NATIONAL FLAG – The flag carried by a ship to show her nationality.
NEOBULK – Shipments consisting entirely of units of a single commodity, such as
cars, lumber, or scrap metal.
NET CAPACITY – The number of tons of cargo which a vessel can carry when loaded in salt water to her summer freeboard marks. Also called cargo carrying capacity, cargo deadweight, useful deadweight.
NET TONNAGE – Equals gross tonnage minus deductions for space occupied by crew accommodations, machinery, navigation equipment and bunkers. It represents space available for cargo (and passengers). Canal tolls are based on net (registered) tonnage.
NON-CONFERENCE LINE – A shipping line which operates on a route served by a liner conference but which is not a member of that conference.
NON-LINER SERVICE – A shipping service that does not operate to a fixed itinerary or regular schedule. Someone once compared a non-liner service to a taxi service, going here, going there, anywhere to pick up a farefreight, whereas a Liner Service is like a bus service travelling to regular stops at regular times and on a regular turnaround route. See also Liner Service.
NORSKE VERITAS – Norwegian classification society.
NPA – National Ports Authority of South Africa
NRT – Net registered tons. This tonnage is frequently shown on ship registration papers; it represents the volumetric area available for cargo at 100 cubic feet = 1 ton. It often is used by port and canal authorities as a basis for charges.
NSRI – National Sea Rescue Institute.
NVO – Non-vessel-operating common carrier, a ships agent, conducts business for
the ship but does not operate the vessel.
NVOCC – Non Vessel Operating (Common) Container Carriers – a carrier issuing bills of lading for carriage of goods on vessels that he neither owns nor operates.
OBO SHIP – A multipurpose ship that can carry ore, heavy dry bulk goods and oil. Although more expensive to build, they ultimately are more economical because they can make return journeys with cargo instead of empty.
OCEAN WAYBILL – A document, issued by a shipping line to a shipper which serves as a receipt for the goods and evidence of the contract carriage.
OFFICER – Any of the licensed members of the ship's complement.
OFF-LOAD – Discharge of cargo from a ship.
OFF-HIRE or DOWNTIME – When a ship is temporarily out of operation, in accordance with the terms of the relevant charterparty, with a loss of agreed hire as a result.
OFFSHORE SERVICE VESSELS – Special vessels employed for the exploration, development or continuous production of subsea oil and gas.
OILER – An unlicensed member of the engine room staff who oils and greases bearings and moving parts of the main engine and auxiliaries. Most of this work is nowadays done automatically and the oiler merely insures it operates correctly.
OIL RECORD BOOK – A book or log kept by the master of an oil tanker wherein every discharge or escape of oil is recorded.
OIL TANKER – A ship designed for the carriage of oil in bulk, her cargo space consisting of several or many tanks. Tankers load their cargo by gravity from the shore or by shore pumps and discharge using their own pumps.
OPEN RATES – Pricing systems that are flexible and not subject to conference approval. Usually applied to products in which tramps are substituted for liners.
OPEN REGISTRY – A term also described as "flag of convenience" or "flag of necessity" to denote registry in a country which offers favourable tax, regulatory, and other incentives to ship owners from other nations.
OPERATOR – The holder of a freight contract with a cargo shipper.
ORE CARRIER – A large ship designed to be used for the carriage of ore. Because of the high density of ore, ore carriers have a relatively high centre of gravity to prevent them from rolling heavily at sea with possible stress to the hull.
ORE-BULK – OIL CARRIER – See OBO
ORE-OIL CARRIER – A ship designed to carry either ore or oil in bulk.
ORDINARY SEAMAN – A deck crewmember that is subordinate to the Able Bodied Seamen.
OVERTONNAGING – A situation where there are too many ships generally or in a particular trade for the level of available cargoes.