vinculum

noun11

1. •
   A ligament that limits the movement of an organ or part.
2. •
   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: √).
3. •
   The horizontal line between the numerator and denominator in a fraction.
4. •
   A horizontal line placed over one or more digits of a decimal expansion to indicate that those digits repeat indefinitely (the repetend).
5. •
   A horizontal line placed over a complex number or expression to denote its complex conjugate.
6. •
   A horizontal line drawn over two letters to denote the line segment joining them.
7. •
   A horizontal line placed over a symbol or expression to denote logical negation (complement).
8. •
   (historical) A horizontal line placed over the characteristic (integer part) of a common logarithm to indicate that the characteristic is negative while the mantissa (decimal part) remains positive. Historically used to simplify the use of logarithm tables.
9. •
   (Australia) A symbol in the shape of an elongated letter "S" (∫) or pair of hooks (⌠⌡) drawn on plans to join non-contiguous sections of land that are to be treated as a single parcel.
10. •
    (no longer used) 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.
11. •
    (figurative, no longer used) A bond or tie that unifies.