\Phos"phor*us\, n.; pl. {Phosphori}. [L., the morning
star, Gr. ?, lit., light bringer; ? light + ? to bring.]
1. The morning star; Phosphor.
2. (Chem.) A poisonous nonmetallic element of the nitrogen
   group, obtained as a white, or yellowish, translucent waxy
   substance, having a characteristic disagreeable smell. It
   is very active chemically, must be preserved under water,
   and unites with oxygen even at ordinary temperatures,
   giving a faint glow, -- whence its name. It always occurs
   compined, usually in phosphates, as in the mineral
   apatite, in bones, etc. It is used in the composition on
   the tips of friction matches, and for many other purposes.
   The molecule contains four atoms. Symbol P. Atomic weight
   31.0.
3. (Chem.) Hence, any substance which shines in the dark like
   phosphorus, as certain phosphorescent bodies.
{Bologna phosphorus} (Chem.), sulphide of barium, which
   shines in the dark after exposure to light; -- so called
   because this property was discovered by a resident of
   Bologna. The term is sometimes applied to other compounds
   having similar properties.
{Metallic phosphorus} (Chem.), an allotropic modification of
   phosphorus, obtained as a gray metallic crystalline
   substance, having very inert chemical properties. It is
   obtained by heating ordinary phosphorus in a closed vessel
   at a high temperature.
{Phosphorus disease} (Med.), a disease common among workers
   in phosphorus, giving rise to necrosis of the jawbone, and
   other symptoms.
{Red, or Amorphous}, {phosphorus} (Chem.), an allotropic
   modification of phosphorus, obtained as a dark red powder
   by heating ordinary phosphorus in closed vessels. It is
   not poisonous, is not phosphorescent, and is only
   moderately active chemically. It is valuable as a chemical
   reagent, and is used in the composition of the friction
   surface on which safety matches are ignited.
{Solar phosphori} (Chem.), phosphorescent substances which
   shine in the dark after exposure to the sunlight or other
   intense light.