The Collaborative International Dictionary of English v.0.48:

Lens \Lens\ (l[e^]nz), n.; pl. Lenses (-[e^]z). [L. lens a
   lentil. So named from the resemblance in shape of a double
   convex lens to the seed of a lentil. Cf. Lentil.] (Opt.)
   A piece of glass, or other transparent substance, ground with
   two opposite regular surfaces, either both curved, or one
   curved and the other plane, and commonly used, either singly
   or combined, in optical instruments, for changing the
   direction of rays of light, and thus magnifying objects, or
   otherwise modifying vision. In practice, the curved surfaces
   are usually spherical, though rarely cylindrical, or of some
   other figure.
   [1913 Webster] Lenses
   [1913 Webster]

   Note: Of spherical lenses, there are six varieties, as shown
         in section in the figures herewith given: viz., a
         plano-concave; b double-concave; c plano-convex; d
         double-convex; e converging concavo-convex, or
         converging meniscus; f diverging concavo-convex, or
         diverging meniscus.
         [1913 Webster]

   Crossed lens (Opt.), a double-convex lens with one radius
      equal to six times the other.

   Crystalline lens. (Anat.) See Eye.

   Fresnel lens (Opt.), a compound lens formed by placing
      around a central convex lens rings of glass so curved as
      to have the same focus; used, especially in lighthouses,
      for concentrating light in a particular direction; -- so
      called from the inventor.

   Multiplying lens or Multiplying glass (Opt.), a lens one
      side of which is plane and the other convex, but made up
      of a number of plane faces inclined to one another, each
      of which presents a separate image of the object viewed
      through it, so that the object is, as it were, multiplied.


   Polyzonal lens. See Polyzonal.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lens
    n 1: a transparent optical device used to converge or diverge
         transmitted light and to form images [syn: lens, lense,
         lens system]
    2: genus of small erect or climbing herbs with pinnate leaves
       and small inconspicuous white flowers and small flattened
       pods: lentils [syn: Lens, genus Lens]
    3: (metaphor) a channel through which something can be seen or
       understood; "the writer is the lens through which history can
       be seen"
    4: biconvex transparent body situated behind the iris in the
       eye; its role (along with the cornea) is to focuses light on
       the retina [syn: lens, crystalline lens, lens of the
       eye]
    5: electronic equipment that uses a magnetic or electric field
       in order to focus a beam of electrons [syn: lens, electron
       lens]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "lens":
   baby blues, banjo eyes, bright eyes, clear eyes, cornea, eye,
   eyeball, eyelid, goggle eyes, iris, lid, naked eye,
   nictitating membrane, oculus, optic, optic nerve, orb,
   organ of vision, peeper, popeyes, pupil, retina, saucer eyes,
   sclera, starry orbs, unaided eye, visual organ



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

LENS
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