Plus–minus sign

The plus–minus sign or plus-or-minus sign (±) and the complementary minus-or-plus sign (∓) are symbols with broadly similar multiple meanings. In mathematics, the ± sign generally indicates a choice of exactly two possible values, one of which is obtained through addition and the other through subtraction. The ∓ is typically used only in tandem with the ± sign and indicates that in the case that the ± is a +, the ∓ would be a − (and vice-versa). In statistics and experimental sciences, the ± sign commonly indicates the confidence interval or uncertainty bounding a range of possible errors 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 chess, the ± sign indicates a clear advantage for the white player; the complementary minus-plus sign (∓) indicates a clear advantage for the black player. Other meanings occur in other fields, including medicine, engineering, chemistry, electronics, linguistics, and philosophy.