- Geometry. a plane figure bounded by two radii and the included arc of a circle.
- a mathematical instrument consisting of two flat rulers hinged together at one end and bearing various scales.
- Machinery. a device used in connection with an index plate, consisting of two arms rotating about the center of the plate and set to indicate the angle through which the work is indexed.
- Military. a designated defense area, usually in a combat zone, within which a particular military unit operates and for which it is responsible.
- Astronomy. an instrument shaped like a sector of a circle, having a variable central angle and sights along the two straight sides, for measuring the angular distance between two celestial bodies.
- a distinct part, especially of society or of a nation’s economy: the housing sector; the educational sector.
- a section or zone, as of a city.
- Computers. a portion of a larger block of storage, as 1/128 of a track or disk.
verb (used with object)
- to divide into sectors.
- a part or subdivision, esp of a society or an economythe private sector
- geometry either portion of a circle included between two radii and an arc. Area: 1/2 r ²θ, where r is the radius and θ is the central angle subtended by the arc (in radians)
- a measuring instrument consisting of two graduated arms hinged at one end
- a part or subdivision of an area of military operations
- computing the smallest addressable portion of the track on a magnetic tape, disk, or drum store
n.1560s, “section of a circle between two radii,” from Late Latin sector “section of a circle,” in classical Latin “a cutter, one who cuts,” from sectus, past participle of secare “to cut” (see section (n.)). Translated Greek tomeus in Latin editions of Archimedes. Meaning “area, division” appeared 1920, generalized from military sense (1916) of “part of a front,” based on a circle centered on a headquarters. As a verb from 1884. Related: Sectoral; sectorial.
- The part of a circle bounded by two radii and the arc between them.