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The litre (International spelling) or liter (American spelling) (SI symbols L or l,〔 commonly abbreviated as ltr) is an SI accepted metric system unit of volume equal to 1 cubic decimetre (dm3), 1,000 cubic centimetres (cm3) or 1/1,000 cubic metre. A cubic decimetre (or litre) occupies a volume of 10×10×10 centimetres (see figure) and is thus equal to one-thousandth of a cubic metre. The original French metric system used the litre as a base unit. The word ''litre'' is derived from an older French unit, the ''litron'', whose name came from Greek via Latin, and which equalled approximately 0.831 litres. The litre was also used in several subsequent versions of the metric system and is accepted for use with the SI,〔(Bureau International des Poids et Mesures, 2006 ), p. 124. ("Days" and "hours" are examples of other non-SI units that SI accepts.)〕 although not an official SI unit—the SI unit of volume is the cubic metre (m3). The spelling used by the International Bureau of Weights and Measures is "litre",〔 a spelling which is shared by almost all English-speaking countries. The less common spelling of "liter" is more predominantly used in American English.〔The Metric Conversion Act of 1985 gives the United States Secretary of Commerce the responsibility of interpreting or modifying the SI for use in the United States. The Secretary of Commerce delegated this authority to the Director of the National Institute of Standards and Technology (NIST) ((Turner, 2008 )). In 2008, the NIST published the U.S. version ((Taylor and Thompson, 2008a )) of the English text of the eighth edition of the Bureau International des Poids et Mesures (BIPM) publication ''Le Système International d’ Unités (SI)'' ((BIPM, 2006 )). In the NIST publication, the spellings ‘meter’, ‘liter’ and ‘deka’ are used rather than ‘metre’, ‘litre’ and ‘deca’ as in the original BIPM English text ((Taylor and Thompson, 2008a ), p. iii). The Director of the NIST officially recognized this publication, together with (Taylor and Thompson (2008b) ), as the ‘legal interpretation’ of the SI for the United States ((Turner, 2008 )).〕 One litre of liquid water has a mass of almost exactly one kilogram, due to the gram being defined in 1795 as one cubic centimetre of water at the temperature of melting ice. Subsequent redefinitions of the metre and kilogram mean that this relationship is no longer exact.〔 ==Definition== A litre is defined as ''a special name for a cubic decimetre'' or 10 centimetres × 10 centimetres × 10 centimetres, (1 L ≡ 1 dm3 ≡ 1000 cm3). Hence 1 L ≡ 0.001 m3 ≡ 1000 cm3, and 1 m3 (i.e. a cubic metre, which is the SI unit for volume) is exactly 1000 L. From 1901 to 1964, the litre was defined as the volume of one kilogram of pure water at maximum density and standard pressure. The kilogram was in turn specified as the mass of a platinum/iridium cylinder held at Sèvres in France and was intended to be of the same mass as the 1 litre of water referred to above. It was subsequently discovered that the cylinder was around 28 parts per million too large and thus, during this time, a litre was about 1.000028 dm3. Additionally, the mass-volume relationship of water (as with any fluid) depends on temperature, pressure, purity and isotopic uniformity. In 1964, the definition relating the litre to mass was abandoned in favour of the current one. Although the litre is not an official SI unit, it is accepted by the CGPM (the standards body that defines the SI) for use with the SI. CGPM defines the litre and its acceptable symbols. A litre is equal in volume to the millistere, an obsolete non-SI metric unit customarily used for dry measure. 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「litre」の詳細全文を読む スポンサード リンク
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