A vinculum is a horizontal line placed above multiple quantities to indicate that they form a unit. It is most commonly used to denote

1. A radical (),

2. Repeating decimals (),

3. The line segment joining two points and ,

4. The complex conjugate ,

5 Negation of a logical expression, ,

6. A line placed over a Roman numerals character indicating that the overlined character value should be multiplied by a factor of 1000.

The term "viculum" may also be used to refer to the horizontal line used to separate the numerator from the denominator in a stacked (as opposed to in-line) fraction.