Ship

Ship, vessel that is buoyant in the water and used to transport people or cargo from one place to another via rivers, lakes, or oceans. Traditionally, ships were distinguished from boats by size—any buoyant vessel small enough to fit on board a ship was considered a boat. However, common usage has blurred the distinction between boats and ships, and today the difference between them is arbitrary.

Square-Rigger
Shown sailing near Fredriksted, Saint Croix, the square-rigger Denmark is a modern example of a 15th-century sailing ship with rectangular sails on the mainmast, foremast, and rear mizzenmast.

From prehistoric craft made from animal skins stretched over wooden frames to nuclear-powered aircraft carriers that transport 5,000 people and 85 airplanes, ships have always reflected the values and technologies of the societies that built them. Ancient traders of the Mediterranean built swift-sailing ships with large cargo holds. Their warring successors added oars to increase maneuverability in battle. The Spanish and Portuguese built small, seaworthy craft to carry their best sailors to new lands, then huge merchant vessels to haul the newly claimed riches, and finally fleets of warships to protect their growing wealth. At the end of the 16th century, shipbuilders changed their focus to passenger service as they sought to accommodate the increasing number of people immigrating to Australia and the Americas. They shifted from sail power to steam power and built ships that crossed the ocean in about one-fourth the time of their predecessors. When the jet airplane drastically reduced ship travel in the 20th century, shipbuilders again focused on the transport of cargo, turning out large tankers, the most massive ships ever afloat.

Despite their seemingly endless variety, all ships share a few basic elements. All ships have a main body, or hull, capable of displacing an amount of water equal to or greater than its own weight and the weight of its cargo. At the front end of the hull is the bow (or prow), and at the rear end is the stern. A ship’s size is expressed in terms of the dimensions of its hull—that is, its length, breadth, and volume in tons (calculated by dividing the cubic footage of the hull by 100). All ships also have a steering system and a propulsion system—that is, a device or system of devices that moves them through the water. Like ships themselves, hulls, propulsion systems, and steering systems grew more complex through time.