pi

1 of 5

noun (1)

plural pis ˈpīz How to pronounce pi (audio)
1
: the 16th letter of the Greek alphabet see Alphabet Table
2
a
: the symbol π denoting the ratio of the circumference of a circle to its diameter
b
: the ratio itself : a transcendental number having a value rounded to eight decimal places of 3.14159265

pi

2 of 5

noun (2)

variants or less commonly pie
plural pies
1
: type that is spilled or mixed
2
: a pi character or matrix

pi

3 of 5

verb

variants or less commonly pie
pied; piing or pieing

transitive verb

: to spill or throw (type or type matter) into disorder

intransitive verb

: to become pied

pi

4 of 5

adjective

variants or less commonly pie
1
: not intended to appear in final printing
pi lines
2
: capable of being inserted only by hand
pi characters

PI

5 of 5

abbreviation

1
Philippine Islands
2
private investigator
3
programmed instruction

Examples of pi in a Sentence

Recent Examples on the Web
Noun
The nickname is based on the Greek letter that represents the number value of pi twice, which is about 6.28, which is the date of Musk’s birthday on June 28. David Chiu, Peoplemag, 12 Sep. 2023 Pumpkin pi Who helped the mini pumpkin cross the road? Briannah Rivera, Seventeen, 6 July 2023 Pi Day is a celebration of pi, the mathematical constant that starts 3.14, which also can be read as March 14. Deborah Martin, San Antonio Express-News, 14 Mar. 2023 Each year, the concept of pi seems to grow annually in crossover popularity, via memes, novelty T-shirts, and all the attendant hoopla around Pi Day. WIRED, 14 Mar. 2023 This tells us, in particular, that the uncertainty in the position of a quantum particle multiplied by the uncertainty in its momentum — sort of the measure of like how fast this is moving — that quantity, that product has to be larger than what is known as Planck’s constant over 2 pi, okay? Steven Strogatz, Quanta Magazine, 26 July 2023 In 1988, Larry Shaw, a former staff physicist at the Exploratorium museum in San Francisco, linked March 14 (3/14) with the digits of pi (3.14) and celebrated the first Pi Day with fruit pies and tea. Arizona Republic, The Arizona Republic, 14 Mar. 2023 Pi Day is in honor of pi, the symbol used in mathematics to represent a constant — the ratio of the circumference of a circle to its diameter — which is 3.14159. Ricardo Delgado, San Antonio Express-News, 14 Mar. 2023 Pi Day got its start in 1988 in San Francisco, when Larry Shaw, the legendary technical curator of the city’s Exploratorium, saw the connection between March 14 (3.14) and pi (3.14159…). David Grossman, Popular Mechanics, 14 Mar. 2022 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'pi.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

Noun (1)

Middle Greek, from Greek pei, of Semitic origin; akin to Hebrew pe

Noun (2)

origin unknown

First Known Use

Noun (1)

15th century, in the meaning defined at sense 1

Noun (2)

circa 1659, in the meaning defined at sense 1

Verb

1889, in the meaning defined at transitive sense

Adjective

circa 1940, in the meaning defined at sense 1

Time Traveler
The first known use of pi was in the 15th century

Dictionary Entries Near pi

Cite this Entry

“Pi.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/pi. Accessed 9 Dec. 2023.

Kids Definition

pi

noun
ˈpī
plural pis
ˈpīz
1
: the 16th letter of the Greek alphabet
Π or π
2
a
: the symbol π representing the ratio of the circumference of a circle to its diameter
b
: the ratio itself having a value of approximately 3.1416

Legal Definition

P&I

1 of 2 abbreviation
principal and interest

PI

2 of 2 abbreviation
private investigator

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