Phosphorous or phosphorus?
phosphorous is an adjective meaning “Of or pertaining to phosphorus”; phosphorus is a noun meaning “A chemical element (symbol P) with an atomic number of 15, that exists in…”. Use phosphorous as an adjective and phosphorus as a noun. In written English (wordfreq, 2021 data) phosphorus is about 5.5 times as common as phosphorous.
What is the difference between phosphorous and phosphorus?
| phosphorous | phosphorus | |
|---|---|---|
| Part of speech | adjective | noun |
| Meaning | Of or pertaining to phosphorus Resembling phosphorus | A chemical element (symbol P) with an atomic number of 15, that exists in several allotropic forms An atom of this element |
| Example | none recorded | For quotations using this term, see Citations:phosphorus |
| Forms | none | phosphoruses, phosphori |
| Pronunciation | not recorded | /ˈfɒs.fə.ɹəs/ /ˈfɒs.fɹəs/ /ˈfɑs.fɚ.əs/ |
| In writing | about once in every 3 million words | 1.8 times per million words |
Sources: phosphorous and phosphorus in the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
Every current meaning of phosphorous and phosphorus
phosphorous
- 1
Of or pertaining to phosphorus
- 2
Resembling phosphorus
- 3
Of, relating to, or containing trivalent phosphorus
phosphorus
- 1
A chemical element (symbol P) with an atomic number of 15, that exists in several allotropic forms
For quotations using this term, see Citations:phosphorus
- 2
An atom of this element
Source: the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); obsolete, archaic, dialect and rare senses left out.
Which is more common, phosphorous or phosphorus?
phosphorous appears about once in every 3 million words; phosphorus 1.8 times per million words.
phosphorous about once in every 3 million wordsphosphorus 1.8 times per million words
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How many people search phosphorous vs phosphorus?
“phosphorous vs phosphorus” is searched about 260 times a month on Google and 10 on Bing in the United States. Google counts close variants of a query together (“phosphorus vs phosphorous”, “phosphorous or phosphorus”).
Sources: Google Ads keyword data through DataForSEO and Microsoft Advertising keyword data through DataForSEO, the average month from September 2025 to August 2026.