Two lines are perpendicular if they cross at 90 degree angles.
A coordinate graph has two perpendicular lines, or axes, labeled with number and called number lines. The horizontal axis is called the x-axis. The vertical axis is called the y-axis. The point where the x-axis and y-axis intersect is called the origin. I'm doing this in school now!
Two coplanar lines that never intersect are called called parallel lines.
An intersection is the point at which two or more lines touch or cross, therefore, lines are intersecting when they cross each-other.
Two lines cross or intersect at a point.
The location two lines cross or intersect is called a vertex.
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Lines that cross each other at 90 degrees are perpendicular lines.