Cargo ship
A cargo ship or freighter is a merchant vessel designed to transport goods, commodities, and materials across seas and oceans. These ships form the backbone of international trade, carrying the majority of global freight by volume. Cargo ships vary widely in size and configuration, ranging from small coastal vessels to massive ocean-going carriers, and are typically specialized for particular types of cargo, such as containers, bulk goods, or liquids. Modern cargo ships are constructed from welded steel and equipped with loading mechanisms such as cranes or gantries. With a typical service life of 25 to 30 years, they operate under complex logistical networks and international regulations, playing a critical role in the global economy and maritime infrastructure.
Definitions
The words cargo and freight have become interchangeable in casual usage. Technically, "cargo" refers to the goods carried aboard the ship for hire, while "freight" refers to the act of carrying of such cargo, but the terms have been used interchangeably for centuries.Generally, the modern ocean shipping business is divided into two classes:
- Liner business: typically container vessels, operating as "common carriers", calling at a regularly published schedule of ports. A common carrier refers to a regulated service where any member of the public may book cargo for shipment, according to long-established and internationally agreed rules.
- Tramp-tanker business: generally this is private business arranged between the shipper and receiver and facilitated by the vessel owners or operators, who offer their vessels for hire to carry bulk or break bulk to any suitable port in the world, according to a specifically drawn contract, called a charter party.
Classification of Cargo Ships
Cargo ships, also known as freighters, are classified according to the nature of the cargo they are designed to transport. Major categories include:Specialized cargo ship types
Size categories
Cargo ships are categorized partly by cargo or shipping capacity, partly by weight, and partly by dimensions. Maximum dimensions such as length and width limit the canal locks a ship can fit in, water depth is a limitation for canals, shallow straits or harbors and height is a limitation in order to pass under bridges. Common categories of dry cargo include:History
Cargo ships from the ancient world to the Mediaeval period
The ancient Mediterranean
The earliest records of waterborne activity mention the carriage of items for trade; the evidence of history and archaeology shows the practice to be widespread by the beginning of the 1st millennium BC, and as early as the 14th and 15th centuries BC small Mediterranean cargo ships like those of the long Uluburun ship were carrying 20 tons of exotic cargo; 11 tons of raw copper, jars, glass, ivory, gold, spices, and treasures from Canaan, Greece, Egypt, and Africa.Phoenician cargo ships enabled extensive Mediterranean trade from the 12th century BCE, carrying goods such as metals, glass, and textiles to colonies from Cyprus to Spain, even beyond the Pillars of Hercules, forming a vast maritime network central to Phoenician trade. Notably the broad‑beamed gaulos or “round ship,” were designed for stability, capacity, and long‑distance trade across the Mediterranean from c. 1200 BCE. Built primarily from cedar using mortise‑and‑tenon joinery, they featured deep hulls, high freeboards, and a single square sail complemented by oars for manoeuvring. Archaeological evidence, including iconography and wreck analysis, shows these vessels could carry bulk goods such as timber, metals, glassware, textiles, and luxury items, enabling the Phoenicians to dominate maritime commerce for centuries.
Following the Phoenicians, the Carthaginians became the dominant maritime traders of the western Mediterranean from the 6th century BCE, operating extensive routes to Iberia, Britain, and West Africa. Their broad‑beamed merchantmen, adapted from the Phoenician gaulos, featured sturdy hulls, deep holds, and single square sails, enabling the transport of bulk goods such as grain, metals, wine, and luxury items over long distances and through varied seasonal conditions.
Roman cargo ships, naves onerariae, were the backbone of the empire’s maritime supply network from the late Republic to the Imperial period. Broad‑hulled and relatively shallow‑draft for stability and harbour access, they were built with mortise‑and‑tenon joinery reinforced by iron and bronze fittings. Most carried a single large square sail on a central mast, though some larger vessels added a foremast for improved manoeuvrability. The largest naves frumentariae could exceed 50 metres in length and carry hundreds of tonnes, far surpassing the capacity of earlier Phoenician merchantmen. Purpose‑built variants transported grain, wine, oil, stone, and other bulk goods, ensuring the steady flow of staples from Egypt and North Africa to Rome’s urban population.
Between the collapse of the Western Roman Empire and the rise of Venice, Mediterranean cargo ship design evolved through a series of innovations introduced by successive maritime powers. In the early medieval period, the Byzantine Empire refined late Roman merchant hulls, drawing on the hydrodynamic qualities of the Dromon to produce lighter, faster vessels that could carry mixed cargo and passengers more efficiently. From the 7th century, the Arab Caliphates introduced the axial stern‑mounted rudder, likely derived from Chinese shipbuilding, alongside wider adoption of the lateen sail and hybrid hull forms blending Mediterranean and Indian Ocean traditions. These advances improved manoeuvrability, expanded seasonal sailing windows, and integrated Mediterranean trade into the Indian Ocean network.
The Italian maritime republics
By the 9th to 11th centuries, early Italian maritime republics such as Amalfi and Gaeta developed the nava, a broad‑beamed, high‑sided cargo carrier with reinforced framing for heavier loads, strengthening Italy–Levant trade. In the 11th to 13th centuries, Pisa and Genoa evolved the nava into the hulk, a capacious, ocean‑capable vessel, and experimented with merchant galleys that reduced oar banks in favour of expanded cargo space. By the 13th century, Genoa and Venice were building the carrack, a fully decked, multi‑masted ship combining square and lateen rigs with the stern rudder, enabling large‑scale, long‑distance trade beyond the Mediterranean and laying the foundation for the Age of Exploration.From the 12th to the 14th centuries, the Republic of Genoa emerged as one of the leading maritime powers of the Mediterranean, building a merchant fleet that rivalled Venice in both capacity and reach. Genoese shipyards produced a range of cargo vessels, including the navis, a broad‑beamed, deep‑hulled sailing ship for bulk goods, and the bucius, a smaller variant suited to coastal and regional trade. Merchant galleys, adapted from war designs, were employed for high‑value cargoes such as spices, textiles, and precious metals, combining speed with defensive capability on long‑distance routes to the Levant and the Black Sea. Genoa’s merchant marine was closely tied to its commercial colonies and trading posts, from the Crimean port of Caffa to North African harbours, and benefited from sophisticated financial instruments such as the loca, which allowed investors to share in the profits of individual voyages. By the late Middle Ages, Genoese shipwrights were contributing to the development of the carrack that would dominate Mediterranean and Atlantic trade in the 15th century.
From the 12th century, the Republic of Venice developed a highly organised merchant fleet that underpinned its dominance of Mediterranean trade. The state‑run muda convoys, sailing on fixed schedules to destinations such as Alexandria, Constantinople, and Bruges, combined cargo transport with armed protection. Venetian merchant galleys were long, narrow‑hulled vessels adapted from war galleys, with reduced oar banks, expanded holds, and large lateen sails, enabling the fast and secure carriage of high‑value goods including spices, silk, and precious metals. For bulk cargoes such as grain, timber, and salt, Venice employed broad‑beamed round ships, which evolved into the multi‑masted carrack by the 14th century. Central to this system was the Venetian Arsenal, a vast state‑owned shipyard operating on assembly‑line principles, capable at its peak of producing a fully fitted galley in a single day, ensuring the republic could maintain and rapidly replace its merchant fleet.
The desire to operate trade routes over longer distances, and throughout more seasons of the year, motivated improvements in ship design during the Middle Ages.
Mediaeval Northern Europe
In the Viking Age, long‑distance trade in northern waters was carried primarily by the knarr, a broad‑beamed, deep‑hulled cargo vessel distinct from the longship. Clinker‑built with overlapping planks and a single square sail, the knarr could carry 20–50 tonnes of cargo and was stable in open seas while retaining a shallow enough draft for river navigation and beaching. These ships enabled Norse merchants to move timber, furs, iron, and luxury goods from the Baltic to the Mediterranean, and across the North Atlantic to Iceland, Greenland, and Vinland. By the 10th century, the hulk appeared in records, possibly originating in the Low Countries, with strongly curved stem and stern and a capacious hull suited to bulk cargo.From the 12th century, the cog emerged along the Frisian and Saxon coasts, eventually replacing Viking‑type traders in most northern waters. Early cogs were single‑masted, square‑rigged, clinker‑built vessels with flat bottoms and high sides, allowing them to settle upright at low tide for easy loading and unloading, and offering greater cargo capacity and security from attack. By the 13th and 14th centuries, mature cogs with fore and aft castles became the workhorses of the Hanseatic League, carrying grain, beer, salt, timber, and wool between Baltic, North Sea, and English Channel ports. Late medieval hulks, particularly in the Baltic, grew to rival contemporary great ships in size, while retaining clinker construction traditions.
By the late 15th century, northern shipwrights began adopting the carvel‑built, multi‑masted carrack from Iberia and the Mediterranean, replacing the single‑masted cog on long‑distance routes, marking the transition from medieval to early modern ocean‑going cargo ships and enabling northern merchants to participate in emerging Atlantic trade networks. The carrack’s greater tonnage and improved seaworthiness allowed for heavier cargoes and extended voyages beyond the Baltic and North Sea.
In the late 16th century, Dutch shipbuilders developed the fluyt, a purpose‑built cargo vessel with a capacious hull, narrow upper works to reduce tolls, and minimal crew requirements. The fluyt became the workhorse of Baltic and North Sea trade, optimised for bulk goods such as grain, timber, and salt, and was instrumental in the Dutch Republic’s commercial dominance.