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The Collaborative International Dictionary of English v.0.48 (gcide)

Phosphorus \Phos"phor*us\ (f[o^]s"f[o^]r*[u^]s), n.; pl.
{Phosphori} (f[o^]s"f[o^]r*[imac]). [L., the morning star,
Gr. fwsfo`ros, lit., light bringer; fw^s light fe`rein to
bring.]
1. The morning star; Phosphor.
[1913 Webster]

2. (Chem.) A poisonous nonmetallic element of the nitrogen
group, obtained as a white, or yellowish, translucent waxy
substance, having a characteristic disagreeable smell;
this waxy allotropic form is also called {yellow
phosphorus}, to distinguish it from another allotropic
form, {red phosphorus}. 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 combined, 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. It is an essential component of the
genetic material of all living organisms. The molecule
contains four atoms. Symbol P. Atomic weight 31.0.
[1913 Webster]

3. (Chem.) Hence, any substance which shines in the dark like
phosphorus, as certain phosphorescent bodies.
[1913 Webster]

{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 phosphorus}, 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.

{yellow phosphorus} (Chem.), the waxy yellow allotropic form
of elemental phosphorus. See also {phosphorus}[2].
[1913 Webster PJC]