en.wikipedia.org/wiki/Vertical_bar

The vertical bar ( | ) is a computer character and glyph with various uses in mathematics, computing, and typography. It has many names, often related to particular meanings: Sheffer stroke (in logic), verti-bar, vbar, stick, broken bar, vertical line, vertical slash, bar, glidus, obelisk, or pipe ...

en.wikipedia.org/wiki/Horizontal_and_vertical

The usage of the inter-related terms horizontal and vertical as well as their symmetries and asymmetries vary with ...

www.khanacademy.org/math/algebra/two-var-linear-equations/hor-and-ver-lines-alg1/v/examples-of-slopes-and-equations-of-horizontal-and-vertical-lines

Worked examples identifying the equations and slope of horizontal and vertical lines.

www.mathwarehouse.com/algebra/linear_equation/vertical-line.php

Graphs, equations and properties of vertical lines explained with pictures and examples.

virtualnerd.com/algebra-1/linear-equation-analysis/intercept/horizontal-vertical-lines/vertical-line-definition

You may be able to guess that vertical lines are lines that go straight up and down, but did you know that all vertical lines have the same slope? In this tutorial ...

www.mathsteacher.com.au/year8/ch15_graphs/05_hor/ver.htm

Plotting a horizontal line and plotting a vertical line.

www.coolmath.com/algebra/08-lines/08-graphing-horizontal-vertical-lines-01

Horizontal and Vertical Lines. What if we want to graph this? y = -2. Hmm... It doesn't look like there's enough there! Where's the x? We're used to these: Ax + By ...

www.mathopenref.com/coordvertical.html

Definiton and equation for a vertical line in coordinate geometry.

mathforum.org/cgraph/cslope/horizontal.html

Horizontal and Vertical Lines. Lines that never slant up or down are called horizontal lines. Here is a picture of some horizontal lines: ...