phosphorus

noun

phos·​pho·​rus ˈfäs-f(ə-)rəs 

often attributive

1

: a phosphorescent substance or body

especially : one that shines or glows in the dark

2

or less commonly phosphorous

ˈfäs-f(ə-)rəs 

: a nonmetallic element of the nitrogen family with atomic number 15 that occurs widely in combination especially as phosphates, that is essential for life in all known organisms, and that is used especially in fertilizers and organophosphorus compounds see Chemical Elements Table

Examples of phosphorus in a Sentence

Recent Examples on the Web

Although water board inspectors originally found high levels of ammonium-nitrate and phosphorus at the egg ranch, later tests found almost no contaminants after the facility began putting all of the egg wash wastewater into temporary holding tanks and hauling it offsite. —Regina Elling, San Diego Union-Tribune, 25 June 2025

Some examples of minerals include calcium, phosphorus, sodium, potassium, and iron.9 Each mineral serves a different function in your body. —Isabel Vasquez Rd Ldn, Health, 24 June 2025

After new growth is visible on kangaroo paws, fertilize with any complete fertilizer (containing N-P-K, an abbreviation for nitrogen, phosphorus and potassium). —Joshua Siskin, Oc Register, 19 June 2025

The California coastline can experience large-scale blooms of algae called Pseudo-nitzschia australis when warm water combines with excess nutrients such as nitrogen and phosphorus. —Clara Harter, Los Angeles Times, 29 May 2025

Word History

Etymology

New Latin, from Greek phōsphoros light-bearing — more at phosphor

First Known Use

1680, in the meaning defined at sense 1

Rhymes for phosphorus

• phosphorous
• organophosphorus

Kids Definition

phosphorus

noun

phos·​pho·​rus ˈfäs-f(ə-)rəs 

1

: a phosphorescent substance

especially : one that glows in the dark

2

: a nonmetallic element that occurs widely especially as phosphates see element

phosphoric

fäs-ˈfȯr-ik

-ˈfär-

adjective

phosphorous

ˈfäs-f(ə-)rəs;

fäs-ˈfōr-əs

-ˈfȯr-

adjective

Medical Definition

phosphorus

noun

phos·​pho·​rus ˈfäs-f(ə-)rəs 

often attributive

: a nonmetallic multivalent element that occurs widely in combined form especially as inorganic phosphates in minerals, soils, natural waters, bones, and teeth and as organic phosphates in all living cells and that exists in several allotropic forms

—symbol P see Chemical Elements Table