Double Bar

The double bar symbol | is used to denote certain kinds of norms in mathematics (e.g., ||x|| or ||x||_2). It is also used to denote parallel lines, as in A∥B, and in an older notation for the covariant derivative. In this work, the notation ||A|| or ||f|| is reserved for matrix and function norms, respectively.

See also

Bar, Covariant Derivative, Norm, Matrix Norm, Parallel, Single Bar

Explore with Wolfram|Alpha


Bringhurst, R. The Elements of Typographic Style, 2nd ed. Point Roberts, WA: Hartley and Marks, p. 277, 1997.

Referenced on Wolfram|Alpha

Double Bar

Cite this as:

Weisstein, Eric W. "Double Bar." From MathWorld--A Wolfram Web Resource.

Subject classifications