# pi

1
[ pahy ]

noun,plural pis.
1. the 16th letter of the Greek alphabet (Π, π).

2. the consonant sound represented by this letter.

1. 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+.

## Origin of pi

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

## Other definitions for pi (2 of 5)

pi2

### or pie

[ pahy ]

noun,plural pies.
1. printing types mixed together indiscriminately.

2. any confused mixture; jumble.

verb (used with object),pied, pi·ing.
1. to reduce (printing types) to a state of confusion.

2. to jumble.

## Origin of pi

2
First recorded in 1650–60; origin uncertain

## Other definitions for PI (3 of 5)

PI

1. Law. personal injury.

2. principal investigator.

1. Also P.I., p.i. private investigator.

Pi.

abbreviation
1. piaster.

## Other definitions for P.I. (5 of 5)

P.I.

abbreviation
1. Philippine Islands.

2. Also PI, p.i. private investigator.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

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

pi1

/ (paɪ) /

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

2. 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

## Origin of pi

1
C18 (mathematical use): representing the first letter of Greek periphereia periphery

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

pi2

### pie

/ (paɪ) /

nounplural pies
1. a jumbled pile of printer's type

2. a jumbled mixture

verbpies, piing, pied, pies, pieing or pied (tr)
1. to spill and mix (set type) indiscriminately

2. to mix up

## Origin of pi

2
C17: of uncertain origin

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

pi3

/ (paɪ) /

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

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

PI

abbreviation for
1. Philippine Islands

2. 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

[ ]

1. 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.