noun

1. 1. a piece of glass, or other transparent substance, with two curved surfaces, or one plane and one curved, regularly bringing together or spreading rays of light passing through it: a lens or combination of lenses is used in optical instruments, eyeglasses, etc. to form an image
   2. a combination of two or more such pieces
2. any of various devices used to focus microwaves, electrons, or sound waves
3. Anat. a transparent, biconvex body situated between the iris and the vitreous humor of the eye: it focuses upon the retina light rays entering the pupil

Etymology: L, lentil: from the resemblance to the shape of a lentil

transitive verb

1. to photograph
2. to make a film of