D defs.my
Entry 2 senses Webster, 1913

Vergency

· Ver·gen·cy · IPA
01 n. The act of verging or approaching; tendency; approach.
  1. 1.
    The act of verging or approaching; tendency; approach.[R.]
  2. 2.
    The reciprocal of the focal distance of a lens, used as measure of the divergence or convergence of a pencil of rays.(Opt.) [R.]