Which axis is represented as vertical in a graph?

In a standard Cartesian coordinate system, the vertical axis is designated as the y-axis. This is a fundamental aspect of graphing where the x-axis typically runs horizontally and represents the independent variable, while the y-axis runs vertically and represents the dependent variable. The vertical orientation of the y-axis allows it to display values that trend upward or downward according to the data being analyzed.

In three-dimensional graphs, the z-axis adds depth but is also oriented vertically in a manner that is perpendicular to both the x-axis and y-axis. However, in the context of standard two-dimensional graphs, it is the y-axis that is consistently identified as vertical. The r-axis, often used in polar coordinates, is not a typical representation in standard Cartesian graphs, thus making the y-axis the most recognizable vertical representation.