Jump To:

• 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.

---

Phosphorus ² American  

[fos-fer-uhs] / ˈfɒs fər əs /

noun

1. Phosphor.

---

Phosphorus ¹ British  

/ ˈfɒsfərəs /

noun

1. a morning star, esp Venus

---

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

---

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

---

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

During the same period, average levels of calcium and phosphorus decreased.

From Science Daily ● Aug. 15, 2026

The conclusion was that far more phosphorus was coming into the catchment than was being removed through food production.

From BBC ● Jul. 22, 2026

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

From Slate ● Jun. 27, 2026

Longer-term fixes would have to address what makes the Reflecting Pool so ideal for algae, such as its depth, darker color and inflow of nitrogen and phosphorus.

From Los Angeles Times ● Jun. 20, 2026

This suggested that phosphorus would be a better carrier of therapeutic radiation than radio-sodium, since the latter distributes itself all through the body as salt, attenuating its effect.

From "Big Science" by Michael Hiltzik

Phosphorus - found in fertiliser and processed livestock feed - is considered to be one of the substances of most concern.

From BBC ● Jul. 22, 2026

Phosphorus is also capable of forming stable 2D structures.

From Science Daily ● Feb. 16, 2026

Phosphorus is also an essential building block of life.

From Salon ● May 29, 2024

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

“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

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 L. P. Gratacap

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 L. P. Gratacap

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 L. P. Gratacap

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 L. P. Gratacap

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 L. P. Gratacap