In the rectangular coordinate system, the vertical number line is called the y-axis. This axis runs up and down on a graph and is perpendicular to the horizontal number line, known as the x-axis.
The origin point, where the two axes intersect, is designated as (0,0). The y-axis allows us to represent values on a vertical scale, such as height, temperature, or any other variable that can be plotted along that dimension. Points on the graph are represented in the form of ordered pairs (x, y), where the ‘x’ value indicates the position along the x-axis and the ‘y’ value indicates the position along the y-axis. Understanding the role of the y-axis is fundamental to reading and creating graphs in the rectangular coordinate system.