pi
/paɪ/noun, verb, adjective
pi is spelled P-I: 2 letters and one syllable. It appears 8.3 times per million words in written English, the 8,036th most frequent word form (wordfreq, 2021 data). People search “pi vs pie” about 320 times a month (Google, United States). As a noun, pi means “The sixteenth letter of the Classical and Modern Greek alphabets and the seventeenth in Old Greek” (English Wiktionary, September 2026). The plural of pi is pis.
How many letters and syllables are in pi?
| Letters | 2: P-I |
|---|---|
| Syllables | 1 (from its American pronunciation) |
| In writing | 8.3 times per million words; the 8,036th most frequent word form |
| Wrong spellings searched | none measured in search |
| Pairs people search | |
| Sounds like |
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); Bing searches in the United States: the average month from September 2025 to August 2026 (Microsoft Advertising keyword data through DataForSEO, read September 30, 2026).
How common is pi?
Pi appears 8.3 times per million words in written English, the 8,036th 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 pi?
- /paɪ/
Pi 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-pi.ogg, Wikimedia Commons (author and licence on each file's page).
Words people confuse with pi
Word pairs people search, with the monthly searches for “a vs b” (G: Google, B: Bing, United States).
Sounds like: pie (Wiktionary's homophone list; some hold only in some accents).
Also written: pie.
Sources: Google and Bing searches (September 2025 to August 2026, through DataForSEO); English Wiktionary (homophones, alternative spellings).
Forms of pi
- pis plural
- pies present, singular, he/she/it
- piing participle, present
- pied participle, past
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
What does pi mean?
The meanings the English Wiktionary records, quoted as written there (source below).
noun
- 1
The sixteenth letter of the Classical and Modern Greek alphabets and the seventeenth in Old Greek.
- 2
An irrational and transcendental constant representing the ratio of the circumference of a Euclidean circle to its diameter; approximately 3.14159265.
- 3
Metal type that has been spilled, mixed together, or disordered.
- 4
pica (conventionally, 12 points = 1 pica, 6 picas = 1 inch).
- 5
Piaster.
verb
- 1
To spill or mix printing type.
adjective
- 1
Not part of the usual font character set; especially, non-Roman type or symbols as opposed to standard alphanumeric Roman type.
In computing, pi characters may be entered with special key combinations.
- 2
Pious.
adjective
- 1
Initialism of politically incorrect (see PC).
noun
- 1
Initialism of processing instruction.
- 2
Initialism of partial induction (see AI).
- 3
Initialism of personal injury.
- 4
Initialism of principal investigator (“lead researcher on a grant-funded project”).
- 5
Initialism of private investigator.
- 6
Initialism of parallel import.
- 7
Abbreviation of phosphatidylinositol, a phospholipid component of eukaryotic cell membranes, also abbreviated in PtdIns.
- 8
Initialism of protease inhibitor.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
Pi in Spanish, French, German and Portuguese
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 pi come from?
From Koine Greek πῖ (pî), from Ancient Greek πεῖ (peî), ultimately from Proto-Semitic *pay- (“mouth”). Doublet of pe. Its mathematical use apparently stems from its use as the first letter in περιφέρεια (periphéreia, “periphery; circumference”) and was first cited in 1706 in the Synopsis Palmariorum Matheseos by William Jones.
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).