Pi Definition & Meaning

American

British

Scientific

Cultural

Etymology

Examples

Related Words

Synonyms pi 1 American [pahy] / paɪ /

noun

plural

pis

1. the 16th letter of the Greek alphabet (Π, 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+.

pi 2 American [pahy] / paɪ / Or pie

noun

plural

pies

1. printing types mixed together indiscriminately.

2. any confused mixture; jumble.

verb (used with object)

pied, piing

1. to reduce (printing types) to a state of confusion.

2. to jumble.

PI 3 American

1. Law. personal injury.

2. principal investigator.

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

Pi. 4 American Or pi.

abbreviation

1. piaster.

P.I. 5 American

abbreviation

1. Philippine Islands.

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

pi 1 British / paɪ /

noun

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

"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 pi 2 British / paɪ /

noun

1. a jumbled pile of printer's type

2. a jumbled mixture

"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

verb

1. to spill and mix (set type) indiscriminately

2. to mix up

"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 PI 3 British

abbreviation

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 pi 4 British / paɪ /

adjective

1. slang short for pious pious

"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 pi Scientific / pī /

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.

pi Cultural

1. 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.

Etymology

Origin of pi1

First recorded in 1835–45; from Greek pî, peî, used in mathematics to represent Greek periphérion periphery ( def. )

Origin of pi2

First recorded in 1650–60; origin uncertain

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

In science-fiction scenarios of first contact with extraterrestrials, humans usually bootstrap a common language with mathematics, demonstrating that we know the digits of pi and so forth.

From The Wall Street Journal

In recent decades, advances in computing have pushed this familiar constant far beyond the classroom, with powerful supercomputers now calculating pi to trillions of decimal places.

From Science Daily

Classical computers have managed the calculation for molecules as large as pentacene, a chain of five hydrocarbon rings with 22 electrons in “pi” covalent bonds, which govern the molecule’s shape and reactivity.

From Science Magazine

That ratio is pi, which means the circumference is always going to be about 3.14 times as long as the diameter.

From NewsForKids.net

It’s the first Greek letter in the words “periphery” and “perimeter,” and pi is the ratio of a circle’s periphery — or circumference — to its diameter.

From Seattle Times

Related Words

• inquiry agent
• private detective
• private dick
• private eye
• private investigator
• sleuth

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.