lens

1. (optics) An object, usually made of glass, that focuses or defocuses the light that passes through it.Examples: "Not long ago, it was difficult to produce photographs of tiny creatures with every part in focus. That’s because the lenses that are excellent at magnifying tiny subjects produce a narrow depth of field."

2. (geometry) A convex shape bounded by two circular arcs, joined at their endpoints, the corresponding concave shape being a lune.

3. (biology) A genus of the legume family; its bean.

4. (anatomy) The transparent crystalline structure in the eye.Examples: "The single-imaging optic of the mammalian eye offers some distinct visual advantages. Such lenses can take in photons from a wide range of angles, increasing light sensitivity. They also have high spatial resolution, resolving incoming images in minute detail."

5. (earth science) A body of rock, ice, or water shaped like a convex lens.

6. (programming) A construct used in statically-typed functional programming languages to access nested data structures.