phosphorus

¹ American  

[fos-fer-uhs] / ˈfɒs fər əs /

noun

plural

phosphori

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

---

Etymology

Origin of phosphorus

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

Example Sentences

"Urine does naturally contain all of the nutrients that plants need such as nitrogen, phosphorus and potassium, but it also contains a variety of contaminants," explained Olivia Wilson, NPK Recovery's research and development scientist.

From BBC • Apr. 2, 2026

This includes phosphorus and nitrogen from the Middle East, she added.

From Barron's • Mar. 10, 2026

“If you’re limiting their ability to produce glyphosates, you’re limiting their ability to produce phosphorus and profit from it.”

From Salon • Mar. 2, 2026

Under carefully controlled conditions, phosphorus atoms can organize themselves into short, straight lines on a silver substrate.

From Science Daily • Feb. 16, 2026

John’s medical hypothesis was based on the observation that phosphorus naturally concentrates in bone marrow.

From "Big Science" by Michael Hiltzik