# pi

^{1}

[ pahy ]

/ paɪ /

Save This Word!

noun, plural pis.

the 16th letter of the Greek alphabet (Π, π).

the consonant sound represented by this letter.

Mathematics.

- the letter π, used as the symbol for the ratio of the circumference of a circle to its diameter.
- the ratio itself: 3.141592+.

QUIZ

GOOSES. GEESES. I WANT THIS QUIZ ON PLURAL NOUNS!

Test how much you really know about regular and irregular plural nouns with this quiz.

Question 1 of 9

Which of the following nouns has an irregular plural form?

## Origin of pi

^{1}

1835–45; <Greek pî, peî; used in mathematics to represent Greek periphérion periphery

## Other definitions for pi (2 of 5)

pi

^{2}### or pie

[ pahy ]

/ paɪ /

noun, plural pies.

printing types mixed together indiscriminately.

any confused mixture; jumble.

verb (used with object), pied, pi·ing.

to reduce (printing types) to a state of confusion.

to jumble.

## Origin of pi

^{2}

First recorded in 1650–60; origin uncertain

## Other definitions for pi (3 of 5)

## Other definitions for pi (4 of 5)

Pi.

### or pi.

abbreviation

piaster.

## Other definitions for pi (5 of 5)

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

## How to use pi in a sentence

## British Dictionary definitions for pi (1 of 4)

pi

^{1}/ (paɪ) /

noun plural pis

the 16th letter in the Greek alphabet (Π, π), a consonant, transliterated as p

maths a transcendental number, fundamental to mathematics, that is the ratio of the circumference of a circle to its diameter. Approximate value: 3.141 592…; symbol: π

## Word Origin for pi

C18 (mathematical use): representing the first letter of Greek periphereia periphery

## British Dictionary definitions for pi (2 of 4)

pi

^{2}### pie

/ (paɪ) /

noun plural pies

a jumbled pile of printer's type

a jumbled mixture

verb pies, piing, pied, pies, pieing or pied (tr)

to spill and mix (set type) indiscriminately

to mix up

## Word Origin for pi

C17: of uncertain origin

## British Dictionary definitions for pi (3 of 4)

## British Dictionary definitions for pi (4 of 4)

PI

abbreviation for

Philippine Islands

private investigator

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

## Medical definitions for pi (1 of 3)

π

The Greek letter pi. Entries beginning with this character are alphabetized under pi.

## Medical definitions for pi (2 of 3)

pi

[ pī ]

n. pl. pis

The 16th letter of the Greek alphabet.

## Medical definitions for pi (3 of 3)

pI

[ pē′ī′ ]

n.

The pH value for the isoelectric point of a given substance in solution.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

## Scientific definitions for pi

pi

[ pī ]

An irrational number that has a numerical value of 3.14159265358979… and is represented by the symbol π. It expresses the ratio of the circumference to the diameter of a circle and appears in many mathematical expressions.

The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

## Cultural definitions for pi

pi

[ (peye) ]

The irrational number obtained by dividing the length of the diameter of a circle into its circumference. Pi is approximately 3.1416. The sign for pi is π.

The New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.