phosphorus

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A highly reactive, poisonous, nonmetallic element occurring naturally in phosphates, especially apatite, and existing in three allotropic forms, white (or sometimes yellow), red, and black (or violet). An essential constituent of protoplasm, it is used in safety matches, pyrotechnics, incendiary shells, and fertilizers and to protect metal surfaces from corrosion. Atomic number 15; atomic weight 30.9738; melting point (white) 44.15°C; boiling point 280.5°C; specific gravity (white) 1.82, (red) 2.16, (black) 2.25 to 2.69; valence 3, 4, 5. cross-reference: Periodic Table.
• noun A phosphorescent substance.

from The Century Dictionary.

• noun [With a pl. phosphori (-rī).] In early use, a substance which emits light otherwise than as the result of ordinary combustion.
• noun [capitalized] The morning star; Phosphor.
• noun Chemical symbol, P; atomic weight, 31; specific gravity, 1.826. A solid non-metallic combustible substance, hitherto undecomposed, not found by itself in nature, but occurring chiefly in combination with oxygen, calcium, and magnesium.
• noun A small bottle containing 12 grains of phosphorus melted in half an ounce of olive-oil. On being uncorked in the dark this solution emits light enough to illuminate the dial of a watch, and it will retain this property for several years if not too frequently used.

from the GNU version of the Collaborative International Dictionary of English.

• noun The morning star; Phosphor.
• noun (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. The molecule contains four atoms. Symbol P. Atomic weight 31.0.
• noun (Chem.) Hence, any substance which shines in the dark like phosphorus, as certain phosphorescent bodies.
• noun (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.
• noun (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.
• noun (Med.) a disease common among workers in phosphorus, giving rise to necrosis of the jawbone, and other symptoms.
• noun (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.
• noun (Chem.) phosphorescent substances which shine in the dark after exposure to the sunlight or other intense light.
• noun (Chem.) the waxy yellow allotropic form of elemental phosphorus. See also phosphorus{2}.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry a chemical element (symbol P) with an atomic number of 15, that exists in several allotropic forms.
• noun obsolete any substance exhibiting phosphorescence; a phosphor

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a planet (usually Venus) seen just before sunrise in the eastern sky
• noun a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms