2. a combination of two or more such pieces

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 to form an image:  for kinds of lenses, see illustrations following concave and convex.

jawbone, v.t. and v.i. ; jawboned, pt., pp. ; jawboning, ppr.

How Heavenly Bodies