What does the y-axis represent on a coordinate plane?

The y-axis represents the vertical number line on a coordinate plane. In a standard Cartesian coordinate system, the y-axis is oriented vertically and is used to display the values of the dependent variable in a function or relationship plotted on the graph. Each point on the plane is defined by an ordered pair (x, y), where the first number (x) indicates the horizontal position on the x-axis and the second number (y) indicates the vertical position on the y-axis. Understanding this helps in interpreting and analyzing data represented in the coordinate system, such as identifying trends, plotting equations, or understanding spatial relationships.

Other representations, such as the horizontal number line or midpoints, do not accurately describe the role of the y-axis in the coordinate plane, nor does the concept of a maximum limit of values pertain specifically to the y-axis itself.