octant
/ˈɒktənt/noun
1- an arc of a circle equal to one eighth of its circumference, or the area enclosed by such an arc with two radii of the circle八分弧; 八分圆。
1.1
- each of eight parts into which a space or solid body is divided by three planes which intersect (especially at right angles) at a single point（由三个平面正交分割而成的）卦限八分区之一。
1.2
- an obsolete instrument in the form of a graduated eighth of a circle, used in astronomy and navigation八分仪。
词源
late 17th cent.: from Latin octans, octant- 'half-quadrant', from octo 'eight'.