Phosphor /(fŏs"fôr or fŏs"fŏr)/

Phos·phor

Phosphor

n.
  1. Phosphorus. [Obs.]
  2. The planet Venus, when appearing as the morning star; Lucifer. [Poetic and Rare]
  3. A phosphorescent substance. [archaic]
  4. A substance capable of exhibiting luminescence. This term is now most commonly used to refer to substances used in fluorescent lights, image intensifiers, or cathode-ray tubes (CRT's), which luminesce when excited by ultraviolet radiation or an electron beam. In color CRT's, three different phosphors, each giving different colors when excited, are used.