigned during emergencies.
Watch
A scheduled duty period for navigation, engine work, or patrol.
Helmsman
The seafarer steering the vessel.
Pilothouse
The enclosed space where the ship is steered.
Navigation Terms
Nautical Mile
A distance unit equal to one minute of latitude (1.852 km).
Knot
A unit of speed equal to one nautical mile per hour.
Course
The intended direction of travel.
Heading
The direction the ship is currently pointing.
Bearing
The direction to an object from the observer’s position.
Fix
A known ship position determined by navigation methods.
Dead Reckoning
Estimating the ship’s position based on course and speed.
Waypoint
A designated navigation point in a passage plan.
Chart
A nautical map showing depths, hazards, and aids to navigation.
ECDIS
Electronic Chart Display and Information System.
Radar
Equipment that detects objects and landmasses by radio waves.
AIS
Automatic Identification System; transmits vessel information.
Latitude
Distance north or south of the equator.
Longitude
Distance east or west of the prime meridian.
TSS (Traffic Separation Scheme)
Designated lanes that organize vessel traffic.
Pilotage
Navigating in restricted waters with local assistance.
Buoys, Lights, and Aids to Navigation
Lateral Marks
Buoys marking channel edges.
Cardinal Marks
Buoys indicating where safe water lies relative to a hazard.
Isolated Danger Mark
Indicates a specific nearby hazard.
Safe Water Mark
Shows that safe water exists in all directions.
Special Mark
Marks areas with specific regulations.
Light Characteristics
Rhythms and flashes used to identify aids to navigation.
Range Lights
Pairs of lights used for lining up a safe course.
Beacon
A fixed navigation aid on land or in shallow water.
Meteorology and Sea State
Beaufort Scale
Measures wind force.
Swell
Waves generated by distant weather systems.
Fetch
The distance wind travels over water to create waves.
True Wind
Wind felt relative to the earth.
Apparent Wind
Wind felt from the moving ship.
Tide
The rise and fall of sea level due to gravitational forces.
Flood Tide
Incoming tide.
Ebb Tide
Outgoing tide.
Slack Water
Period with minimal tidal movement.
Safety and Emergency Terms
Abandon Ship
Order given to leave the vessel.
Lifeboat
A boat used for emergency evacuation.
Liferaft
Inflatable survival craft.
EPIRB
Emergency Position-Indicating Radio Beacon.
SART
Search and Rescue Transponder.
Muster Station
Place where crew assemble during emergencies.
Fire Triangle
Heat, fuel, oxygen — elements required for fire.
Fire Plan
A diagram showing fire equipment and escape routes.
SCBA
Self-Contained Breathing Apparatus.
Hydraulic Lock
Dangerous pressure buildup in machinery or hoses.
Engine Room and Machinery Terms
Main Engine
The vessel’s primary propulsion engine.
Generator
Produces electrical power.
Bilge
The lowest interior part where water collects.
Bilge Pump
Removes accumulated water.
Shaft
Connects the engine to the propeller.
Rudder
Controls ship direction when underway.
Steering Gear
Machinery that moves the rudder.
Manifold
System for controlling cargo flow on tankers.
Separator
Machine that removes water from fuel or oil.
Sounding
Measuring tank levels with a weighted tape.
Cargo Terms
TEU
Twenty-foot Equivalent Unit; container measurement.
Bulk Cargo
Unpackaged cargo like grain or ore.
Breakbulk
Cargo in individual units such as bags, crates, or barrels.
Reefer
A refrigerated container.
Hatch Cover
Covering for cargo hold openings.
Tank
Enclosed space for liquid cargo.
Ullage
Empty space above liquid cargo in a tank.
Trim
Balance of cargo fore and aft.
Commands and Orders
Hard to Port / Hard to Starboard
Strong rudder commands.
Midships
Rudder centered.
Stand By
Prepare for maneuver or operation.
Let Go
Release a line or anchor.
Heave In
Pull in a line.
Belay
Stop an action immediately.
General Seafaring Terms
Seaworthy
Fit and safe for a sea voyage.
Sounding Line
A traditional tool for measuring depth.
Lee Side
The side sheltered from the wind.
Windward
The side facing the wind.
Beam Sea
Waves coming from the side.
Following Sea
Waves moving in the same direction as the ship.
Pitch
Up-and-down motion of the bow and stern.
Roll
Side-to-side motion.
Yaw
Swinging of the bow from side to side.
Ground Tackle
Equipment used for anchoring.
Flare
Wider shape of the ship’s bow for deflecting spray.
Conclusion
These terms form the language of the sea — the shared vocabulary that keeps communication clear and operations safe on every vessel, from small harbor tugs to deep-sea tankers. Learn them well, practice them daily, and you will soon move through the ship with confidence and understanding.
Fair winds as you continue mastering the language of the mariner.
