The Cartesian plane is divided into four **quadrants**. These are numbered from I through IV, starting with the upper right and going around counterclockwise. (For some reason everybody uses roman numerals for this).

In Quadrant I, both the *x*– and *y*-coordinates are positive; in Quadrant II, the *x*-coordinate is negative, but the *y*-coordinate is positive; in Quadrant III both are negative; and in Quadrant IV *x* is positive but *y* is negative.

Points which lie on an axis (i.e., which have at least one coordinate equal to 0) are said not to be in any quadrant. Coordinates of the form (*x*, 0) lie on the horizontal *x*-axis, and coordinates of the form (0, *y*) lie on the vertical *y*-axis.