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Ships may occur collectively as fleets, flotillas or squadrons. Convoys of ships commonly occur.
A collection of ships for military purposes may comprise a navy or a task force.
People counting or grouping disparate types of ships may refer to the individual vessels as bottoms. Groups of sailing ships could comprise, say, a fleet of 40 sail. Groups of submarines (particularly German U-boats in the 1940s) may hunt in packs.
Ships, particulalry sailing ships, involve a rich and varied vocabulary of many technical terms. Many of the following terms link to more detailed discussions of nautical jargon.
Until the application of the steam engine to ships in the early 19th century, oars propelled galleys or the wind propelled sailing ships.
Before mechanisation, merchant ships always used sail, but as long as naval warfare depended on ships closing to ram or to fight hand-to-hand, galleys dominated in marine conflicts because of their maneuverability and speed. The Greek navies that fought in the Peloponnesian War used triremes, as did the Romans contesting the Battle of Actium. The use of large numbers of cannon from the 16th century meant that maneuverability took second place to broadside weight; this led to the dominance of the sail-powered warship.
The development of the steamship became a complex process, the first commercial success accruing to Robert Fulton's North River Steamboat (often called the " Clermont ") in the USA in 1807, followed in Europe by the 45-foot PS Comet of 1812. Steam propulsion progressed considerably over the rest of the 19th century. Notable developments included the condenser, which reduced the requirement for fresh water, and the multiple expansion engine, which improved efficiency. The paddle wheel gave way to the more powerful screw propeller. Further efficiencies resulted from the development of the marine steam turbine by Sir Charles Parsons, who demonstrated it on the 100-foot Turbinia at the Spithead Naval Review in 1897. This facilitated a generation of high-speed liners in the first half of the 20th century.
The marine diesel engine first came into use around 1912: either the Vulcanus or the Selandia (depending upon who you talk to) first deployed it. It soon offered even greater efficiency than the steam turbine but for many years had an inferior power-to-space ratio. About this period too, oil came into more general use and began to replace coal as the fuel of choice.
Most ships built since around 1960 have used diesel power or motors; one exception, the Queen Elizabeth 2 of 1968, started with steam turbines but subsequently converted to diesel as a cost-saving measure.
A few ships have used nuclear reactors, but this form of propulsion has caused concerns about safety and has only become common in large aircraft carriers and in submarines, where the ability to run submerged for long periods has obvious benefits.
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