On a graph, what is the vertical axis known as?

The vertical axis on a graph is known as the Y-axis. This convention is established in Cartesian coordinate systems, where the two axes are typically labeled as the X-axis for the horizontal component and the Y-axis for the vertical component. The Y-axis represents the dependent variable, which changes in response to the independent variable plotted along the X-axis. Understanding this distinction is crucial for interpreting graphs correctly, as it helps identify the relationship between the two variables being analyzed. The other options, such as the X-axis, Z-axis, and Origin, refer to different aspects of graphing: the X-axis is horizontal, the Z-axis is used in three-dimensional graphs, and the Origin is the point where the X and Y axes intersect.