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The x-axis and y-axis, collectively known as the axes, form the basis of the xy-plane. Essentially, these are a pair of number lines set at right angles, as shown in Figure 2-2. The arrows indicate that each axis extends infinitely in both directions. Thus, the xy-plane also extends infinitely in every direction.

FIGURE 2-2: The xy-plane.

These two axes divide the xy-plane into four regions called quadrants that extend infinitely outward from the axes.

The intersection point of the two axes is called the origin.