psi
/psaɪ/noun, symbol
psi is spelled P-S-I: 3 letters and one syllable. It appears 2.8 times per million words in written English, the 16,005th most frequent word form (wordfreq, 2021 data). As a noun, psi means “The twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek” (English Wiktionary, September 2026). The plural of psi is psis.
How many letters and syllables are in psi?
| Letters | 3: P-S-I |
|---|---|
| Syllables | 1 (from its American pronunciation) |
| In writing | 2.8 times per million words; the 16,005th most frequent word form |
| Wrong spellings searched | none measured in search |
| Same letters |
Sources: letters and syllables from the English Wiktionary's hyphenation or pronunciation and the CMU Pronouncing Dictionary; written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media); rhymes and same-letter words are computed by PlainSpell from its own word list.
How common is psi?
Psi appears 2.8 times per million words in written English, the 16,005th most frequent word form in the list.
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How do you pronounce psi?
- /psaɪ/
- /saɪ/
Psi has one syllable (counted from its American pronunciation in the CMU Pronouncing Dictionary).
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Recordings: En-us-psi.ogg, En-us-psi-mental.ogg, Wikimedia Commons (author and licence on each file's page).
What rhymes with psi?
No other word on PlainSpell ends in the same sounds as psi.
Spelled with the same letters in another order: sip, isp.
Computed by PlainSpell from the pronunciations in the English Wiktionary (dump of September 2, 2026): a rhyme shares every sound from the last stressed vowel to the end; ordered by written frequency (wordfreq 3.1).
Forms of psi
- psis plural
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
What does psi mean?
The meanings the English Wiktionary records, quoted as written there (source below).
noun
- 1
The twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek.
- 2
A form of psychic energy.
When an event is classified as a psi phenomenon, it is claimed that all known channels for the apparent interaction have been eliminated.
symbol
- 1
Pound per square inch (an imperial unit of pressure)
noun
- 1
Initialism of pre-sentence investigation.
- 2
Initialism of protein structure initiative.
- 3
Initialism of pollutant safety/standard index (measurement of the air pollutant such as haze).
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
Psi in Spanish, French, German and Portuguese
In the sense Greek letter:
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Translations are Wiktionary's, by sense; a linked word has its own PlainSpell page.
Where does psi come from?
From Middle English psi, from Latin psī, from Ancient Greek ψεῖ (pseî), the name for the twenty-third letter of the alphabet (Ψ, ψ).
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).