Axis

>

Alternatively referred to as a coordinate axis an axis is an imaginary line that crosses through a point. In a 3-D environment, there are three axis's as shown in the illustration. In this illustration, you can see an X, Y, and Z-axis, the X-axis is the horizontal axis, the Y-axis is the vertical axis, and the Z-axis is the depth axis.
An axis or chart axis is the description of values displayed on the side of a chart that describe the values of what is being displayed.
Also see: Absolute coordinates, X-axis, Y-axis, Z-axis