The horizontal axis is labeled x and the vertical axis y. The axes are labeled with numbers. An ordered pair (x,y) specifies the location of a point P on the plane. These two axes form four quadrants. Moving counter clockwise, starting in the upper right quadrant, the quadrants are labeled I, II, III, and IV. In quadrant I, all x- and y-values are positive, in II, x is negative and y positive, in III, all values are negative, and only x is positive in IV. The ordered pair (0,0) represents the origin where the axes intersect.

Fig. 3 - The four quadrants of a Cartesian coordinate system. The arrows on the axes indicate that they extend forever in their respective directions (i.e. infinitely).