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The pound or pound-mass (abbreviations: lb, lb''m'', lbm, ℔) is a unit of mass used in the imperial, United States customary and other systems of measurement. A number of different definitions have been used, the most common today being the international avoirdupois pound which is legally defined as exactly , and which is divided into 16 avoirdupois ounces.〔 The unit is descended from the Roman ''libra'' (hence the abbreviation "lb"); the name ''pound'' is a Germanic adaptation of the Latin phrase ''libra pondo'', "a pound by weight".〔''Oxford English Dictionary'', ''s.v.'' 'pound'〕 Usage of the unqualified term ''pound'' reflects the historical conflation of mass and weight. This accounts for the modern distinguishing terms ''pound-mass'' and ''pound-force''. ==Current use== The United States and countries of the Commonwealth of Nations agreed upon common definitions for the pound and the yard. Since 1 July 1959, the international avoirdupois pound has been defined as exactly .〔National Bureau of Standards, (Appendix 8 ); National Physical Laboratory, PH Bigg ''et al.'' : ''(Re-determination of the values of the imperial standard pound and of its parliamentary copies in terms of the international kilogramme during the years 1960 and 1961 )''; Sizes.com: ''(pound avoirdupois ).''〕 In the United Kingdom, the use of the international pound was implemented in the Weights and Measures Act 1963.〔Quoted by Laws LJ in (【引用サイトリンク】title= An avoirdupois pound is equal to 16 avoirdupois ounces and to exactly 7,000 grains. The conversion factor between the kilogram and the international pound was therefore chosen to be divisible by 7, and an (international) grain is thus equal to exactly . In the UK, the process of metrication and European units of measurement directives were expected to eliminate the use of the pound and ounce, but in 2007 the European Commission abandoned the requirement for metric-only labelling on packaged goods there, and allowed for dual metric–imperial marking to continue indefinitely. When used as a measurement of body weight the UK practice remains to use the stone of 14 avoirdupois pounds as the primary measure e.g. "11 stone 4 pounds", rather than "158 pounds" (as done in the US),〔Christine Hopkins, Ann Pope, Sandy Pepperell (2013). "Understanding Primary Mathematics". p. 195. Routledge.〕 or "72 kilograms" as used elsewhere. The US has not adopted the metric system despite many efforts to do so, and the pound remains widely used as one of the key United States customary units. 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「Pound (mass)」の詳細全文を読む スポンサード リンク
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