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

Prompted by a question his son had about the number pi, Brooks began debating math with ChatGPT – particularly the idea that numbers do not just stay the same and can change over time. —Hadas Gold, CNN Money, 5 Sep. 2025

Secondly, the only use case for a computing device with slow eMMC storage should be something like a raspberry pi. —Michael Lydick, PC Magazine, 9 Aug. 2025

What is pi? March 14 (think 3.14) is commonly referred to as Pi Day, a day that aims to celebrate the ratio of the circumference of a circle. —Alexis Simmerman, Austin American Statesman, 2 July 2025

Phenomena in the real world are described by real numbers like 1, –4/3 and pi. —Kenneth Chang, New York Times, 26 Mar. 2025

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

Rhymes for pi

• ai
• aye
• bae
• bi
• buy
• by
• bye
• chai
• chi
• cry
• die
• dry

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