# pi1

[pahy] /paɪ/
noun, plural pis.
1.
the 16th letter of the Greek alphabet (II, π).
2.
the consonant sound represented by this letter.
3.
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+.
Origin of pi1
1835-1845
1835-45; < Greek pî, peî; used in mathematics to represent Greek periphérion periphery
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for π
Historical Examples
• As it is, our trigonometry being founded on the circle, π first appears as the ratio stated.

Augustus De Morgan
• It was he who first carried the computation of π to 35 decimal places.

Augustus De Morgan
• Hence g may be written for l, but only once: do it twice, and you require the time to be π √(l2 : g2).

Augustus de Morgan
• In one of the notes Legendre gives a proof of the irrationality of π.

• Further studies of the interactions of π mesons are made in the meson cave.

• This leads to defining the ratio of the circumference to the diameter as π.

David Eugene Smith
• If p be the length of the perpendicular, either of these angles is denoted by Π(p).

• Probably the earliest approximation of the value of π was 3.

David Eugene Smith
• And so I have come in contact with him on 666 as well as on π!

Augustus de Morgan
• The factors 1/π and -1/π are taken account of in the graduation of the wheels.

British Dictionary definitions for π

## pi1

/paɪ/
noun (pl) 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
Word Origin
C18 (mathematical use): representing the first letter of Greek periphereiaperiphery

## pi2

/paɪ/
noun (pl) pies
1.
a jumbled pile of printer's type
2.
a jumbled mixture
verb (transitive) pies, piing, pied, pies, pieing, pied
3.
to spill and mix (set type) indiscriminately
4.
to mix up
Word Origin
C17: of uncertain origin

## pi3

/paɪ/
1.
(Brit, slang) short for pious (sense 2), pious (sense 3)

## PI

abbreviation
1.
Philippine Islands
2.
private investigator
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for π

## pi

n.

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 (1707-1783), 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
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π in Medicine

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

pi (pī)
n. pl. pis

Symbol π The 16th letter of the Greek alphabet.

pI (pē'ī')
n.
The pH value for the isoelectric point of a given substance in solution.

The American Heritage® Stedman's Medical Dictionary
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π in Science
 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
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π in Culture
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 American Heritage® New Dictionary of Cultural Literacy, Third Edition
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Slang definitions & phrases for π

### PI

noun

1. A pimp (1931+)
2. A private detective; op (1960+)
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D.
Copyright (C) 2007 by HarperCollins Publishers.
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Related Abbreviations for π

Pali

### Pi

inorganic phosphate

### PI

1.
performance indicator
2.
politically incorrect
3.
present illness
4.
primary infertility
5.
principal investigator
6.
private investigator
The American Heritage® Abbreviations Dictionary, Third Edition
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### Difficulty index for pi

Many English speakers likely know this word

### Word Value for π

0
0
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