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# 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