An Agency Fee is a sum of money that is charged to the vessel by the ship's agent to compensate for any services that were received while the ship was in port.

If a vessel is Adrift she is floating without being either steered or moored.

When a vessel is in transit the water that is moving around the hull creates a hydrodynamic force. Because a ship is a complexly shaped object as opposed to a simple tube or sphere for example an additional quantity of water is added to the water which has been displaced by the vessel’s movement to factor in the Added Mass.

Aweigh is a term used to describe the moment when the anchor has just been lifted from the seabed.

The Afterbody is the section of a vessel's hull which lies aft of midships. It encompasses the entire after half of the hull from the upper deck to the keel.

The Aft Peak Tank is a water tank that is located in the right aft of a vessel. The tank will either be a designated freshwater tank or a ballast water tank which will be used to adjust the ship’s trim.

Admeasurement is the formal measurement of a vessel in order to determine its capacity or tonnage.

The Accommodation Ladder is a portable flight of stairs with handrails that is attached to the side of a vessel. This enables easy access between the dock or a smaller boat and the ship. The ladder is designed so that no matter what its angle of inclination the steps will always be horizontal.

An Aids to Navigation Service Vessel is a ship or boat that carries special equipment in order to service maintain and repair navigation aids such as automatic lighthouses buoys beacons and lights.

Aground is the word used when a vessel is lying upon or touching shallow ground. The opposite of being afloat.

An Alleyway is the name given to any corridor onboard a vessel that connects one area of the accommodation to another.

The Aft Peak Bulkhead is the name for the first main transverse bulkhead forward of the stern. It must be kept watertight.

Abandon Ship is a phrase used to inform the passengers and crew that they need to leave the ship immediately due to an emergency such as the vessel being about to sink.

An Able Bodied Seaman (also called an Able Seaman or just AB) is a member of the Deck Department. They will have more than two years’ worth of experience and be expected to know the ins and outs of their job. An Able Seaman’s duties and responsibilities include standing watch / keeping lookout cleaning and maintenance conducting security rounds supervising lower ranking deck crew and assisting with operations such as docking undocking line handling and the loading and unloading of cargo.  

The Accommodation area is the part of the ship in which the crew facilities are located. This includes the cabins and the crew mess (the dining area and place where crew members can hang out when they aren’t working.)

Active Fin Stabilizers aim to reduce the rolling of a vessel in rough seas. This helps to provide greater stability and safety while reducing the negative impact on speed and fuel performance in adverse conditions. The fins are normally located near amidships on both sides (port and starboard) of the ship. They can be both retractable and non-retractable. Active Fin Stabilizers have long been a feature of passenger ships such as cruise liners however they are becoming increasingly popular on commercial cargo and container ships.   

Usually described as 'force majeure' particularly in documents pertaining to Insurance an Act of God is a natural event that is unpredictable and not able to be prevented by humans. Acts of God include floods lightning storms tsunamis etc. 

ACV stands for Air Cushion Vehicle - otherwise known as a hovercraft is supported mainly or in its entirety by a cushion of air. ACVs are supported both when in motion and at rest meaning the air must be continuously generated.

Administration in shipping refers to the government of the state under whose authority a vessel is operating. A ship flies a flag of a State and the Administration is therefore the government of that state.

If a vessel is Afloat she is in the state of floating on water. She is not in dry dock on land or run aground.

 An Aframax tanker is an oil tanker that has a DWT (deadweight) of between 80000 and 120000 metric tonnes. The name Aframax comes from Average Freight Rate Assessment (AFRA) - a rating system used for tankers coined by Shell Oil in 1954 in order to standardize the terms of shipping contracts. Because of their size Aframax tankers are best suited to short- to medium-haul journeys however their size is also to their advantage as they are able to serve the majority of the world’s ports particularly those in regions that are unable to accommodate VLCC (very large crude carriers) and ULCC (ultra large crude carriers) tankers due to their smaller ports or lack of offshore oil terminals.   

The A-frame is a lifting apparatus commonly found installed on the stern of pipe laying vessels cable laying vessels and offshore construction vessels.

Aft means towards or near to the vessel's stern.

The Afternoon Watch is the period of being on duty (AKA Watch) that takes place onboard a vessel between 1200hrs and 1600hrs.

The Aft Peak is a compartment that is located aft (at near or towards the vessel’s stern) of the aftermost watertight bulkhead. 

The Aft Perpendicular on a ship is an imaginary vertical line which is drawn between the forward side of the stern with the summer load waterline. However it depends on the designer of the ship whether the Aft Perpendicular is drawn through the aft side of the rudder post or through the center-line of the rudder pintles. The Length Overall (LOA) is the distance between the fore and aft extreme points of the vessel and is the aft reference line for hydrostatic calculations.

Aids to Navigation (AtoN) are anything that helps a vessel navigate more safely. They are charted marks and include items such as beacons lighthouses buoys lights and radio beacons.

An Air Cushion Vehicle (ACV) otherwise known as a hovercraft is supported mainly or in its entirety by a cushion of air. ACVs are supported both when in motion and at rest meaning the air must be continuously generated.

The Air Draft (or Air Draught) is the vertical distance from the surface of the water (the waterline) to the highest fixed point on a vessel.

An Air Lock is a protected enclosed area generally found on a gas carrier vessel that enables safe entrance between a dangerous gas zone and a gas safe space.

Air Lubrication is a way to reduce hull friction by generating a layer of air between the underside of a vessel and the surface of the water. This increases a ship’s efficiency by reducing drag by up to 15%.

Air Resistance refers to a vessel’s resistance to motion that is caused by the air circulating around the part of the ship that is above water.

Air Trunks are a part of a vessel’s hull that either contain air ducts as well as other lines such as pipes and cables or are themselves used to conduct air.

AIS stands for Automatic Identification System - an automated tracking system that is used to identify vessels assist in target tracking simplify information exchange and provide additional information to boost situational awareness.

The Aldis Lamp (also called a Signal Lamp or Morse Lamp) is a hand-held electric lamp which is normally found on the bridge wing of a vessel. It is used to signal Morse code messages via flashing light between ships of all types including naval and commercial.

All Hands refers to the entire ship’s company including all crew members as well as officers. Most commonly heard in the expression "All Hands on Deck.”

Allision is the name given to the act of a moving ship striking or colliding with a stationary object - such as a dock. Not to be confused with collision which generally refers to two vessels colliding with one another.

A vessel is Alongside when she is positioned side by side with another ship or a jetty wharf or dock.

Amidships refers to the middle of a ship either longitudinally or laterally. In ship building amidships is located in the middle of the length of the vessel.

An Anchor is a heavy object or device that is attached to a cable chain or rope and is shaped typically with barbed flukes so that it grips the sea bed. The Anchor holds a ship (or other floating structure) in her desired position regardless of wind and current.

Anchorage is the fee charged by a port or harbor to allow a vessel to moor there.

The Anchor Ball is a round black ball which is displayed at the front of a vessel to show that the ship is anchored.

The Anchor Buoy is a small buoy that is sometimes used to mark the position of the anchor when it's on the bottom. The Anchor Buoy is fastened to the anchor's crown by a buoy rope and normally either painted red (port) or green (starboard).

The Anchor Cable (or Anchor Rode Anchor Chain or Anchor Rope) is attached at one end to the vessel and at the other end to the anchor. 

The Anchor Chain (or Anchor Rode Anchor Cable or Anchor Rope) is attached at one end to the vessel and at the other end to the anchor. 

An Anchor Handling Tug is a type of Tugboat that is used to move anchors as well as for towing drilling vessels lighters and other similar vessels.

Anchor Lights are the lights that a vessel must display when she is at anchor.

The Anchor Pocket is a recess in the bow of a ship that houses a stockless anchor.

The Anchor Rode (or Anchor Chain Anchor Cable or Anchor Rope) is attached at one end to the vessel and at the other end to the anchor. 

The Anchor Rope (or Anchor Rode Anchor Cable or Anchor Chain) is attached at one end to the vessel and at the other end to the anchor. 

The Anchor Watch is when an Officer remains on deck at night when the ship is at anchor to safeguard the vessel. This can mean everything from staying alert to intruders to making sure the anchor is not dragging and moving the ship to keeping an eye out for other vessels who may be dragging or sailing too close.

An Anchor Windlass is a mechanical device that operates on a pulley system and is used to raise and lower the anchor and chain down to and up from the sea bed. This system consists of a barrel with a chain or cable wound around it and is operated using a belt or crankshaft either manually or by motor.   

 An Anti-Exposure Suit (also called an Exposure Suit) is a garment designed to protect the wearer from an extreme environment. For example from wet and cold environments found at sea specifically in evacuation or rescue operations or in diving. Depending on the type of suit and the situation it has been designed for the garment may provide buoyancy total isolation from the environment or thermal insulation.  

Anti-Fouling Paint is a type of paint that is manufactured using specific agents to prevent the growth and attachment of organisms on a vessel’s hull.

An Anti-Fouling System is a device treatment paint or coating that controls or prevents the attachment of organisms on a vessel’s hull.

An Anti-Heeling System is used during cargo operations - i.e. during the loading and unloading of freight - to ensure that the ship’s heeling angle is kept to a minimum. This is important as excessive heeling could result in rolling cargo being damaged containers getting jammed in cell guides or ramps being twisted.

An Anti-Rack Spacer System is a system that can be used to connect two 20-foot shipping containers to create one single 40-foot container.

An Anti-Roll Tank is a tank that is fitted onto a vessel with the aim of improving that tank's response to roll motion. The rate of water transferred to the port side of the tank to the starboard side is slowed by baffles whilst the tank itself is designed so that a greater quantity of water remains on the ship’s higher side.

An Appendage is any part of a ship that protrudes from the hull below the waterline. This includes propellers the rudder shafts bilge keels struts and sonar domes.

The Apron is an area that is directly in front or behind a wharf shed onto which cargo is lifted. The cargo is unloaded or loaded onto a vessel from the front Apron and into and out of trucks or railroad cars from the rear Apron.

ARPA stands for Automatic Radar Plotting Aid - a computerized add-on feature to the Radar. ARPA identifies the ship’s course and speed and a target's course and speed and calculates the collision avoidance data. This makes it much easier for humans rather than calculating the data themselves.

Arrest or ship arrest refers to a court order in which a vessel is ‘arrested’ and held under state authority in a port in the face of a pending present or future claim that relates to the vessel. The reasons for a ship’s arrest can be due to anything from a claim by creditors to the vessel’s unseaworthiness.

The Articles of Agreement is the document which contains all information relating to the terms of agreement between the Master (Captain) of the vessel and the crew. 

A ship’s Assembly Station is an area in which passengers and crew must meet in the event of an alarm emergency or announcement.

Astern can variously mean behind a ship located at or towards the stern of a ship or the act of a ship moving backwards.

Generally used to describe cargo Athwartships is to be in a position across a vessel from side to side at right angles to the keel.

Similar to an Atrium in land-based architecture this is a public area with a high roof. In nautical terms the height spans three or more open decks.

An Auto Container is a shipping container used for the transportation of cars and other vehicles.

 An Automatic Identification System (AIS) is a navigational aid and automated tracking system that is used for the identification of vessels and navigational marks. It displays other vessels in the vicinity of a ship whilst also showing the ship it is located on to other vessels with AIS in that area. AIS is a broadcast transponder system that operates in the VHF mobile maritime band autonomously and continually.  

An Automatic Radar Plotting Aid (ARPA) is a marine radar technology designed to replace the manual plotting of targets. The ARPA uses radar contacts to calculate the course speed and closest point of approach (CPA) to various tracked objects. This enables whoever is steering or navigating a vessel to monitor the screen and take action if there is a potential chance of collision with that object.

An Auto Mooring System makes the mooring and unmooring of vessels a faster process reducing the time spent in port and therefore fuel consumption and emissions. The system is controlled remotely from the bridge of the ship or by a location on shore. 

 An Autopilot (or Automatic Pilot) is a self-steering device system used for automatic navigation. They come in varying degrees of complexity and sophistication although any Autopilot should be able to maintain a vessel on a pre-set compass course. More advanced Autopilots gather data from the ship’s instruments or connect to GPS receivers. The system will be able to tell the difference between the vessel’s ordered course and the actual course and will automatically adjust the rudder so that it moves to an angle that is proportional to the discrepancy.   

A vessel’s Auxiliaries are equipment such as motors engines winches and pumps etc. They have a part to play in the running of the vessel alongside the main propulsive machinery - such as boilers and engines on a steam installation.

Avast is a nautical term. It is an order to immediately stop doing something.

Awash is a term used to describe it when a vessel is so low in the water that the water is washing across the deck.