• A nonmetallic chemical element whose atomic number is 15. It has three allotropic forms, one consists of white or colorless crystals, another of a black solid resembling graphite, and the third is a red to violet powder. White phosphorous is poisonous, ignites spontaneously in air, and is phosphorescent. Red phosphorous is more stable and is used in semiconductors and electroluminescent coatings. Black phosphorous is electrically conductive. Phosphorus has about 20 known isotopes, of which one is stable. Its chemical symbol is P.
  • chemical symbolP


  • An essential inorganic element necessary for health. Usually in the form of phosphates which are essential for cellular processes as well as for the construction of bones and teeth.


  • noun a toxic chemical element which is present in very small quantities in bones and nerve tissue. It causes burns if it touches the skin, and can poison if swallowed.

Origin & History of “phosphorus”

Etymologically, phosphorus means ‘bringing light’. The word comes via Latin phōsphorus from Greek phōsphóros, a compound adjective formed from phōs ‘light’ and the suffix -phóros ‘carrying’ (a relative of English bear), which was used as an epithet for the planet Venus as it appears at dawn. It was also applied to any substance that glowed, and in the mid 17th century it was taken up as the term for the newly isolated element phosphorus, which catches fire when exposed to the air. Phosphate (18th c.) was borrowed from French phosphat, a derivative of phosphore ‘phosphorus’.