Definition of: quadrant

(kwod′rənt) noun
1. The quarter of a circle, or of its circumference.
2. An instrument having a graduated arc of 90°, with a movable radius for measuring angles on it; especially, a nautical instrument for measuring the altitude of the sun.
3. Geom. In a Cartesian coordinate system, any of the four sections formed by the intersection of the axes: beginning with the upper right-hand quadrant where the ordinate and abscissa are positive, they are called the first, second, third, and fourth quadrants, in counter-clockwise order. See illustration on page 1030.
4. A device or machine-part having the shape of, or suggesting the quadrant of a circle. [<L quadrans, -antis a fourth part <quattuor four]
—quad·ran·tal (kwod·ran′təl) adjective
CARTESIAN QUADRANT