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The metric system is an internationally agreed decimal system of measurement. It was originally based on the フランス語:''mètre des Archives'' and the フランス語:''kilogramme des Archives'' introduced by the First French Republic in 1799, but over the years the definitions of the metre and the kilogram have been refined, and the metric system has been extended to incorporate many more units. Although a number of variants of the metric system emerged in the late nineteenth and early twentieth centuries, the term is now often used as a synonym for "SI"〔The following abbreviations are taken from the French rather than the English texts: * SI: ''Le Système international d'unités'' * CGPM: ''Conférence générale des poids et mesures'' * CIPM: ''Comité international des poids et mesures'' * BIPM: ''Bureau international des poids et mesures'' * CIE: ''Commission Internationale de l'Eclairage ''〕 or the "International System of Units"—the official system of measurement in almost every country in the world. The metric system has been officially sanctioned for use in the United States since 1866, but the US remains the only industrialised country that has not adopted the metric system as its official system of measurement. Many sources also cite Liberia and Burma as the only other countries not to have done so. Although the United Kingdom uses the metric system for most official purposes, the use of the imperial system of measure, particularly among the public, is widespread and is permitted by the law. Although the originators intended to devise a system that was equally accessible to all, it proved necessary to use prototype units in the custody of national or local authorities as standards. Control of the prototype units of measure was maintained by the French government until 1875, when it passed to an inter-governmental organisation—the General Conference on Weights and Measures (CGPM).〔 From its beginning, the main features of the metric system were the standard set of inter-related base units and a standard set of prefixes in powers of ten. These base units are used to derive larger and smaller units that could replace a huge number of other units of measure in existence. Although the system was first developed for commercial use, the development of coherent units of measure made it particularly suitable for science and engineering. The uncoordinated use of the metric system by different scientific and engineering disciplines, particularly in the late 19th century, resulted in different choices of base units, even though all were based on the same definitions of the metre and the kilogram. During the 20th century, efforts were made to rationalise these units, and in 1960 the CGPM published the International System of Units, which has since then been the internationally recognised standard metric system. == Features == Although the metric system has changed and developed since its inception, its basic concepts have hardly changed. Designed for transnational use, it consisted of a basic set of units of measurement, now known as base units. Derived units were built up from the base units using logical rather than empirical relationships while multiples and submultiples of both base and derived units were decimal-based and identified by a standard set of prefixes. 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「metric system」の詳細全文を読む スポンサード リンク
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