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The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of mass. Its original use as a measurement of volume has continued in the capacity of cargo ships and in terms such as the freight ton. It can also be used as a measure of energy, for truck classification, or as a colloquial term. It is derived from the ''tun'', the term applied to a barrel of the largest size. This could contain a volume between , which could weigh around and occupy some of space.〔(【引用サイトリンク】title=Naval Architecture for All ). "Historically, a very important and standard cargo for European sailing vessels was wine, stored and shipped in casks called tuns. These tuns of wine, because of their uniform size and their universal demand, became a standard by which a ship's capacity could be measured. A tun of wine weighed approximately 2,240 pounds, and occupied nearly 60 cubic feet." (Gillmer, Thomas (1975). ''Modern Ship Design''. United States Naval Institute.) "Today the ship designers standard of weight is the long ton which is equal to 2,240 pounds."〕 In the United Kingdom the ton is defined as (avoirdupois pounds). From 1965 the UK embarked upon a programme of metrication and gradually introduced metric units, including the tonne (metric ton), defined as 1000 kg (2,204.6 lbs). The UK Weights and Measures Act 1985 explicitly excluded from use for trade many units and terms, including the ton and the term "metric ton" for "tonne".〔A Dictionary of Weights, Measures, and Units, edited by Donald Fenna, Oxford University Press〕 In the United States and formerly Canada〔(【引用サイトリンク】title=Weights and Measures Act: Canadian units of measure )〕 a ton is defined to be . Where confusion is possible, the 2240 lb ton is called "long ton" and the 2000 lb ton "short ton"; the tonne is distinguished by its spelling, but usually pronounced the same as ton, hence the US term "metric ton". In the UK the final "e" of "tonne" can also be pronounced (/ˈtʌnɪ/),〔The Oxford English Dictionary 2nd ed. lists both /tʌn/ and /ˈtʌnɪ/ as pronunciations of "tonne"〕 or "metric ton" when it is necessary to make the distinction. Where accuracy is required the correct term must be used, but for many purposes this is not necessary: the metric and long tons differ by only 1.6%, and the short ton is within 11% of both. The ton is the heaviest unit of weight referred to in colloquial speech. The term "ton" is also used to refer to a number of units of volume, ranging from in capacity. It can also be used as a unit of energy, expressed as an equivalent of coal burnt or TNT detonated. In refrigeration, a ton is a unit of power, sometimes called a ''ton of refrigeration''. It is the power required to melt or freeze one short ton of ice per day. The refrigeration ton·hour is a unit of energy, the energy required to melt or freeze short ton of ice. ==Units of mass/weight== There are several similar units of mass or volume called the ton: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ton」の詳細全文を読む スポンサード リンク
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