phosphorus

UK: /ˈfɒsfərəs/ US: /ˈfɑsfərəs/ ,(fos′fər əs)

Inflections of 'phosphorus' (n): npl: phosphori

WordReference Random House Learner's Dictionary of American English © 2025

phos•pho•rus /ˈfɑsfərəs/   n. [uncountable]

1. Chemistry a nonmetallic element and a basic part of plant and animal tissue.

WordReference Random House Unabridged Dictionary of American English © 2025

phos•pho•rus  (fos′fər əs), n., pl. -pho•ri 

(-fə rī′). 
1. 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;
   at. wt.: 30.974;
   at. no.: 15;
   sp. gr.: (yellow) 1.82 at 20°C, (red) 2.20 at 20°C, (black) 2.25–2.69 at 20°C.
2. Chemistry any phosphorescent substance.
3. Chemistry phosphor.

• Neo-Latin phōsphorus phosphorus; Latin: morning star; see Phosphor
• 1620–30

Phos•pho•rus  (fos′fər əs), n. 

1. Phosphor.

Collins Concise English Dictionary © HarperCollins Publishers::

phosphorus / ˈfɒsfərəs/ noun

1. 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)
2. ( phosphori / -rai/)
   a less common name for a phosphor

Etymology: 17th Century: via Latin from Greek phōsphoros light-bringing, from phōs light +pherein to bring

WordReference Random House Unabridged Dictionary of American English © 2025

phos•phor  (fos′fər, -fôr), n. 

1. Physics, Chemistry any of a number of substances that exhibit luminescence when struck by light of certain wavelengths, as by ultraviolet.
2. [Literary.] a phosphorescent substance.

adj. 

3. [Archaic.] phosphorescent.

• Latin Phōsphorus Phosphor
• French phosphore
• 1625–35

Phos•phor  (fos′fər, -fôr), n. 

1. Astronomy the morning star, esp. Venus.

Also, Phos•phore  (fos′fôr, -fōr), Phosphorus. 

• Greek Phōsphóros the morning star, literally, the light-bringing one, equivalent. to phôs light + -phoros bringing; see -phorous
• Latin Phōsphorus
• 1625–35

phosphor-, 

1. Chemistry var. of phosphoro- before a vowel:
   phosphorate.

Collins Concise English Dictionary © HarperCollins Publishers::

Phosphorus / ˈfɒsfərəs/ noun

1. a morning star, esp Venus