The single bar is a notation variously used to denote the absolute value , complex modulus , vector norm , determinant , or "divides" ().
Single Bar
See also
Bar, Divides, Double Bar, ParallelExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Single Bar." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/SingleBar.html