What is the name of the horizontal number line in a coordinate plane?

The horizontal number line in a coordinate plane is called the X-axis. This axis is used to represent the independent variable in a Cartesian coordinate system. In two-dimensional space, the X-axis runs from left to right and typically intersects the vertical Y-axis at the origin, which is the point at coordinates (0, 0). Each point on the X-axis corresponds to a specific value, making it essential for graphing equations and understanding relationships between variables in mathematics. Understanding the role of the X-axis is crucial for anyone studying coordinate geometry, as it helps in plotting points and visualizing functions.