n.1 a distinct part or branch of an enterprise, or of society, the economy, etc.
2 Mil. a subdivision of an area for military operations, controlled by one commander or headquarters.
3 the plane figure enclosed by two radii of a circle, ellipse, etc., and the arc between them.
4 a mathematical instrument consisting of two arms hinged at one end and marked with sines, tangents, etc., for making diagrams etc.
Derivatives:
sectoral adj.
Etymology: LL, techn. use of L sector cutter (as SECTION)