1. Geometry. a plane figure bounded by two radii and the included arc of a circle.
  2. a mathematical instrument consisting of two flat rulers hinged together at one end and bearing various scales.
  3. 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.
  4. Military. a designated defense area, usually in a combat zone, within which a particular military unit operates and for which it is responsible.
  5. 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.
  6. a distinct part, especially of society or of a nation's economy: the housing sector; the educational sector.
  7. a section or zone, as of a city.
  8. Computers. a portion of a larger block of storage, as 1/128 of a track or disk.
verb (used with object)
  1. to divide into sectors.

Origin of sector

1560–70; < Late Latin: sector, Latin: cutter, equivalent to of sec(āre) to cut + -tor -tor
Related formssec·tor·al, adjectivesub·sec·tor, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for sub-sector

Historical Examples of sub-sector

  • We only stayed here twenty-four hours and then went into the front line, "Cambrin Right" sub-sector.

British Dictionary definitions for sub-sector


  1. a part or subdivision, esp of a society or an economythe private sector
  2. 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)
  3. a measuring instrument consisting of two graduated arms hinged at one end
  4. a part or subdivision of an area of military operations
  5. computing the smallest addressable portion of the track on a magnetic tape, disk, or drum store
Derived Formssectoral, adjective

Word Origin for sector

C16: from Late Latin: sector, from Latin: a cutter, from secāre to cut
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for sub-sector



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.

Online Etymology Dictionary, © 2010 Douglas Harper

sub-sector in Science


  1. The part of a circle bounded by two radii and the arc between them.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.