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The plus and minus signs (+ and −) are mathematical symbols used to represent the notions of positive and negative as well as the operations of addition and subtraction. Their use has been extended to many other meanings, more or less analogous. ''Plus'' and ''minus'' are Latin terms meaning "more" and "less", respectively. == History == Though the signs now seem as familiar as the alphabet or the Hindu-Arabic numerals, they are not of great antiquity. The Egyptian hieroglyphic sign for addition, for example, resembled a pair of legs walking in the direction in which the text was written (Egyptian could be written either from right to left or left to right), with the reverse sign indicating subtraction: Nicole Oresme's manuscripts from the 14th century show what may be one of the earliest uses of the plus sign "+".〔(The birth of symbols – Zdena Lustigova, Faculty of Mathematics and Physics Charles University, Prague )〕 In Europe in the early 15th century the letters "P" and "M" were generally used. The symbols (P with line ''p̄'' for ''più'', i.e., plus, and M with line ''m̄'' for ''meno'', i.e., minus) appeared for the first time in Luca Pacioli’s mathematics compendium, ''Summa de arithmetica, geometria, proportioni et proportionalità'', first printed and published in Venice in 1494. The + is a simplification of the Latin "et" (comparable to the ampersand &). The − may be derived from a tilde written over m when used to indicate subtraction; or it may come from a shorthand version of the letter m itself. In his 1489 treatise Johannes Widmann referred to the symbols − and + as ''minus'' and ''mer'' (Modern German ''mehr''; "more"): "was − ist, das ist minus, und das + ist das mer". A book published by Henricus Grammateus in 1518 makes another early use of + and − for addition and subtraction.〔(Earliest Uses of Various Mathematical Symbols )〕 Robert Recorde, the designer of the equals sign, introduced plus and minus to Britain in 1557 in ''The Whetstone of Witte'':〔.〕 "There be other 2 signes in often use of which the first is made thus + and betokeneth more: the other is thus made – and betokeneth lesse." 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「Plus and minus signs」の詳細全文を読む スポンサード リンク
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