\ ˈpī How to pronounce pi (audio) \
plural pis\ ˈpīz How to pronounce pi (audio) \

Definition of pi

 (Entry 1 of 5)

1 : the 16th letter of the Greek alphabet — see Alphabet Table
2a : the symbol π denoting the ratio of the circumference of a circle to its diameter
b : the ratio itself : a transcendental number having a value rounded to eight decimal places of 3.14159265
\ ˈpī How to pronounce pi (audio) \
variants: or less commonly
plural pies

Definition of pi (Entry 2 of 5)

1 : type that is spilled or mixed
2 : a pi character or matrix


variants: or less commonly pie
pied; piing or pieing

Definition of pi (Entry 3 of 5)

transitive verb

: to spill or throw (type or type matter) into disorder

intransitive verb

: to become pied
variants: or less commonly pie

Definition of pi (Entry 4 of 5)

1 : not intended to appear in final printing pi lines
2 : capable of being inserted only by hand pi characters

Definition of PI (Entry 5 of 5)

1 Philippine Islands
2 private investigator
3 programmed instruction

First Known Use of pi

Noun (1)

15th century, in the meaning defined at sense 1

Noun (2)

circa 1659, in the meaning defined at sense 1


1889, in the meaning defined at transitive sense


circa 1940, in the meaning defined at sense 1

History and Etymology for pi

Noun (1)

Middle Greek, from Greek pei, of Semitic origin; akin to Hebrew pe

Noun (2)

origin unknown

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The first known use of pi was in the 15th century

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Cite this Entry

“Pi.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/pi. Accessed 27 May. 2022.

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More Definitions for pi


\ ˈpī How to pronounce pi (audio) \
plural pis\ ˈpīz \

Kids Definition of pi

1 : the symbol π representing the ratio of the circumference of a circle to its diameter
2 : the ratio itself having a value of about 3.1416



Legal Definition of P&I

 (Entry 1 of 2)

principal and interest



Legal Definition of PI (Entry 2 of 2)

private investigator

More from Merriam-Webster on pi

Nglish: Translation of pi for Spanish Speakers

Britannica.com: Encyclopedia article about pi


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