/lenz/
Noun, pl. lenses
(Anatomy)
1. A transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina. (wikipedia.org)
2. The transparent crystalline structure in the eye. (wiktionary.org)
(Geometory)
1. A convex shape bounded by two circular arcs, joined at their endpoints, the corresponding concave shape being a lune. (wiktionary.org)
(Biology)
1. A genus of the legume family; its bean. (wiktionary.org)
2. Genus of small erect or climbing herbs with pinnate leaves and small inconspicuous white flowers and small flattened pods: lentils. (wordnetweb.princeton.edu)
(Other definitions)
1. An object, usually made of glass, that focuses or defocuses the light that passes through it. (wiktionary.org)
2. A device which focuses or defocuses electron beams. (wiktionary.org)
3. A piece of glass or other transparent substance with curved sides for concentrating or dispersing light rays, used singly (as in a magnifying glass) or with other lenses (as in a telescope). (Google Dictionary)
4. The light-gathering device of a camera, typically containing a group of compound lenses. (Google Dictionary)
5. An object or device that focuses or otherwise modifies the direction of movement of light, sound, electrons, etc. (Google Dictionary)
6. A transparent optical element, so constructed that it serves to change the degree of convergence or divergence of the transmitted rays. (biology-online.org)
Word origin: From Latin lens (genitive lentis) “lentil,” on analogy of the double-convex shape