What Is the X-Axis?

What Is the X-Axis?

The x-axis is the horizontal axis on a graph.

The image below shows what we mean by the x-axis:

Note: Only part of the x-axis is shown. It can extend forever to the left and right.

How to Use the X-Axis

Imagine you wanted to describe the position of a point on a graph. You would need to know how far across a point is and how far up a point is.

The x-axis lets us measure how far across a point is.

The x-axis is labelled with numbers (0, 1, 2, 3...) so you can measure how far across the point is. This gives the x-coordinate of a point, using Cartesian coordinates.


What is the x-coordinate of the point below?



See how far along the x-axis the point is.

It can help to draw a line (in your minds eye or otherwise) from the point, straight down to the x-axis.


We can see that the point is 2 units along the x-axis. The point has a x coordinate of 2.

The X-Axis Goes On Forever, Left and Right

In the images above, the x-axis starts at 0 and goes on to 5.

This can give the wrong impression. In fact, the x-axis can continue going right (past 100, past 1000, in fact forever).

The x-axis also goes to the left of 0. It is labelled -1, -2, -3. It can also extend forever to the left.

In practice, only draw the parts of the x-axis you need to show.

The X-Axis as a Number Line

The x-axis is a number line that extends horizontally.

The Equation of the X-Axis

The equation of the x-axis is:

It is an equation of a line.

This equation is true because the x-axis crosses the y-axis when y = 0. The y-coordinate of all points on the x-axis are 0.

See Also

What is the x-coordinate? What is a number line? What are Cartesian coordinates? What is an equation?