The Cartesian plane is divided into four quadrants. These are numbered from through , starting with the upper right and going around counterclockwise. (For some reason everybody uses roman numerals for this).
In Quadrant , both the – and -coordinates are positive; in Quadrant , the -coordinate is negative, but the -coordinate is positive; in Quadrant both are negative; and in Quadrant , is positive but is negative.
Points which lie on an axis (i.e., which have at least one coordinate equal to ) are said not to be in any quadrant. Coordinates of the form lie on the horizontal -axis, and coordinates of the form lie on the vertical -axis.