Perpendicular lines are two lines that cross at exactly 90 degrees. The right angle is what defines them, not their direction on the page, so a pair of slanted lines can be perpendicular just as a horizontal and vertical pair can.
Math Dictionary / Perpendicular Lines
Perpendicular Lines
Perpendicular lines intersect to form right angles.
GeometryGrade 4Grade 5Grade 6Grade 7Grade 8Algebra 1GEDSATACT
What it means
Their intersection makes a 90-degree angle.
Also called: right-angle lines
Examples
| The x-axis and y-axis are perpendicular |
| A vertical wall and horizontal floor can be perpendicular |
| Perpendicular lines meet at 90 degrees |
Common mistake
Intersecting lines are not always perpendicular; they must form right angles.
Try one
Question: What angle do perpendicular lines form?
Show answer
90 degrees.