lens in WordNet English dictionary

1. biconvex transparent body situated behind the iris in the eye; its role (along with the cornea) is to focuses light on the retina
   lens  crystalline lens  lens of the eye 
   
2. electronic equipment that uses a magnetic or electric field in order to focus a beam of electrons
   lens  electron lens 
   
3. a transparent optical device used to converge or diverge transmitted light and to form images
   lens  lense  lens system 
   
4. (metaphor) a channel through which something can be seen or understood
   "the writer is the lens through which history can be seen"
   lens