Lens (hydrology) definition

(1) A transparent optical device used to converge or diverge transmitted light and to form images

(2) Electronic equipment that uses a magnetic or electric field in order to focus a beam of electrons

(3) Biconvex transparent body situated behind the iris in the eye; it focuses light waves on the retina

(4) (metaphor) a channel through which something can be seen or understood

"The writer is the lens through which history can be seen"

(5) Genus of small erect or climbing herbs with pinnate leaves and small inconspicuous white flowers and small flattened pods: lentils