The x-axis is the horizontal line on a graph that usually shows what you're measuring or comparing. Picture a graph as having two number lines that cross each other: the x-axis runs left to right, and the y-axis runs up and down.

If you're graphing how much money you saved each month, the x-axis might show the months (January, February, March) while the y-axis shows the dollar amounts. If you're tracking plant growth over time, the x-axis typically represents days or weeks, and the y-axis shows height. The x-axis is where you mark your independent variable, which is the thing you control or the thing that changes naturally, like time passing.

On a coordinate plane, any point can be located using an x-coordinate (its position along the x-axis) and a y-coordinate (its position along the y-axis). The point (3, 5) means go three units along the x-axis, then five units up. The x-axis and y-axis meet at a point called the origin, marked (0, 0).