What is the function of the y-axis in coordinate geometry?

The function of the y-axis in coordinate geometry is to represent the vertical axis of the Cartesian coordinate system. In this system, points are plotted using pairs of numerical coordinates, typically written as (x, y), where 'x' indicates the horizontal position and 'y' indicates the vertical position. The y-axis allows for the visualization of how a variable changes in relation to another variable represented by the x-axis. This is fundamental in understanding relationships in various mathematical functions and contexts, such as linear equations, quadratic functions, and other graphical representations where the vertical dimension is significant for interpreting data.