What is "plus-minus sign"

n. (context mathematics English) the symbol ±, meaning "plus or minus", used to indicate the precision of an approximation (as in "The result is 10 ± 0.3", meaning the result is somewhere between 10 - 0.3, that is, 9.7, and 10 + 0.3, that is, 10.3), or as a convenient shorthand for a quantity with two possible values of opposing sign and identical magnitude (as in "The roots of the equation x² - 4 = 0 are ±2").

The plus-minus sign (±) 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.
• In botany it is used in morphological descriptions to notate "more or less".
• 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".