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

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

Customers and enthusiasts can indulge in pi pie, whether in the form of a mathematical equation, pizza slice or dessert. —Alex Perry, Cincinnati Enquirer, 12 Mar. 2025

Well, so far there are demonstrations of how female engineers and astronauts use pi in their space-exploration work. —Randy McMullen, The Mercury News, 13 Mar. 2025

For round pots, multiply 3.14 (pi) times the radius of the pot’s diameter times the height of the pot. —Tim Johnson, Chicago Tribune, 31 May 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