Which axis is the horizontal line in the coordinate plane?

In the coordinate plane, the horizontal line is represented by the X-axis. This axis is the line that runs from left to right and is used to measure the values of the x-coordinates in a coordinate system. Each point on this axis has a y-coordinate of zero, indicating that it does not move up or down from the origin.

The X-axis is crucial for plotting points, as it helps define the horizontal position of any given coordinate pair. Understanding that the X-axis is oriented horizontally while the Y-axis runs vertically reinforces the basic structure of the Cartesian coordinate system, which allows for easy navigation and plotting of points in mathematics.