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A billion is a number with two distinct definitions: *1,000,000,000, i.e. one thousand million, or (ten to the ninth power), as defined on the short scale. This is now generally the meaning in both British and American English.〔(【引用サイトリンク】title=How many is a billion? )〕 *1,000,000,000,000, i.e. one million million, or (ten to the twelfth power), as defined on the long scale. This is one thousand times larger than the short scale billion, and equivalent to the short scale trillion. American English always uses the short scale definition but British English has employed both versions. Historically, the United Kingdom used the long scale billion but since 1974 official UK statistics have used the short scale. Since the 1950s the short scale has been increasingly used in technical writing and journalism, although the long scale definition still enjoys common usage. Other countries use the word ''billion'' (or words cognate to it) to denote either the long scale or short scale billion. For details, see Long and short scales – Current usage. Another word for one thousand million is ''milliard'', but this is used much less often in English than ''billion''. Some languages, such as French or German, use ''milliard'' (or a related word) for the short scale billion, and ''billion'' (or a related word) for the long scale billion. Thus the French or German ''billion'' is a thousand times larger than the modern English billion. ==History== According to the ''Oxford English Dictionary'', the word ''billion'' was formed in the 16th century (from ''million'' and the prefix ''bi-'', "two"), meaning the second power of a million (). This long scale definition was similarly applied to ''trillion'', ''quadrillion'' and so on. The words were originally French, and entered English around the end of the 17th century. Later, French arithmeticians changed the words' meanings, adopting the short scale definition whereby three zeros rather than six were added at each step, so a billion came to denote a thousand million (), a trillion , and so on. This new convention was adopted in the United States in the 19th century, but Britain retained the original long scale use. France, in turn, reverted to the long scale in 1948.〔OED (1989) entry for "billion".〕 In Britain, however, under the influence of American usage, the short scale came to be increasingly used. In 1974, Prime Minister Harold Wilson confirmed that the government would use the word ''billion'' only in its short scale meaning (one thousand million). In a written answer to Robin Maxwell-Hyslop MP, who asked whether official usage would conform to the traditional British meaning of a million million, Wilson stated: "No. The word 'billion' is now used internationally to mean 1,000 million and it would be confusing if British Ministers were to use it in any other sense. I accept that it could still be interpreted in this country as 1 million million and I shall ask my colleagues to ensure that, if they do use it, there should be no ambiguity as to its meaning."〔 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「billion」の詳細全文を読む スポンサード リンク
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