phosphorus

noun

phos·​pho·​rus ˈfäs-f(ə-)rəs How to pronounce phosphorus (audio)
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 How to pronounce phosphorus (audio)
: 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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
In terms of formulation, our experts recommend a balanced fertilizer with a nitrogen-phosphorus-potassium (NPK) ratio of 10-10-10 or 20-20-20. — Madeline Buiano, Martha Stewart, 9 July 2026 As part of the Middle Snake Watershed Advisory Group, the Idaho Conservation League is advising the state Department of Environmental Quality to revise limits on phosphorus pollution in the middle portion of the Snake River. — Hannah Smith updated July 8, Idaho Statesman, 8 July 2026 Second, adding synthetic fertilizers rich in phosphorus or nitrogen can disrupt the harmonious partnership between plants and microbes. — Esther Ndumi Ngumbi, The Conversation, 8 July 2026 But according to studies, that water contains starches, nutrients, and minerals leached from rice, including nitrogen, phosphorus, potassium, zinc, and B vitamins, all of which are good for plants. — Leanne Potts, Better Homes & Gardens, 7 July 2026 See All Example Sentences for phosphorus

Word History

Etymology

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

First Known Use

1680, in the meaning defined at sense 1

Time Traveler
The first known use of phosphorus was in 1680

Rhymes for phosphorus

See All Rhymes for phosphorus

Browse Nearby Words

phosphorroesslerite
phosphorus
phosphorus chloride
See all Nearby Words

Cite this Entry

“Phosphorus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/phosphorus. Accessed 15 Jul. 2026.

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Kids Definition

phosphorus

noun
phos·​pho·​rus ˈfäs-f(ə-)rəs How to pronounce phosphorus (audio)
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 How to pronounce phosphorus (audio)
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

More from Merriam-Webster on phosphorus

Nglish: Translation of phosphorus for Spanish Speakers

Britannica.com: Encyclopedia article about phosphorus

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