pi

1 of 5

noun (1)

ˈpī 

plural pis ˈpīz 

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)

ˈpī 

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

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Word History

Etymology

Noun (1)

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

Phrases Containing pi

• pi-meson

• pi-meson

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