# 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.
1. the letter π, used as the symbol for the ratio of the circumference of a circle to its diameter.
2. the ratio itself: 3.141592+.
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## Origin ofpi

1
1835–45; <Greek pî, peî; used in mathematics to represent Greek periphérion periphery

## Other definitions for pi (2 of 5)

pi2

### 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 ofpi

2
First recorded in 1650–60; origin uncertain

## Other definitions for pi (3 of 5)

PI

Law. personal injury.
principal investigator.
Also P.I., p.i.

Pi.

abbreviation
piaster.

## Other definitions for pi (5 of 5)

P.I.

abbreviation
Philippine Islands.
Also PI, p.i.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

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

pi1
/ (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)

pi2

### 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)

pi3
/ (paɪ) /

British slang short for pious (def. 2), pious (def. 3)

## 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

## 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.