An axis is a straight line that serves as a reference for measuring or organizing data in various fields, such as mathematics and science. In a two-dimensional space, like a graph, there are typically two axes: the horizontal axis, known as the x-axis, and the vertical axis, known as the y-axis. These axes help to plot points, visualize relationships, and analyze trends. In three-dimensional space, a third axis, called the z-axis, is added to represent depth. Axes are essential in coordinate systems, allowing for precise location and movement in both physical and abstract contexts. They are fundamental in disciplines like geometry, physics, and engineering.