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(unicode:±) The plus-minus sign ((unicode:±)) is a mathematical symbol with multiple meanings. *In mathematics, it generally indicates a choice of exactly two possible values, one of which is the negation of the other. *In experimental sciences, the sign commonly indicates the confidence interval or error in a measurement, often the standard deviation or standard error.〔 The sign may also represent an inclusive range of values that a reading might have. *In engineering the sign indicates the tolerance, which is the range of values that are considered to be acceptable, safe, or which comply with some standard, or with a contract.〔Engineering tolerance〕 *In chemistry the sign is used to indicate a racemic mixture. *In chess, the sign indicates a clear advantage for the white player; the complementary sign ∓ indicates the same advantage for the black player.〔.〕 The sign is normally pronounced "plus or minus". ==History== A version of the sign, including also the French word "ou" (meaning "or") was used in its mathematical meaning by Albert Girard in 1626, and the sign in its modern form was used as early as William Oughtred's ''Clavis Mathematicae'' (1631).〔.〕 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-minus sign」の詳細全文を読む スポンサード リンク
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