octant

American  

[ok-tuhnt] / ˈɒk tənt /

noun

1. the eighth part of a circle.

2. Mathematics. any of the eight parts into which three mutually perpendicular planes divide space.

3. an instrument having an arc of 24°, used by navigators for measuring angles up to 90°.

4. the position of one heavenly body when 45° distant from another.

5. Astronomy. Octant, the constellation Octans.

---

octant British  

/ ˈɒktənt /

noun

1. maths

   1. any of the eight parts into which the three planes containing the Cartesian coordinate axes divide space

   2. an eighth part of a circle

2. astronomy the position of a celestial body when it is at an angular distance of 45° from another body

3. an instrument used for measuring angles, similar to a sextant but having a graduated arc of 45°

---

Other Word Forms

• octantal adjective

Etymology

Origin of octant

First recorded in 1680–90; from Latin octant- (stem of octāns ); Octans

Example Sentences

The solid E bounded by z = 10 − 2x − y and situated in the first octant is given in the following figure.

From Textbooks • Mar. 30, 2016

Find the maximum volume of a rectangular box with three faces in the coordinate planes and a vertex in the first octant on the plane x + y + z = 1.

From Textbooks • Mar. 30, 2016

Find the volume of the solid situated in the first octant and bounded by the planes x + 2y = 1, x = 0, y = 0, z = 4, and z = 0.

From Textbooks • Mar. 30, 2016

Find the volume of the solid situated in the first octant and determined by the planes z = 2, z = 0, x + y = 1, x = 0, and y = 0.

From Textbooks • Mar. 30, 2016

Excluded, of course, are those instruments normally made of wood, such as the octant and the mariners quadrant.

From Early American Scientific Instruments and Their Makers by Bedini, Silvio A.