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

This ratio describes the percentages of nitrogen (N), phosphorus (P), and potassium (K) in the fertilizer. —Kim Toscano, Southern Living, 14 Feb. 2025

Other nutrients include vitamin B6, folate, manganese, phosphorus, and more.29 Don’t have time to make your own roasted chickpeas? —Jamie Johnson, Verywell Health, 6 Feb. 2025

Skyr is a good source of calcium and protein, as well as phosphorus, potassium, and magnesium.71 A small study found that adding Icelandic yogurt (skyr) to a resistance training program improved muscle mass, strength, and skeletal muscle support in men aged 64-72. —Lauren O'Connor, Ms, Health, 3 Feb. 2025

Moreover, containing nutrients like nitrogen, phosphorus, potassium, and trace elements, Reclyzer ensures a steady release of fertility and promotes beneficial microbial activity. —Chris Gallagher, USA TODAY, 31 Jan. 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

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