Octant vs. Quadrant — What's the Difference?

A 45° arc.

A circular arc of 90°; one fourth of the circumference of a circle.

One eighth of a circle.

The plane area bounded by such an arc and two perpendicular radii.

The area enclosed by two radii at a 45° angle and the intersected arc.

Any of the four areas into which a plane is divided by the reference axes in a Cartesian coordinate system, designated first, second, third, and fourth, counting counterclockwise from the area in which both coordinates are positive.

An instrument based on the principle of the sextant but employing only a 45° angle, used as an aid in navigation.

A machine part or other mechanical device that is shaped like a quarter circle.

(Astronomy) The position of a celestial body when it is separated from another by a 45° angle.

An early instrument for measuring altitude of celestial bodies, consisting of a 90° graduated arc with a movable radius for measuring angles.

One of eight parts into which three-dimensional space is divided by three usually perpendicular coordinate planes.

One of the four sections made by dividing an area with two perpendicular lines.

The eighth part of a circle; an arc of 45 degrees.

(mathematics) One of the four regions of the Cartesian plane bounded by the x-axis and y-axis.

(astrology) The aspect of two planets that are 45°, or one-eighth of a circle, apart.

(geometry) One fourth of a circle or disc; a sector with an angle of 90°.

(geometry) The eighth part of a disc; a sector of 45 degrees; half a quadrant.

(nautical) A measuring device with a graduated arc of 90° used in locating an altitude.

(nautical) An instrument for measuring angles, particularly of elevation.

(college basketball) One of the four categories of team wins and losses, as categorized by strength of schedule.

The eighth part of a circle; an arc of 45 degrees.

(obsolete) A square or quadrangle.

The position or aspect of a heavenly body, as the moon or a planet, when half way between conjunction, or opposition, and quadrature, or distant from another body 45 degrees.

The fourth part; the quarter.

An instrument for measuring angles (generally called a quadrant), having an arc which measures up to 9O°, but being itself the eighth part of a circle. Cf. Sextant.

The quarter of a circle, or of the circumference of a circle, an arc of 90°, or one subtending a right angle at the center.

One of the eight parts into which a space is divided by three coördinate planes.

One of the four parts into which a plane is divided by the coördinate axes. The upper right-hand part is the first quadrant; the upper left-hand part the second; the lower left-hand part the third; and the lower right-hand part the fourth quadrant.

A measuring instrument for measuring angles to a celestial body; similar to a sextant but with 45 degree calibration

An instrument for measuring altitudes, variously constructed and mounted for different specific uses in astronomy, surveying, gunnery, etc., consisting commonly of a graduated arc of 90°, with an index or vernier, and either plain or telescopic sights, and usually having a plumb line or spirit level for fixing the vertical or horizontal direction.

A quarter of the circumference of a circle

A quarter of the circumference of a circle

Any of the four areas into which a plane is divided by two orthogonal coordinate axes

The area enclosed by two perpendicular radii of a circle

A measuring instrument for measuring altitude of heavenly bodies