quadrant Definition

quadrant
noun

1a. geom.
A quarter of the circumference of a circle;
1b. geom.
A plane figure (see plane² adj 3) that is a quarter of a circle, ie an area bounded by two perpendicular radii and the arc between them;
1c. geom.
A quarter of a sphere, ie a section cut by two planes that intersect at right angles at the centre.
2. Any device or mechanical part in the shape of a 90° arc.
3. An instrument that was formerly used in astronomy and navigation and which consists of a graduated 90° arc allowing angular measurements, eg of the stars, to be taken and altitude calculated.

Derivative: quadrantal
adj

Etymology: 14c: from Latin quadrans, quadrantis a fourth part.