A phosphor is a substance that exhibits the phenomenon of phosphorescence (sustained glowing without further stimulus).
The chemical element phosphorus (Greek. phosphoros, meaning "light bearer") was discovered by German alchemist Hennig Brand in 1669 through a preparation from urine. Working in Hamburg, Brand attempted to distill salts by evaporating urine, and in the process produced a white material that glowed in the dark. Since that time, the term phosphorescence has been used to describe substances that shine in the dark without burning.
Phosphorus itself is NOT a phosphor; it is highly reactive and gives-off a faint glow upon uniting with oxygen. The glow observed by Brand was actually caused by the very slow burning of the phosphorus, but as he saw no flame nor felt any heat he did not recognize it as burning.
Phosphors are transition metal compounds or rare earth compounds of various types. The most common uses of phosphors are in CRT displays and fluorescent lights.
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