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• phosphorus
  phosphorus

  noun

  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. P; 30.974; 15; (yellow) 1.82 at 20°C, (red) 2.20 at 20°C, (black) 2.25–2.69 at 20°C.
• Phosphorus
  Phosphorus

  noun

  Phosphor.

phosphorus

¹ American  

[fos-fer-uhs] / ˈfɒs fər əs /

noun

phosphori plural

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. P; 30.974; 15; (yellow) 1.82 at 20°C, (red) 2.20 at 20°C, (black) 2.25–2.69 at 20°C.

2. any phosphorescent substance.

3. phosphor.

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Phosphorus ² American  

[fos-fer-uhs] / ˈfɒs fər əs /

noun

1. Phosphor.

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Phosphorus ¹ British  

/ ˈfɒsfərəs /

noun

1. a morning star, esp Venus

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phosphorus ² British  

/ 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. a less common name for a phosphor

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phosphorus Scientific  

/ fŏs′fər-əs /

1. 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.

2. See Periodic Table

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Other Word Forms

Noun Inflected Forms

• phosphori
  plural

Etymology

Origin of phosphorus

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

Example Sentences

See Examples For:

phosphorus Phosphorus phosphori

At the center of the study is phosphorus, especially phosphate, a nutrient that marine organisms need to grow.

From Science Daily ● Jul. 16, 2026

The answer, for that sample, was: mostly Desmodesmus, a green algae that gobbles up phosphorus and nitrogen.

From Slate ● Jun. 27, 2026

Algae need nitrogen and phosphorus to grow, and the Reflecting Pool is primarily fed by the Potomac River, which gets heavy doses of those nutrients from nearby urban and agricultural lands.

From Los Angeles Times ● Jun. 20, 2026

The results deliver readings for specific nutrients such as nitrogen, phosphorus and potassium so that each field can get the right fertilizer, with the right amount of nutrients it needs for more efficient production.

From MarketWatch ● Jun. 2, 2026

Perhaps it is due to the chemistry of phosphorus or sulfur.

From "Cosmos" by Carl Sagan

Phosphorus helps transport energy within plant cells and is critical for early root growth and the formation of seeds and fruit.

From Salon ● Apr. 8, 2026

Phosphorus is naturally occurring but can also come from agricultural runoff, leaky septic systems, stormwater drainage and other human activities.

From Los Angeles Times ● May 8, 2024

Skeletal remains, they argue, were a hot commodity at the beginning of the 19th century: Phosphorus was needed to produce fertilizer, whereas bone char was—bizarrely—a critical part of the process for refining sugar beets.

From Science Magazine ● Apr. 4, 2024

Phosphorus oxychloride is used as a base material by the chemical manufacturing industry, and can be corrosive and highly toxic if it makes contact with the skin.

From BBC ● Mar. 4, 2024

“It really is a bit too thick,” the Head Mistress of Eton was saying to the Director of Crematoria and Phosphorus Reclamation.

From "Brave New World" by Aldous Huxley

It was illuminated by balls of phosphori in glass globes, and its cool, broad halls and stairways were, in the soft light, very beautiful.

From The Certainty of a Future Life in Mars by Gratacap, L. P.

A chandelier of this blue metal was pendant from the ceiling, and in its cup-like extremities, arranged in vertical tiers, were round balls of the phosphori, glowing softly.

From The Certainty of a Future Life in Mars by Gratacap, L. P.

It is indeed a phosphori as, if I recall it aright, the sulphides of barium, strontium, and calcium were upon our earth.

From The Certainty of a Future Life in Mars by Gratacap, L. P.

Around the room were alcoves lit by lamps of the phosphori, and in each alcove a globe of a blue metal upon which were painted sketches like charts or maps.

From The Certainty of a Future Life in Mars by Gratacap, L. P.

At first a glow covered the sides of the houses, the colonnade and dome, while the glass prisms above them sent out rays from their imprisoned balls of phosphori.

From The Certainty of a Future Life in Mars by Gratacap, L. P.