[fos-fer-uh s]

noun, plural phos·pho·ri [fos-fuh-rahy] /ˈfɒs fəˌraɪ/.

Chemistry. a solid, nonmetallic element existing in at least three allotropic forms, one that is yellow, poisonous, flammable, and luminous in the dark, one that is red, less poisonous, and less flammable, and another that is black, insoluble in most solvents, and the least flammable. The element is used in forming smoke screens, its compounds are used in matches and phosphate fertilizers, and it is a necessary constituent of plant and animal life in bones, nerves, and embryos. Symbol: P; atomic weight: 30.974; atomic number: 15; specific gravity: (yellow) 1.82 at 20°C, (red) 2.20 at 20°C, (black) 2.25–2.69 at 20°C.
any phosphorescent substance.


Nearby words

  1. phosphoro-,
  2. phosphorolysis,
  3. phosphoroscope,
  4. phosphorous,
  5. phosphorous acid,
  6. phosphorus 32,
  7. phosphorus pentoxide,
  8. phosphorus sesquisulfide,
  9. phosphorus trichloride,
  10. phosphorus-32

Origin of phosphorus

1620–30; < New Latin phōsphorus phosphorus; Latin: morning star; see Phosphor


[fos-fer-uh s]

noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for phosphorus

British Dictionary definitions for phosphorus



an allotropic nonmetallic element occurring in phosphates and living matter. Ordinary phosphorus is a toxic flammable phosphorescent white solid; the red form is less reactive and nontoxic: used in matches, pesticides, and alloys. The radioisotope phosphorus-32 (radiophosphorus), with a half-life of 14.3 days, is used in radiotherapy and as a tracer. Symbol: P; atomic no: 15; atomic wt: 30.973 762; valency: 3 or 5; relative density: 1.82 (white), 2.20 (red); melting pt: 44.1°C (white); boiling pt: 280°C (white)
a less common name for a phosphor

Word Origin for phosphorus

C17: via Latin from Greek phōsphoros light-bringing, from phōs light + pherein to bring



a morning star, esp Venus
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for phosphorus



"substance or organism that shines of itself," 1640s, from Latin phosphorus "light-bringing," also "the morning star" (a sense attested in English from 1620), from Greek Phosphoros "morning star," literally "torchbearer," from phos "light," contraction of phaos "light, daylight" (related to phainein "to show, to bring to light;" see phantasm) + phoros "bearer," from pherein "to carry" (see infer).

As the name of a non-metallic chemical element, it is recorded from 1680, originally one among several substances so called; the word used exclusively of the element from c.1750. It was discovered in 1669 by Henning Brand, merchant and alchemist of Hamburg, who derived it from urine. Lavoisier demonstrated it was an element in 1777. According to Flood, "It is the first element whose discoverer is known."

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for phosphorus



n. Symbol P

A highly reactive poisonous nonmetallic element occurring naturally in phosphates, such as hydroxyapatite, and an essential constituent of protoplasm, nerve tissue, and bone. Its radioisotope is used to localize and treat cancers and peritoneal or pleural effusions caused by metastatic disease, to determine blood volume, to study peripheral vascular disease, and to treat blood diseases such as polycythemia vera, chronic myelocytic leukemia, and chronic lymphocytic leukemia. Atomic number 15.
A phosphorescent substance.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for phosphorus




A highly reactive, poisonous nonmetallic element occurring naturally in phosphates, especially in the mineral apatite. It exists in white (or sometimes yellow), red, and black forms, and is an essential component of protoplasm. Phosphorus is used to make matches, fireworks, and fertilizers and to protect metal surfaces from corrosion. Atomic number 15; atomic weight 30.9738; melting point (white) 44.1°C; boiling point 280°C; specific gravity (white) 1.82; valence 3, 5. See Periodic Table.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.