The displacement or displacement tonnage of a ship is its weight based on the amount of water its hull displaces at varying loads. It is measured indirectly using Archimedes' principle by first calculating the volume of water displaced by the ship then converting that value into weight displaced. Traditionally, various measurement rules have been in use, giving various measures in long tons. Today, metric tonnes are more used.
Ship displacement varies by a vessel's degree of load, from its empty weight as designed (known as "Lightweight tonnage") to its maximum load. Numerous specific terms are used to describe varying levels of load and trim, detailed below.
The process of determining a vessel's displacement begins with measuring its draft This is accomplished by means of its "draft marks" (or "load lines"). A merchant vessel has three matching sets: one mark each on the port and starboard sides forward, midships, and astern. These marks allow a ship's displacement to be determined to an accuracy of 0.5%.
The draft observed at each set of marks is averaged to find a mean draft. The ship's hydrostatic tables show the corresponding volume displaced. To calculate the weight of the displaced water, it is necessary to know its density. Seawater (1025 kg/m3) is more dense than fresh water (1000 kg/m3); so a ship will ride higher in salt water than in fresh. The density of water also varies with temperature.
There are terms for the displacement of a vessel under specified conditions:
A Chinese treasure ship (Chinese: 寶船/宝船; pinyin: bǎochuán) was a type of large wooden ship in the fleet of admiral Zheng He, who led seven voyages during the early 15th-century Ming dynasty.
The size and dimensions of the treasures are heavily debated. According to British scientist, historian and sinologist Joseph Needham, the purported dimensions of the largest of these ships were 135 metres (440 ft) by 55 metres (180 ft), which would make them at least twice as long as the largest European ships at the end of the sixteenth century. In fact, such dimensions would make the treasure ships larger than the largest wooden boats ever built, even 19th century steel-reinforced ones. These dimensions have thus been challenged, on engineering grounds by experts and on the reliability of their sources (the first reference to Zheng He's ship length are from a novel dating more than a hundred years after Zheng He's voyage); some have claimed they could not have been more than 60–75 metres (195–245 ft) or that they could only have been used on special occasions in the relative safety of the lower Yangtze River. In 1962 a large rudder post was unearthed in the Treasure Ship Yard in Nanjing. As it is 11 metres long, it has been claimed that such dimensions correspond with a 200 metres (660 ft) long ship, although objections have again been raised.Displacement (fluid)
In fluid mechanics, displacement occurs when an object is immersed in a fluid, pushing it out of the way and taking its place. The volume of the fluid displaced can then be measured, and from this, the volume of the immersed object can be deduced (the volume of the immersed object will be exactly equal to the volume of the displaced fluid).
An object that sinks displaces an amount of fluid equal to the object's volume. Thus buoyancy is expressed through Archimedes' principle, which states that the weight of the object is reduced by its volume multiplied by the density of the fluid. If the weight of the object is less than this displaced quantity, the object floats; if more, it sinks. The amount of fluid displaced is directly related (via Archimedes' principle) to its volume.
In the case of an object that sinks (is totally submerged), the volume of the object is displaced. In the case of an object that floats, the amount of fluid displaced will be equal in weight to the displacing object.
Archimedes' principle, a physical law of buoyancy, states that any body completely or partially submerged in a fluid (gas or liquid) at rest is acted upon by an upward, or buoyant, force the magnitude of which is equal to the weight of the fluid displaced by the body. The volume of displaced fluid is equivalent to the volume of an object fully immersed in a fluid or to that fraction of the volume below the surface of an object partially submerged in a liquid. The weight of the displaced portion of the fluid is equivalent to the magnitude of the buoyant force. The buoyant force on a body floating in a liquid or gas is also equivalent in magnitude to the weight of the floating object and is opposite in direction; the object neither rises nor sinks. If the weight of an object is less than that of the displaced fluid, the object rises, as in the case of a block of wood that is released beneath the surface of water or a helium-filled balloon that is let loose in the air. An object heavier than the amount of the fluid it displaces, though it sinks when released, has an apparent weight loss equal to the weight of the fluid displaced. In fact, in some accurate weighing, a correction must be made in order to compensate for the buoyancy effect of the surrounding air. The buoyant force, which always opposes gravity, is nevertheless caused by buoyancy. Fluid pressure increases with depth because of the (gravitational) weight of the fluid above. This increasing pressure applies a force on a submerged object that increases with depth. The result is buoyancy.List of aircraft carriers of France
The following is a list of aircraft carriers of France.List of aircraft carriers of the Royal Navy
The following is a list of fleet aircraft carriers of the Royal Navy of the United Kingdom.List of battlecruisers of Germany
The Kaiserliche Marine, the navy of the German Empire, built a series of battlecruisers in the first half of the 20th century. The battlecruiser type was an outgrowth of older armored cruiser designs; they were intended to scout for the main battle fleet and attack the reconnaissance forces of opposing fleets. Kaiser Wilhelm II insisted that the new battlecruisers be able to fight in the line of battle with battleships to counter Germany's numerical inferiority.SMS Von der Tann was the first German battlecruiser, built in 1908–1910. The Kaiserliche Marine eventually built four more battlecruisers before the start of the First World War to serve with the High Seas Fleet, and another two were completed during the conflict. A further seven were planned, including four of the Mackensen and three of the Ersatz Yorck-class ships. Two of the Mackensens—the name ship and Graf Spee—were launched but never completed, and the other two were in earlier stages of work when they were canceled towards the end of the war. Serious work never began on the three Ersatz Yorck-class ships.Six of the seven battlecruisers completed before or during World War I saw relatively heavy combat, primarily in the North Sea. All of the ships, with the exception of Goeben, which had been assigned to the German Mediterranean Division, were assigned to the I Scouting Group under the command of Admiral Franz von Hipper. The unit conducted several raids of the English coast between 1914 and 1916, which culminated in the Battle of Jutland during 31 May – 1 June 1916, in which they were expected to draw parts of the British fleet onto the German battleship line. The German flagship Lützow was scuttled by her crew, on the way back to port, and the other ships were heavily damaged. For their own part, during the battle Von der Tann sank her counterpart HMS Indefatigable, Seydlitz sank Queen Mary, and Derfflinger and Lützow together destroyed Invincible. The five remaining battlecruisers—Von der Tann, Moltke, Seydlitz, Derfflinger, and Hindenburg—were interned with the bulk of the German fleet at the British naval base at Scapa Flow following the end of the war. The ships were subsequently scuttled by their crews in 1919 to prevent them from falling into the hands of the Allied Powers. Goeben was transferred to the Ottoman Navy at the outbreak of hostilities, and operated against the Russian Black Sea Fleet for the majority of the war. She was heavily damaged by British naval mines near the end of the war, but was repaired and went on to serve the Turkish Navy until the 1950s; she was eventually broken up for scrap in the 1970s.The eventual successor to the Kaiserliche Marine, the Kriegsmarine, considered building three O-class battlecruisers before the Second World War as part of the Plan Z buildup of the Navy. However, the outbreak of war in 1939 caused the plans to be shelved, and none of these ships were built.List of battlecruisers of Japan
The Imperial Japanese Navy (大日本帝国海軍) built four battlecruisers, with plans for an additional four, during the first decades of the 20th century. The battlecruiser was an outgrowth of the armoured cruiser concept, which had proved highly successful against the Russian Baltic Fleet in the Battle of Tsushima at the end of the Russo-Japanese War. In the aftermath, the Japanese immediately turned their focus to the two remaining rivals for imperial dominance in the Pacific Ocean: Britain and the United States. Japanese naval planners calculated that in any conflict with the U.S. Navy, Japan would need a fleet at least 70 percent as strong as the United States' in order to emerge victorious. To that end, the concept of the Eight-Eight fleet was developed, where eight battleships and eight battlecruisers would form a cohesive battle line. Similar to the German Imperial Navy (Kaiserliche Marine) and in contrast to the Royal Navy, the Japanese envisioned and designed battlecruisers that could operate alongside more heavily armoured battleships to counter numerical superiority.The first phase of the Eight-Eight plan began in 1910, when the Diet of Japan authorised the construction of one battleship (Fusō) and four battlecruisers of the Kongō class. Designed by British naval architect George Thurston, the first of these battlecruisers (Kongō) was constructed in Britain by Vickers, while the remaining three were constructed in Japan. Armed with eight 14-inch (360 mm) guns and with a top speed of 30 knots (35 mph; 56 km/h), they were the most advanced capital ships of their time. At the height of the First World War, an additional four battlecruisers of the Amagi class were ordered. The ships would have had a main battery of ten 16-inch (410 mm) guns, but none were ever completed as battlecruisers, as the Washington Naval Treaty limited the size of the navies of Japan, Britain and the United States. Before the Second World War, a further class of two battlecruisers were planned (Design B-65), but more pressing naval priorities and a faltering war effort ensured these ships never reached the construction phase.Of the eight battlecruiser hulls laid down by Japan (the four Kongō and four Amagi class), none survived the Second World War. Amagi was being converted to an aircraft carrier when its hull was catastrophically damaged by the Great Kantō earthquake in 1923 and subsequently broken up, while the last two of the Amagi class were scrapped in 1924 according to the terms of the Washington Treaty.Akagi was converted to an aircraft carrier in the 1920s, but was scuttled after suffering severe damage from air attacks during the Battle of Midway on 5 June 1942. The four Kongō-class ships were lost in action as well: two during the Naval Battle of Guadalcanal in November 1942, one by American submarine in November 1944, and one by American aircraft at Kure Naval Base in July 1945.List of battlecruisers of the Royal Navy
The battlecruiser was the brainchild of Admiral Sir John ("Jacky") Fisher, the man who had sponsored the construction of the world's first "all big gun" warship, HMS Dreadnought. He visualised a new breed of warship with the armament of a battleship, but faster, lighter, and less heavily armoured. The first three battlecruisers, the Invincible class, were laid down while Dreadnought was being built in 1906.This design philosophy was most successful in action when the battlecruisers could use their speed to run down smaller and weaker ships. The best example is the Battle of the Falkland Islands where Invincible and Inflexible sank the German armoured cruisers SMS Scharnhorst and SMS Gneisenau almost without damage to themselves, despite numerous hits by the German ships. They were less successful against heavily armoured ships, as was demonstrated by the loss of Invincible, Indefatigable, and Queen Mary during the Battle of Jutland in 1916. All three ships were destroyed by more heavily armoured German battlecruisers, with the British failure to prevent fires or explosions in the gun turrets from reaching the magazines also playing a role in the losses.Of the battlecruisers built before the First World War, the Invincible class and Indefatigable class all had 6 inches (152 mm) of armour on their waterline, a top speed of 25 knots (46 km/h; 29 mph), and eight 12-inch (305 mm) guns. The more advanced battlecruisers—the two Lion-class ships, HMS Queen Mary, and HMS Tiger—all had an armour belt of 9 inches (229 mm), speeds over 28 knots (52 km/h; 32 mph), and eight 13.5-inch (343 mm) guns. The Renown and Courageous classes, built during the war, were begun when Admiral Fisher was appointed First Sea Lord for the second time in late 1914. Each of these classes in turn served as the fastest capital ships in the world and were heavily armed with four or six 15-inch (381 mm) guns, but they paid for their speed and armament by having less armour than battleships. HMS Hood was laid down during the war, but was extensively reworked with more armour based on the experience gained at the Battle of Jutland, and was not completed until after the war.Following the war, the British planned to build the G3 class, which had the same armament and armour as battleships of the time and were rated as battlecruisers only by comparison to the more heavily armoured and slower battleships also planned. They were cancelled as they exceeded the tonnage limits of the Washington Naval Treaty. Of the first nine battlecruisers, only HMS Tiger survived the Washington Treaty and into the 1930s. The three Courageous-class ships were converted to aircraft carriers during the 1920s and only Repulse, Renown and Hood served in the Second World War as battlecruisers. All three went through substantial refits between the wars. Hood was lost in the battle of the Denmark Strait, Repulse was sunk by Japanese aircraft at the start of the war in the Pacific, and Renown survived the war to be scrapped in 1948.List of battlecruisers of the United States
The United States Navy began building a series of battlecruisers in the 1920s, more than a decade after their slower and less heavily armed armored cruisers had been rendered obsolete by the Royal Navy's Invincible-class battlecruisers. Construction of these ships was abandoned under the terms of an armaments limitation treaty, though two were completed as aircraft carriers. The US Navy subsequently ordered six "large cruisers"—which are often considered battlecruisers by historians—in 1940, of which only two entered service.
At first unconvinced of the importance of the superior speed of the British battlecruisers, the US Navy changed its position after evaluating the new type of ship in fleet exercises and Naval War College wargames, and after the Japanese acquisition of four Kongō-class battlecruisers in the early 1910s. The Secretary of the Navy initially refused the General Board's suggested procurement of several battlecruisers, but fleet exercises revealed that the Navy lacked forces that could effectively find and track an enemy fleet in any weather, and a consensus gradually emerged that battlecruisers would be ideal for this role. Battlecruisers were effective when concentrating their fire on an enemy fleet's leading ships, as the Japanese armored cruisers had done to the Russians at the Battle of Tsushima in 1905. Another role envisioned was tracking down and destroying enemy commerce raiders. British experience during the Battle of the Falkland Islands in late 1914 and the Battle of Dogger Bank the following year, where British battlecruisers caught and destroyed German armored cruisers, confirmed all these capabilities.
So when Congress authorized a large naval building program in 1916, six Lexington-class battlecruisers were included. None were completed before the arms-limiting Washington Naval Treaty was ratified in 1922; four were broken up on the slipway and two were converted into aircraft carriers. The treaty forestalled any further development of battlecruisers for the next decade and a half, but a number of countries experimented with "cruiser-killer" ships in the late 1930s that were designed to destroy the post-London Naval Treaty heavy cruisers. These designs were formally designated as battlecruisers by the Dutch and Soviets and as large cruisers by the Japanese and Americans, but all were roughly equivalent and all were commonly called battlecruisers. The US Navy's main impetus for the Alaska class was the threat posed by Japanese cruisers raiding its lines of communication in the event of war. Heavy cruisers were also the most likely surface threat to aircraft carriers making independent raids, so a cruiser-killer was also an ideal carrier escort. Reports of a Japanese equivalent reinforced the Navy's desire for these ships. Two were commissioned in time to serve during the last year of World War II, but were decommissioned two years after the war.List of battleships of Greece
In the early 20th century, the Greek Navy embarked on an expansion program to counter a strengthening of Greece's traditional rival, the Ottoman Empire. The Ottomans ordered a new dreadnought battleship, Reşadiye; in response, Greece ordered the dreadnought Salamis from a German shipyard. The Ottomans acquired the ex-Brazilian Rio de Janeiro and renamed her Sultân Osmân-ı Evvel. Greece responded with a second battleship ordered in France, Vasilefs Konstantinos, built to the same design as the French Bretagne class. As the Ottomans had a significant head start in battleship construction, the Greek Navy purchased two obsolete American pre-dreadnoughts—USS Mississippi and Idaho—as a stop-gap measure in June 1914. The ships were renamed Kilkis and Lemnos, respectively.
Greek naval plans were interrupted by the outbreak of World War I in August 1914, however. Work halted on Vasilefs Konstantinos in August and on Salamis in December 1914. As a result, Kilkis and Lemnos were the only battleships delivered to Greece. Greece remained neutral for the first three years of World War I, though in October 1916, France seized the Greek Navy and disarmed both of the battleships. They remained inactive for the rest of the war. Both ships saw service in 1919–1922 during the Greco–Turkish War. They continued to serve with the fleet until the early 1930s, when they were reduced to secondary roles. Lemnos became a barracks ship while Kilkis became a training ship. During the German invasion of Greece in April 1941, both ships were attacked and sunk in Salamis by Ju 87 Stuka dive-bombers. The two old battleships were scrapped after the end of the war.List of battleships of the United States Navy
The United States Navy began the construction of battleships with USS Texas in 1892, but the first battleship under that designation would be USS Indiana. Texas and USS Maine, commissioned three years later, were part of the New Navy program of the late 19th century, a proposal by then Secretary of the Navy William H. Hunt to match Europe's navies that ignited a years-long debate that was suddenly settled in Hunt's favor when the Brazilian Empire commissioned the battleship Riachuelo. In 1890, Alfred Thayer Mahan's book The Influence of Sea Power upon History was published and significantly influenced future naval policy—as an indirect of its influence on Secretary Benjamin F. Tracy, the Navy Act of June 30, 1890 authorized the construction of "three sea-going, coast-line battle ships" which became the Indiana class. The Navy Act of July 19, 1892 authorized construction of a fourth "sea-going, coast-line battle ship", which became USS Iowa. Despite much later claims that these were to be purely defensive and were authorized as "coastal defense ships", they were almost immediately used for offensive operations in the Spanish–American War. By the start of the 20th century, the United States Navy had in service or under construction the three Illinois-class and two Kearsarge-class battleships, making the United States the world's fifth strongest power at sea from a nation that had been 12th in 1870.Except for Kearsarge, named by an act of Congress, all U.S. Navy battleships have been named for states, and each of the 48 contiguous states has had at least one battleship named for it except Montana; two battleships were authorized to be named Montana but both were cancelled before construction started. Alaska and Hawaii did not become states until 1959, after the end of battleship building, but the battlecruiser, or "Large Cruiser," USS Alaska was built during World War II and her sister, USS Hawaii, was begun but never completed. The pre-dreadnoughts USS Zrinyi (formerly the Austrian SMS Zrínyi), USS Radetzky (formerly the Austrian SMS Radetzky), and USS Ostfriesland (formerly the German SMS Ostfriesland), taken as prizes of war after World War I, were commissioned in the US Navy, but were not assigned hull classification symbols.
No American battleship has ever been lost at sea, though four were sunk during the attack on Pearl Harbor. Of these, only USS Arizona (BB-39) and USS Oklahoma (BB-37) were permanently destroyed as a result of enemy action. Several other battleships have been sunk as targets, and USS Utah, demilitarized and converted into a target and training ship, was permanently destroyed at Pearl Harbor. The hulk of Oklahoma was salvaged and was lost at sea while being towed to the mainland for scrapping. Two American-built pre-dreadnought battleships, USS Mississippi (BB-23) and her sister USS Idaho (BB-24), were sunk in 1941 by German bombers during their World War II invasion of Greece. The ships had been sold to Greece in 1914, becoming Kilkis and Lemnos respectively.List of cruisers of Austria-Hungary
Between the 1870s and 1910s, the Austro-Hungarian Navy built a series of cruisers of various types, including small torpedo cruisers, protected cruisers, fast scout cruisers and large armored cruisers. The first modern cruisers were the three Zara class begun in the late 1870s; a fourth vessel, Lussin, followed in the early 1880s. These ships proved to be unsatisfactory in service, and so to gain experience building effective vessels, the Navy ordered the two Panther-class cruisers from Britain. These were used as the basis for the domestically-built Tiger. Toward the end of the 1880s, the Navy shifted from building small torpedo cruisers to larger protected and armored cruisers, the first of which were the two Kaiser Franz Joseph I-class cruisers. These provided the basis for the armored cruisers Kaiserin und Königin Maria Theresia, Kaiser Karl VI, and Sankt Georg, built between 1891 and 1905.
In the mid-1890s, the three Zenta-class cruisers were built; these proved to be the last protected cruisers of the Austro-Hungarian fleet. In the mid-1900s, the Navy started building scout cruisers, starting with Admiral Spaun, which proved to be a disappointment owing to her unreliable engines. The subsequent design, the Novara class, rectified the problem and they shouldered much of the burden of the Adriatic Campaign during World War I. They were the last class of cruisers completed before the war, as the Ersatz Zenta class was cancelled after the outbreak of hostilities, just two months after they had been authorized.List of current ships of the Royal Canadian Navy
The Royal Canadian Navy (RCN) is tasked to provide maritime security along the Pacific, Atlantic and Arctic coasts of Canada, exercise Canada's sovereignty over the Arctic archipelago, and support Canada's multi-national and bilateral interests overseas. The RCN fleet comprises the Pacific Fleet at Canadian Forces Base (CFB) Esquimalt, and the Atlantic Fleet at CFB Halifax. CFB Esquimalt is located on Vancouver Island, in British Columbia, and is home to 15 vessels and 6,000 staff, the headquarters for Maritime Forces Pacific, Her Majesty's Canadian (HMC) Dockyard Esquimalt, Fleet Maintenance Facility – Cape Breton (FMF-CB), Fire Fighting and Damage Control School, the Naval Officer Training Centre (NOTC Venture), and extensive housing. CFB Halifax is home port for the 18 vessels of the Canadian Atlantic Fleet and situated in Halifax, Nova Scotia. CFB Halifax employs 7,000 civilians and military staff, and hosts the Canadian Atlantic Fleet headquarters, HMC Dockyard Halifax, FMF Cape Scott, extensive maritime research facilities, an ammunition depot, and the four maritime squadrons of the Royal Canadian Air Force that serve aboard the fleet. The Canadian Armed Forces are currently constructing a new naval facility at Nanisivik, Baffin Island, to provide a summer port for RCN patrols in the Canadian arctic.With the loss of command-and-control and resupply capabilities in 2015, the RCN is classified as a Rank 5 navy (offshore regional coastal defence) on the Todd-Lindberg classification system, dropping from Rank 3 (multiregional power projection). In 2011, the government restored the traditional name of the Royal Canadian Navy, removed at the unification of the Canadian Armed Forces in 1968. Commissioned vessels are designated as 'Her Majesty's Canadian Ship' (HMCS), minor ships as 'Patrol Craft Training' (PCT) and auxiliaries as 'Canadian Forces Auxiliary Vessel' (CFAV).List of escort carriers of the Royal Navy
The escort aircraft carrier, also called a "jeep carrier" or "baby flattop" in the USN or "Woolworth Carrier" by the RN, was a small and slow type of aircraft carrier used by the Royal Navy in the Second World War. They were typically half the length and one-third the displacement of the larger fleet carriers. While they were slower, less armed, unarmoured and carried fewer aircraft, they were less expensive and could be built more quickly. This was their principal advantage, as escort carriers could be completed in greater numbers as a stop-gap when fleet carriers were scarce. However, the lack of protection made escort carriers particularly vulnerable and several were sunk with great loss of life. The light carrier (hull classification symbol CVL) was a similar concept to escort carriers in most respects, but they were designed for higher speeds for deployment with fleet carriers.
Escort carriers were too slow to keep up with the main forces consisting of fleet carriers, battleships, and cruisers. Instead, they were used to defend convoys from enemy threats such as submarines and planes. In the invasions of mainland Europe and Pacific islands, escort carriers provided air support to ground forces during amphibious operations. Escort carriers also served as backup aircraft transports for fleet carriers and ferried aircraft of all military services to points of delivery.
In addition, escort carriers such as HMS Vindex and HMS Nairana played an important role in hunter-killer anti-submarine sweeps in company with RN and RCN destroyers, frigates and corvettes (e.g. 6th Canadian Escort Group and 2nd British Escort Group). HMS Vindex is credited with the sinking, or taking part in the sinking, of four U-boats (U344, U653, U765, U394). Escort carriers should not be confused with the Merchant Aircraft Carrier or CAM ship.List of monitors of the Royal Navy
This is a list of monitors of the Royal Navy of the United Kingdom.List of pre-dreadnought battleships of the Royal Navy
This is a list of the pre-dreadnought battleships of the Royal Navy and covers the ships between the monitors and the launching of HMS Dreadnought in 1906.List of protected cruisers of Germany
The German Imperial Navy (Kaiserliche Marine) built a series of protected cruisers in the 1880s and 1890s, starting with the two ships of the Irene class. The Navy only completed two additional classes of protected cruisers, comprising six more ships: the unique Kaiserin Augusta, and the five Victoria Louise-class ships. The type was then superseded by the armored cruiser at the turn of the century, beginning with Fürst Bismarck. Because of limited budgets in the pre-Tirpitz era, the German Navy attempted to build vessels that could serve as overseas cruisers and scouts for the fleet, though the ships were not satisfactory. The protected cruiser designs generally copied developments in foreign navies. The Victoria Louise design resembled contemporary German battleships, which favored smaller-caliber main guns and more secondary guns than on their foreign counterparts.Most of the German protected cruisers served on overseas stations throughout their careers, primarily in the East Asia Squadron in the 1890s and 1900s. Prinzess Wilhelm participated in the seizure of the Kiautschou Bay concession in November 1897, which was used as the primary base for the East Asia Squadron. Kaiserin Augusta, Hertha, and Hansa assisted in the suppression of the Boxer Rebellion in China in 1900, and Vineta saw action during the Venezuela Crisis of 1902–1903, where she bombarded several Venezuelan fortresses. Irene, Prinzess Wilhelm, and Kaiserin Augusta were relegated to secondary duties in the 1910s, while the Victoria Louise class was used to train naval cadets in the 1900s. All eight ships were broken up for scrap in the early 1920s.List of seaplane carriers of the Royal Navy
This is a list of Royal Navy seaplane carriers.Tonnage
Tonnage is a measure of the cargo-carrying capacity of a ship. The term derives from the taxation paid on tuns or casks of wine. In modern maritime usage, "tonnage" specifically refers to a calculation of the volume or cargo volume of a ship. Tonnage should not be confused with displacement, which refers to the actual weight of the vessel. Tonnage is commonly used to assess fees on commercial shipping.