The Collaborative International Dictionary of English v.0.48:

Sector \Sec"tor\, n. [L., properly, a cutter, fr. secare,
   sectum, to cut: cf. F. secteur. See Section.]
   1. (Geom.) A part of a circle comprehended between two radii
      and the included arc.
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   2. A mathematical instrument, consisting of two rulers
      connected at one end by a joint, each arm marked with
      several scales, as of equal parts, chords, sines,
      tangents, etc., one scale of each kind on each arm, and
      all on lines radiating from the common center of motion.
      The sector is used for plotting, etc., to any scale.
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   3. An astronomical instrument, the limb of which embraces a
      small portion only of a circle, used for measuring
      differences of declination too great for the compass of a
      micrometer. When it is used for measuring zenith distances
      of stars, it is called a zenith sector.
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   Dip sector, an instrument used for measuring the dip of the
      horizon.

   Sector of a sphere, or Spherical sector, the solid
      generated by the revolution of the sector of a circle
      about one of its radii, or, more rarely, about any
      straight line drawn in the plane of the sector through its
      vertex.
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The Collaborative International Dictionary of English v.0.48:

Spherical \Spher"ic*al\, Spheric \Spher"ic\, a. [L. sphaericus,
   Gr. ???: cf. F. sph['e]rique.]
   1. Having the form of a sphere; like a sphere; globular;
      orbicular; as, a spherical body.
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   2. Of or pertaining to a sphere.
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   3. Of or pertaining to the heavenly orbs, or to the sphere or
      spheres in which, according to ancient astronomy and
      astrology, they were set.
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            Knaves, thieves, and treachers by spherical
            predominance.                         --Shak.
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            Though the stars were suns, and overburned
            Their spheric limitations.            --Mrs.
                                                  Browning.
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   Spherical angle, Spherical coordinate, Spherical
   excess, etc. See under Angle, Coordinate, etc.

   Spherical geometry, that branch of geometry which treats of
      spherical magnitudes; the doctrine of the sphere,
      especially of the circles described on its surface.

   Spherical harmonic analysis. See under Harmonic, a.

   Spherical lune,portion of the surface of a sphere included
      between two great semicircles having a common diameter.

   Spherical opening, the magnitude of a solid angle. It is
      measured by the portion within the solid angle of the
      surface of any sphere whose center is the angular point.


   Spherical polygon,portion of the surface of a sphere
      bounded by the arcs of three or more great circles.

   Spherical projection, the projection of the circles of the
      sphere upon a plane. See Projection.

   Spherical sector. See under Sector.

   Spherical segment, the segment of a sphere. See under
      Segment.

   Spherical triangle,re on the surface of a sphere, bounded
      by the arcs of three great circles which intersect each
      other.

   Spherical trigonometry. See Trigonometry.
      [1913 Webster] -- Spher"ic*al*ly, adv. --
      Spher"ic*al*ness, n.
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