Definition of lens:

• biconvex transparent body situated behind the iris in the eye; it focuses light waves on the retina
• electronic equipment that uses a magnetic or electric field in order to focus a beam of electrons
• a transparent optical device used to converge or diverge transmitted light and to form images
• ( metaphor) a channel through which something can be seen or understood; " the writer is the lens through which history can be seen"
• 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.
• A piece of glass or other transparent substance, with one or two curved surfaces, fitted for changing the direction of rays of light; a body in the eyes of animais whose purpose is to bring the rays of light to a point on the sensitive membrane within the eye; the crystalline humor of the eye.
• A piece of glass, quartz, or other transparent substance with one or both surfaces curved, either concave or convex; used for acting upon the rays of light in the way of convergence or dispersal.
• A small circular sheet of transparent glass, used to refract rays of light.
• ( optics) A piece of glass or other transparent substance with one or both sides convex, so called from its likeness to a lentil seed: the crystalline humor of the eye.
• Glass with curved surfaces, which converges or diverges rays of light.
• A curved piece of glass by which rays of light may be made to converge or to diverge.
• In optical instruments, a piece of glass of a convex, concave, or other shape, for changing the direction of rays of light, and thus magnifying or diminishing objects.
• A transparent part of the eye which focusses rays of light on the retina; the crystalline lens; the modified portion of the cornea in front of each element of a compound eye.
• [ Latin] A transparent part of eye, which focuses rays of light on retina; crystalline lens; modified portion of cornea in front of each element of a compound eye.
• A piece of glass or other transparent substance, so shaped that rays of light passing through it are made to change their direction, and to magnify or diminish objects at a certain distance; the crystalline humour of the eye.

Usage examples for lens

1. Second, a pair of eye- glasses fitted with a powerful microscopic lens, able to distinguish good from evil.  The Desire of the Moth; and The Come On by Eugene Manlove Rhodes

2. They were dressed like Tako save that they each had a great round lens like a monocle on the left eye, with dangling wires from it leading to dials fastened to the belt.  The White Invaders by Raymond King Cummings

3. It will be observed that in the last cut the image produced by the lens is curved.  American Handbook of the Daguerrotype by Samuel D. Humphrey

4. On the freshly split surface of one piece we see scattered a number of small darker brown fragments; an examination with a pocket lens clearly shows that these are little bits of leaves and stems, with here and there a more perfect specimen.  Sea-Weeds, Shells and Fossils by Peter Gray B. B. Woodward