lens

noun

• 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).
• the light-gathering device of a camera, typically containing a group of compound lenses.
• Physics an object or device that focuses or otherwise modifies the direction of movement of light, sound, electrons, etc..
• Anatomyshort for crystalline lens.
• short for contact lens.