octante

Octante, or octant in English, is a term used to denote one-eighth of a whole. The form octante appears in several Romance languages to refer to the same division and is used in mathematics, navigation, and geometry to describe an eighth-part portion or a related instrument.

In nautical navigation, the octant is a historical instrument used to measure the altitude of celestial objects above the horizon. It employs a 45-degree arc, or one-eighth of a circle, and a system of mirrors to create a double reflection. This design enables readings of angles up to ninety degrees on a graduated scale. The octant was developed independently by John Hadley and Thomas Godfrey in the 1730s and became widely used for celestial navigation until the sextant largely supplanted it in the 19th century.

In geometry, an octant is one of eight regions into which three-dimensional space is divided by the three coordinate planes. The most common example is the first octant, defined by x ≥ 0, y ≥ 0, and z ≥ 0. Octants are used in three-dimensional analytic geometry, calculus, and related fields to describe volumes, integrals, and probability constrained to a specific portion of space.

The term’s usage varies by context, but in general, octante/oсtant denotes either an eighth division of a whole or a device or region associated with that division.