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Density is a substance's mass per unit of volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume: where ρ is the density, m is the mass, and V is the volume. In some cases, density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight.
The litre or liter is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metres (m3). A cubic decimetre occupies a volume of 10 cm × 10 cm × 10 cm and is thus equal to one-thousandth of a cubic metre.
Ton is any of several units of measure of mass, volume or force. It has a long history and has acquired several meanings and uses.
United States customary units form a system of measurement units commonly used in the United States and most U.S. territories, since being standardized and adopted in 1832. The United States customary system developed from English units that were in use in the British Empire before the U.S. became an independent country. The United Kingdom's system of measures was overhauled in 1824 to create the imperial system, which was officially adopted in 1826, changing the definitions of some of its units. Consequently, while many U.S. units are essentially similar to their imperial counterparts, there are noticeable differences between the systems.
Volume is a measure of regions in three-dimensional space. It is often quantified numerically using SI derived units or by various imperial or US customary units. The definition of length and height (cubed) is interrelated with volume. The volume of a container is generally understood to be the capacity of the container; i.e., the amount of fluid that the container could hold, rather than the amount of space the container itself displaces. By metonymy, the term "volume" sometimes is used to refer to the corresponding region.
The stere or stère (st) is a unit of volume in the original metric system equal to one cubic metre. The stere is typically used for measuring large quantities of firewood or other cut wood, while the cubic meter is used for uncut wood. The name was coined from the Greek στερεός stereós, "solid", in 1795 in France as a metric analogue to the cord. The unit was introduced to remove regional disparities of this former unit, for which the length could vary greatly from 6 to 13.5 m. It is not part of the modern metric system (SI) and is no longer a legal unit in France, but remains used in the commerce of firewood.
Tonnage is a measure of the capacity of a ship, and is commonly used to assess fees on commercial shipping. 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. Although tonnage (volume) should not be confused with displacement, the long ton of 2,240 lb is derived from the fact that a "tun" of wine typically weighed that much.
The long ton, also known as the imperial ton or displacement ton, is a measurement unit equal to 2,240 pounds (1,016.0 kg). It is the name for the unit called the "ton" in the avoirdupois system of weights or Imperial system of measurements. It was standardised in the 13th century. It is used in the United States for bulk commodities.
The twenty-foot equivalent unit is a general unit of cargo capacity, often used for container ships and container ports. It is based on the volume of a 20-foot-long (6.1 m) intermodal container, a standard-sized metal box that can be easily transferred between different modes of transportation, such as ships, trains, and trucks.
A barrel is one of several units of volume applied in various contexts; there are dry barrels, fluid barrels, oil barrels, and so forth. For historical reasons the volumes of some barrel units are roughly double the volumes of others; volumes in common use range approximately from 100 to 200 litres. In many connections the term drum is used almost interchangeably with barrel.
English units were the units of measurement used in England up to 1826, which evolved as a combination of the Anglo-Saxon and Roman systems of units. Various standards have applied to English units at different times, in different places, and for different applications.
Both the British imperial measurement system and United States customary systems of measurement derive from earlier English unit systems used prior to 1824 that were the result of a combination of the local Anglo-Saxon units inherited from Germanic tribes and Roman units.
The cord is a unit of measure of dry volume used to measure firewood and pulpwood in the United States and Canada.
Dry measures are units of volume to measure bulk commodities that are not fluids and that were typically shipped and sold in standardized containers such as barrels. They have largely been replaced by the units used for measuring volumes in the metric system and liquid volumes in the imperial system but are still used for some commodities in the US customary system. They were or are typically used in agriculture, agronomy, and commodity markets to measure grain, dried beans, dried and fresh produce, and some seafood. They were formerly used for many other foods, such as salt pork and salted fish, and for industrial commodities such as coal, cement, and lime.
Gross tonnage is a nonlinear measure of a ship's overall internal volume. Gross tonnage is different from gross register tonnage. Neither gross tonnage nor gross register tonnage should be confused with measures of mass or weight such as deadweight tonnage or displacement.
Net tonnage is a dimensionless index calculated from the total moulded volume of the ship's cargo spaces by using a mathematical formula. Defined in The International Convention on Tonnage Measurement of Ships that was adopted by the International Maritime Organization in 1969, the net tonnage replaced the earlier net register tonnage (NRT) which denoted the volume of the ship's revenue-earning spaces in "register tons", units of volume equal to 100 cubic feet (2.83 m3). Net tonnage is used to calculate the port duties and should not be taken as less than 30 per cent of the ship's gross tonnage.
The hoppus cubic foot was the standard volume measurement used for timber in the British Empire and countries in the British sphere of influence before the introduction of metric units. It is still used in the hardwood trade in some countries. This volume measurement was developed to estimate what volume of a round log would be usable timber after processing, in effect attempting to ‘square’ the log and allow for waste. The hoppus ton (HT) was also a traditionally used unit of volume in British forestry. One hoppus ton is equal to 50 hoppus feet or 1.8027 cubic meters. Some shipments of tropical hardwoods, especially shipments of teak from Myanmar (Burma), are still stated in hoppus tons.
Ship measurements consist of a multitude of terms and definitions specifically related to ships and measuring or defining their characteristics.
The imperial and US customary measurement systems are both derived from an earlier English system of measurement which in turn can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure.
References
- ↑ "Glossary of Terms". Saia. Archived from the original on 2006-03-14. Retrieved 2024-07-21.
- ↑ "Glossary — National Air Cargo". Archived from the original on 2007-10-07. Retrieved 2007-05-11.