At right angles to the horizon.
In math, vertical means straight up and down. An easy way to remember this is to think of a vertical line as a flagpole or a tree – it goes (or grows, rather) from bottom to top.
We describe vertical lines as being perpendicular to horizontal lines. That means they meet at a right angle (90°).
Here are a few examples of vertical in math:
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On a graph, the y-axis is vertical because it runs up and down.
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In geometry, we use vertical lines to help form right angles and describe shapes like rectangles.
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When graphing points or drawing shapes, vertical lines help us understand position and direction.
When Do Students Learn About Vertical?
Students begin exploring vertical and horizontal directions early on when learning about shapes and basic geometry.
Grades 1–2 – Introduction to Vertical and Horizontal
Students learn to recognize vertical lines and objects and compare them to horizontal lines in pictures and objects around them.
Grades 3–5 – Using Vertical in Geometry and Graphing
Students use the idea of vertical to draw and identify perpendicular and parallel lines and to understand vertical and horizontal axes when graphing points on the coordinate plane. These skills help them recognize how vertical lines show direction, position, and right angles in geometry and graphs.
Grades 6+ – Using Vertical in Coordinate Geometry
Students use the idea of vertical to describe vertical lines (undefined slope). They also explore how vertical and horizontal lines model perpendicular and parallel relationships.
