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 ...

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.mathopenref.com/coordvertical.html

Definiton and equation for a **vertical line** in coordinate geometry.

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.varsitytutors.com/hotmath/hotmath_help/topics/horizontal-vertical-lines

Equations of horizontal and **vertical lines** only have one variable. The equation x
= 4 represents a **vertical line** which crosses the x-axis at the point (4, 0).

www.ixl.com/math/algebra-1/graph-a-horizontal-or-vertical-line

Fun math practice! Improve your skills with free problems in 'Graph a horizontal or
**vertical line**' and thousands of other practice lessons.