A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished from boats, based on size, shape, load capacity, and purpose. Ships have supported exploration, trade, warfare, migration, colonization, imperialism, and science. After the 15th century, new crops that had come from and to the Americas via the European seafarers significantly contributed to the world population growth.[1] Ship transport is responsible for the largest portion of world commerce.

As of 2016, there were more than 49,000 merchant ships, totaling almost 1.8 billion dead weight tons. Of these 28% were oil tankers, 43% were bulk carriers, and 13% were container ships

Ships are typically larger than boats, but there is no universally accepted distinction between the two. Ships generally can remain at sea for longer periods of time than boats.[3] A legal definition of ship from Indian case law is a vessel that carries goods by sea.[4] A common notion is that a ship can carry a boat, but not vice versa.[5] A ship is likely to have a full-time crew assigned.[6] A US Navy rule of thumb is that ships heel towards the outside of a sharp turn, whereas boats heel towards the inside[7] because of the relative location of the center of mass versus the center of buoyancy.[8][9] American and British 19th century maritime law distinguished "vessels" from other crafts; ships and boats fall in one legal category, whereas open boats and rafts are not considered vessels.[10]

In the Age of Sail, a full-rigged ship was a sailing vessel with at least three square-rigged masts and a full bowsprit; other types of vessel were also defined by their sailplan, e.g. barque, brigantine, etc.[11]

A number of large vessels are usually referred to as boats. Submarines are a prime example.[12] Other types of large vessels which are traditionally called boats include Great Lakes freighters, riverboats, and ferryboats.[10] Though large enough to carry their own boats and heavy cargoes, these vessels are designed for operation on inland or protected coastal waters.

In most maritime traditions ships have individual names, and modern ships may belong to a ship class often named after its first ship.