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

Words Nearby pi

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.

Other definitions for Pi. (4 of 5)

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

How to use pi in a sentence

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) /


adjective
  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.

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.