ship

A ship is a large, self-propelled vessel designed to operate in open water, typically on oceans and major rivers. Unlike boats, which are launched and recovered, ships are permanently sea-going structures with their own power plants, navigation systems, and cargo or passenger handling equipment. The distinction between ship and boat is partly size (ships generally exceed 24 metres in length) but also capability: a ship is meant to venture far from shore and stay at sea for weeks or months without support.

Cargo ships and container vessels make up the bulk of commercial shipping. A typical general cargo ship might be 150 to 200 metres long, with a deadweight capacity of 15,000 to 50,000 tonnes. Container ships are larger, often 300+ metres, stacking boxes in bays and on deck. Bulk carriers, tankers, and specialized vessels like refrigerated ships (reefers) serve specific trades. Passenger ships range from small cruise vessels of 10,000 gross tonnage to mega-ships exceeding 200,000 tonnes.

A ship's hull is built from steel, aluminum, or composite materials depending on the service. The hull is divided into compartments by watertight bulkheads; breach of one compartment should not sink the vessel. Propulsion is almost always diesel-electric: a main engine drives a propeller through a shaft, with auxiliary engines for electricity and heating. Container ships and tankers often use slow-speed two-stroke engines running heavy fuel oil; smaller ships use medium-speed four-stroke engines. Modern tonnage increasingly fits fuel-efficient bulbous bows and optimized hull forms.

Crew size and capability vary enormously. A modern container ship might operate with 13 to 20 crew members (captain, deck officers, ratings, engine officers, ratings, and ratings), relying on automation and remote monitoring. Older cargo ships and some bulk carriers require larger crews. Tankers carry specialized officers for cargo handling. All ocean-going ships must meet international maritime law, including standards set by the International Maritime Organization (IMO) for stability, life-saving, pollution prevention, and crew training.

The term 'ship' itself comes from Anglo-Saxon roots and historically distinguished seagoing vessels from smaller craft. In modern usage, maritime law and classification societies (Lloyd's Register, DNV GL, ABS) define 'ship' by tonnage, service area, and crew requirements rather than a single threshold. A vessel operating exclusively in coastal waters or lakes may be called a ship by size but regulated as a smaller craft. Conversely, an ocean-going tug or anchor handler, despite modest size, may be subject to ship-class rules because of its deep-water role.