noun Any symbol used to group some of the terms in an expression, indicating that that part of the calculation should be done before other parts, or that the Roman numeral underneath should be multiplied by 1,000.
noun A horizontal line over the top of some of the terms in an expression, indicating that that part of the calculation is to be done before other parts (in modern mathematical notation confined to use in radicals: x+y).
noun The horizontal line between the numerator and denominator in a fraction.
noun A horizontal line placed over one or more digits of a decimal expansion to indicate that those digits repeat indefinitely (the repetend).
0.3‾=0.333…
noun A horizontal line placed over a complex number or expression to denote its complex conjugate.
2+3i‾=2−3i
noun A horizontal line drawn over two letters to denote the line segment joining them.
AB‾ is the line segment between points A and B
noun A horizontal line placed over a symbol or expression to denote logical negation (complement).