# pi

^{1}

[ pahy ]

/ paɪ /

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### 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+.

## QUIZZES

#### QUIZ YOURSELF ON PARENTHESES AND BRACKETS APLENTY!

Set some time apart to test your bracket symbol knowledge, and see if you can keep your parentheses, squares, curlies, and angles all straight!

Question 1 of 7

Let’s start with some etymology: What are the origins of the typographical word “bracket”?

First appeared around 1750, and is related to the French word “braguette” for the name of codpiece armor.

First appeared in 1610, based on the French word “baguette” for the long loaf of bread.

First appeared in 1555, and is related to the French word “raquette” for a netted bat.

TAKE THE QUIZ TO FIND OUT ## Origin of pi

^{1}

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

## Words nearby pi

## Definition 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

## Definition for pi (3 of 5)

## Definition for pi (4 of 5)

Pi.

### or pi.

### abbreviation

piaster.

## Definition for pi (5 of 5)

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021

## Example sentences from the Web for pi

## 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)

pi

[ pī ]

### n. pl. pis

The 16th letter of the Greek alphabet.

## Medical definitions for pi (2 of 3)

π

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

## 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.