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

Through geolocating and verifying seven images, Human Rights Watch said Israel fired white phosphorus using artillery at residential areas in the southern Lebanese village of Yohmor. —Arkansas Online, 10 Mar. 2026

The Israeli military illegally used white phosphorus munitions over homes in the southern Lebanese town Yohmor on March 3, posing a threat to civilians, Human Rights Watch said in a report on Monday. —Rebecca Shabad, NBC news, 10 Mar. 2026

The white phosphorus then ignites and burns intensely, destroying the agents by incinerating them – a method meant to reduce the risk of spreading the materials and to limit potential harm to civilians and the surrounding environment. —Bojan Stojkovski, Interesting Engineering, 8 Mar. 2026

Labels must disclose the amounts of nitrogen (N), phosphorus (P), and potassium (K). —Rita Perwich, San Diego Union-Tribune, 7 Mar. 2026

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