Glossary

A warship designed for carrying, launching, and landing aircraft.

A large ceramic jar of the ancient Mediterranean used for bulk storage of olives, wine, fish sauce, and preserved fruit. The shape, design, and contents of amphorae (among other objects) found in ancient ships provide many clues about the extent and course of seaborne trade from the 3rd millennium bce to the Byzantine era.

Extra iron or steel plate used to protect a ship from gunfire. The thickness of iron varied according to the part of the ship around which it was placed; vital areas included crew and engine spaces, magazines, and gun turrets.

A three-, four-, or five-masted vessel square rigged on all but the aftermost mast, which is fore-and-aft rigged.

A vessel of three to six masts, square rigged on the foremast, and fore-and-aft rigged on the others.

A hybrid capital ship of the early 20th century with the firepower of a battleship, but with armor protection sacrificed for greater speed.

A ship fit to lie in the line of battle; the most heavily armed and stoutly built ship of the day. The battleship concept lasted from the 17th century until after World War II, when the development of torpedoes, naval aviation, and missiles rendered the battleship obsolete.

A fore-and-aft rig in which the mainsail is triangular in shape; also called Marconi rig. (See also gaff rig.)

A two-masted vessel, square rigged on both masts.

A two-masted vessel, square rigged on the foremast, and fore-and-aft rigged on the main.

A unit of distance equal to one-tenth of a nautical mile, or approximately 200 yards or 200 meters.

The most important class of warship in a given era. The term originally referred to ships fit to sail in the line of battle, or battleships. In the 20th century, battleships were eclipsed by aircraft carriers.

A relatively small Portuguese vessel of the 15th and 16th centuries setting lateen sails on two or three masts and sometimes a square sail on the foremast. Highly maneuverable, caravels helped to make possible the voyages of the early Portuguese and Spanish discoverers.

A large seagoing vessel of the 14th century that combined northern European and Mediterranean shipbuilding techniques. Carracks resembled the northern cog, but they were constructed frame first and carried more than one mast. By the 16th century, they carried three masts and high stern and forecastles. Carracks were forerunners of galleons.

A short-barreled ship's gun developed by the Carron Company in Scotland. Though of limited range, carronades were enormously destructive to ships' timbers and were originally known as "smashers." Within two years, 429 ships of the Royal Navy—"where a short range is ever the distance chosen"—carried carronades. The addition of carronades was not reflected in the nominal rate of a ship; a 54-gun ship mounting 10 carronades was still designated a "44." (See also gun and rate.)

A method of hull construction in which the longitudinal strakes forming the skin of the hull are flush at the edges. In carvel construction, the planks are fastened to a pre-erected frame. (See also clinker construction, frame-first construction, and shell-first construction.)

A fixed armored enclosure designed to protect a ship's guns from hostile fire.

A method of hull construction in which the longitudinal strakes forming the hull overlap each other and are "clenched" to each other with iron nails. In clinker construction, the hull is built first; frames were sometimes inserted afterward. (See also carvel construction, frame-first construction, and shell-first construction.)

The name given to a variety of square-rigged merchant ships built chiefly for speed. During the heyday of the American clipper ship, between 1845 and 1860, the term applied to "sharp-built" ships that sacrificed cargo capacity for speed and carried a maximum of canvas and correspondingly large crews. The primary impetus for the clipper era were the gold rushes in California and Australia. In the late 1860s the British built smaller clippers for the tea trade between China and England.

A type of capacious merchant vessel that originated in Germany and gradually spread throughout the Baltic and to the Mediterranean. It is characterized by high sides, a relatively flat bottom, and a single square sail.

A type of hull construction consisting of an iron or steel frame and wooden planking.

A steam engine in which the steam expands first in a high-pressure cylinder, and then in a low-pressure cylinder.

A type of warship falling between battleships and destroyers in size, armament, and speed. Cruisers were designed primarily for reconnaissance while with the fleet, or for commerce protection, commerce raiding, and patrolling on overseas stations.

A single-masted vessel similar to a sloop but usually setting double headsails. Patrol vessels of the U.S. Coast Guard are also called cutters.

Relatively small warships, torpedo-boat destroyers originated as small, fast ships whose primary function was to protect larger ships from torpedo attack. Their roles later expanded to include antisubmarine and antiaircraft warfare and convoy protection.

The standard method of measuring warships. Displacement tonnage is the volume of water displaced by a vessel, the weight of the water displaced being equal to the weight of the object displacing it. (See also tonnage.)

A square-rigged merchant ship that combined large carrying capacity with relatively sharp hull design. Built especially for the California grain trade in the quarter century following the American Civil War (1865-1890), Down Easters were so called because they were built in Maine, which is downwind and east of the major East Coast ports.

A small aircraft carrier designed chiefly to provide air cover for convoys and amphibious operations, and used also to ferry aircraft and train pilots.

A sail set parallel to the centerline of a vessel. Fore-and-aft vessels are simpler to rig than square-rigged vessels, require a smaller crew, and can sail closer to the direction from which the wind is blowing.

Originally, a built-up structure comprising several decks in the forward part of a ship, from which archers or gunners could fire into an enemy ship. (A sterncastle aft served the same function.) In more modern usage, the forecastle (pronounced and often written "focsle") was the crew's quarters in the forward part of a ship.

A transverse rib that forms part of the skeleton of a ship's hull.

A method of construction in which the internal framework, or skeleton, of a ship's hull is constructed first, with the hull planking being attached afterward. (See also carvel construction, clinker construction, and shell-first construction.)

A small combatant ship; a 4th- or 5th-rate ship in the Royal Navy. In the age of sail, frigates sailed with the fleet as reconnaissance vessels and were known as "the eyes of the fleet." In battle, they stood away from the line to relay signals from the flagship to other ships in the line who could not see the flagship because of gunsmoke. Frigates were also used for convoy protection and commerce raiding. In modern parlance, a frigate is a ship designed to protect shipping from aircraft and submarines.

A fore-and-aft rig in which the primary sails abaft the mast are trapezoidal in shape: the bottom of the sail is attached to the boom, the luff (or forward edge) to the mast, and the head to a spar called a gaff. (See also Bermuda rig.)

A hybrid type of 16th-century vessel employing both a full sailing rig and oars for propulsion.

A full-rigged vessel that evolved in Europe around the 16th century and is the immediate ancestor of the full-rigged ship. Galleons' higher length-to-beam ratio and lower fore- and sterncastles made them more maneuverable than carracks.

A relatively narrow vessel driven primarily by oars. Galleys evolved in the ancient Mediterranean, and the galley par excellence was the Greek "trieres," or trireme.

A generic term for a carriage-mounted gun in sailing warships. Guns were rated according to the weight of shot fired, anywhere from 1-pound antipersonnel guns to 42 pounders. In the sailing navy, guns were mounted in broadside, and the most effective use was to arrange the ship in a line to enable each to fire at the same target; hence the battle line, or line of battle. Developed in the 19th century, rifled guns (measured by the caliber, or internal diameter of the gun barrel) were housed in rotating turrets, which gave the guns wider arcs of fire. (See also carronade and rate.)

A measure of mechanical power. A vessel's horsepower is measured in various ways, depending on the type of engine. The power of a steam engine is expressed as indicated horsepower (ihp), the work of the steam in the cylinder, or nominal horsepower (nhp), an expression of power derived by formula. Steam turbines are measured by shaft horsepower (shp), the power at the crankshaft as indicated by a torsion meter. Diesel engines are often measured by brake horsepower (bhp), determined by a brake attached to the shaft coupling. Effective horsepower (ehp) is the actual work done by an engine propelling a vessel.

A warship with a wooden hull sheathed in iron for protection against gunfire.

A triangular fore-and-aft sail carried on a stay leading from the topmast head to the bow or bowsprit.

A temporary rig used to replace a damaged mast or spar.

A two-masted yacht with a tall mainmast and a shorter mizzen mast.

A Scandinavian seagoing cargo ship of the Viking era. Knorrs were shorter, beamier, and deeper than longships.

A unit of measure used to express the speed of a ship in nautical miles per hour. One international nautical mile is defined as 6,076.1155 feet, or approximately 1.15 statute (land) miles. A knot is generally taken to mean a rate of speed, and some argue that "knots per hour" is an incorrect expression. The argument is a pedantic one; many ship's logs record speeds in knots per hour. The accompanying table shows the time (in days and hours) required to travel a given distance at various speeds.

By custom, the speed of vessels on the Great Lakes and inland rivers of the United States is measured in statute miles per hour.

See clinker construction.

A triangular fore-and-aft sail set from a long spar attached to a short mast and found in traditional vessels of the Iberian Peninsula, Mediterranean, and Indian Ocean.

A unit of distance equal to 3 nautical miles. The actual distance has varied at different times: Columbus's league was about 3.18 miles, that of Magellan 3.5 miles.

A passenger steam- or motorship that runs on an established route, such as between Europe and the United States.

A vertical pole or spar from which sails are set. In a square-rigged vessel, masts are often composed of separate sections: lower mast, topmast, topgallant mast, and royal mast. Masts are named, from bow to stern, foremast, mainmast, mizzen mast, and jigger mast. In some five-masted vessels, the middle mast is called, simply, a middle mast. Driver and spanker masts are also found on six-masted vessels.

The generic name for a ship that sails in regular service between two ports. The development of the transatlantic packet trade can be dated to 1817, when the Black Ball Line inaugurated service with ships sailing on a predetermined schedule regardless of whether they were booked to capacity.

A steamboat driven by a paddle wheel. The most common arrangement is a pair of wheels mounted on either side of the hull. American riverboats frequently have a single sternwheel.

The unlawful seizure of property or ships on the high seas. Cf. privateer.

One possessing a letter of marque from his government and thereby entitled to seize enemy shipping on the high seas. Under the Hague Convention of 1907, merchantmen armed for purposes other than self-defense are classified as warships.

A long piece of sawn timber used in the construction of the hull and for decking. A strake can be made up of one or more planks.

A steam engine in which the steam expands through four cylinders.

A class of sailing warship, particularly in the Royal Navy, dependent on the number of guns mounted. The number of guns carried by a ship of a given rate changed from time to time. In 1779 it was as follows:

Ships of 60 guns and above were considered fit to lie in the battle line and referred to simply as vessels "of the line." Fourth- and 5th-rates were classed as frigates. Smaller combatants included sloops (ship-rigged, mounting 8-18 guns), bombs (fitted with mortars for bombing shoreside targets), and fireships (older vessels set on fire and sailed into an enemy fleet to destroy their ships). (See also carronade and gun.)

A capacious, heavily armed, and well-manned merchant ship of the Dutch East India Company (Verenigde Oostindische Compagnie, or VOC) designed for the long roundtrip (retour) voyage from the Netherlands to the East Indies.

A medieval merchant sailing ship, as distinct from a longship or an oared galley.

A device hung on the centerline at the stern and used to turn a vessel. (See also steering oar.)

A vessel of two to seven masts, fore-and-aft rigged on each. A topsail schooner also sets square sails on the foremast. (See also barkentine.)

A method of hull construction in which the hull is formed without a frame. In shell-first construction, strakes either overlap, fastened to one another by clenched nails (clinker or lapstrake construction), or they form a smooth skin, fastened edge to edge by a complex system of mortise-and-tenon joinery. (See also carvel construction, clinker construction, and frame-first construction.)

A generic term usually referring to any large seagoing vessel.

A full-rigged sailing ship fit to lie in the line of battle; a sailing battleship. A ship of the line carried 60 or more guns, and was rated as a 1st-, 2nd-, or 3rd-rate ship.

A vessel having three, four, or five masts and setting square sails on each. From the deck up, these are course, topsail (sometimes split into lower and upper), topgallant (sometimes split), royal, and skysail. In very light airs, some clipper ship captains would rig moonrakers above the skysails.

A single-masted vessel setting a mainsail and a single jib, or headsail.

A three-masted full-rigged warship, smaller than a frigate and rating 8 to 20 guns.

An explosive device carried at the end of a spar and placed against an enemy ship before being detonated.

A quadrilateral sail set from a yard. Although a square-rigger can carry more sail than a fore-and-aft rigged vessel of comparable size, it is more dependent on favorable (following) winds.

A triangular fore-and-aft sail set from a stay, a piece of standing rigging leading forward from, and providing longitudinal support for, a mast.

An oar mounted on the side of a ship (usually the right—steering board, or starboard—side) toward the stern and used for turning a ship. (See also rudder.)

A continuous row of hull planking (in a wooden ship) or plating (in an iron or steel ship) running fore and aft.

A warship capable of operating underwater for long periods. During the two world wars, the submarine's primary armament consisted of torpedoes and small-caliber deck guns for work when surfaced. Many subs could be adapted for mine-laying operations, and a few also carried collapsible aircraft in deck hangars and midget submarines. In the nuclear era, strategic force submarines have been armed with intercontinental ballistic missiles that can be launched from underwater.

A vertical piece of wood against which a rowing oar pivots.

In merchant ships, tonnage is usually an expression of a ship's capacity or volume. The word has its origins in the medieval "tun," or wine cask, tunnage being the number of tuns a vessel could carry. Tonnage rules vary enormously. In the 18th century, tonnage was referred to as "burthen." This was replaced by "Builder's Old Measurement," abbreviated "bm" or later "om," to distinguish it from new measurement (nm). One ton is now generally understood to equal 100 cubic feet.

Gross register tonnage (grt) is the whole cubic capacity of all enclosed spaces of a ship, including the entire room under the deck from stem to sternpost as well as that of the poop or bridge-house, a forecastle, or any other erection. Net register tonnage (nrt) is the capacity under deck available for stowing cargo only, and not including engine room spaces, passenger accommodations, or crew spaces.

Unlike cubic measures of tonnage, deadweight tonnage (dwt) is a measure of the weight of a vessel's cargo. This is determined by calculating the volume of water displaced by a vessel when "light" and when full of cargo. Because the water displaced is equal to the weight of the object displacing it, the difference in displacement figures is equal to the weight of the cargo. Deadweight tonnage is usually used only in reference to bulk cargo carriers such as oil tankers. (See also displacement tonnage.)

A self-propelled, underwater explosive device launched from surface ships, submarines, and aircraft. Developed in the late 19th century, torpedoes proved enormously effective against both merchant shipping and warships.

A steam engine in which the steam expands gradually and successively through three cylinders. Steam is first supplied to a high-pressure cylinder, then it passes into an intermediate-pressure cylinder at a lower pressure and finally into a low-pressure cylinder.

In the age of fighting sail, if a ship was upwind of another it was said to have the weather gauge; the downwind or leeward ship had the lee gauge. The advantage of having the weather gauge was that a ship's guns could be aimed at the enemy's hull, often below the waterline. The guns of the leeward ship fired into the rigging, where damage was less serious.

A spar fastened to a mast perpendicular to the centerline of a vessel and from which square sails are set. The ends of a yard are called yardarms.

A two-masted yacht similar in appearance to a ketch but with a smaller mizzen mast set abaft the rudderpost.