pi
^{1}[ pahy ]
/ paɪ /

noun, plural pis.
the 16th letter of the Greek alphabet (II, 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+.
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Nearby words
Origin of pi
^{1}1835–45; < Greek pî, peî; used in mathematics to represent Greek periphérion periphery
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)
Definition for pi (5 of 5)
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples 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
Word Origin and History for pi
pi
Greek letter, from Hebrew, literally "little mouth." As the name of the mathematical constant, from 1841 in English, used in Latin 1748 by Swiss mathematician Leonhart Euler (17071783), as an abbreviation of Greek periphereia "periphery." For the meaning "printer's term for mixed type," see pie (3).
Online Etymology Dictionary, © 2010 Douglas Harper
Medicine definitions for pi (1 of 2)
pi
[ pī ]
n. pl. pis
The 16th letter of the Greek alphabet.
Medicine definitions for pi (2 of 2)
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.
Science 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.
Culture 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.