sector

American  

[sek-ter] / ˈsɛk tər /

noun

1. Geometry. a plane figure bounded by two radii and the included arc of a circle.

2. a distinct part, especially of society or of a nation's economy.

   the housing sector; the educational sector.

3. a section or zone, as of a city.

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. a mathematical instrument consisting of two flat rulers hinged together at one end and bearing various scales.

6. 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.

7. 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.

8. Computers. a portion of a larger block of storage, as 1/128 of a track or disk.

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verb (used with object)

1. to divide into sectors.

sector British  

/ ˈsɛktə /

noun

1. a part or subdivision, esp of a society or an economy

   the 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

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sector Scientific  

/ sĕk′tər /

1. The part of a circle bounded by two radii and the arc between them.

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Other Word Forms

• sectoral
  adjective
• subsector
  noun

Etymology

Origin of sector

First recorded in 1560–70; from Late Latin, from Latin: “cutter,” from sec(āre) “to cut, divide” + -tor -tor

Explanation

Sector sounds like section, doesn't it? That's a good way to remember that a sector is a specific part of society or the economy, made up of similar elements — like the health care sector or the education sector. Our most common use of the word sector refers to a society’s divisions. For example, our economy is divided into the private sector (privately-owned interests) and the public sector (government). Other than that, the word also has many technical applications in math and science. From the Latin verb secare, "to cut," sector was applied long ago to math as a section of a circle, which carried through to military language as "a circle around a headquarters."

Example Sentences

Amid a chorus of concern that AI firms have been overvalued and the sector could be a bubble about to burst, the trial may have bought the industry more time.

From BBC • May 19, 2026

Tech journalist and podcaster Kara Swisher told BBC Radio 4's Today programme that the case has not done much good for the public perception of the AI sector.

From BBC • May 19, 2026

Despite significant advances by the Magnificent Seven stocks and the semiconductor sector since the start of the second quarter, action in the S&P 500 is signaling tech rally concerns.

From Barron's • May 18, 2026

Before AI, most transformative technology came out of the public sector or public-private collaboration: the Manhattan Project, the Defense Advanced Research Projects Agency, the National Science Foundation.

From The Wall Street Journal • May 18, 2026

On Main Street, in stores, in factories and offices, in every sector, black and white mixed all day as a matter of course.

From "The Underground Railroad: A Novel" by Colson Whitehead

Related Words

• district
• part
• region
• zone