Definition: A nonmetallic chemical element, atomic no. 15, atomic wt. 30.973762, occurring extensively in nature, always in compounds such as phosphates and phosphites and as the phosphate in every living cell; the elemental form is extremely poisonous, causing intense inflammation and fatty degeneration; repeated inhalation of phosphorus fumes may cause necrosis of the jaw (phosphonecrosis); the approximate fatal dose is 50–100 mg.
[G. phosphoros, fr. phōs, light, + phoros, bearing]