A Sector

1. section
2. zone (designated area).
3. (geometry) part of a circle, extending to the center

4. (computer hardware) fixed-sized unit (traditionally 512 bytes) of sequential data stored on a track of a digital medium (compare to block)
5. (military) an area designated by boundaries within which a unit operates, and for which it is responsible
6. (military) one of the subdivisions of a coastal frontier
7. (science fiction) a fictional region of space designated for navigational or governance purposes.
8. (calculation) an instrument consisting of two rulers of equal length joined by a hinge.
9. a field of economic activity
10. (engineering) A toothed gear whose face is the arc of a circle.
11. (motor racing) A fixed, continuous section of the track, such that sectors do not overlap but all sectors make up the whole track.