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Pi (letter)

Pi (; Greek: , uppercase Π, lowercase π) is the sixteenth letter of the Greek alphabet, representing . In the system of Greek numerals it has a value of 80. It was derived from the Phoenician letter pe . Letters that arose from pi include Cyrillic Pe (П, п), Coptic pi (Ⲡ, ⲡ), and Gothic pairthra (????).

Pi (disambiguation)

Pi or is a mathematical constant equal to a circle's circumference divided by its diameter.

Pi, π or Π may also refer to:

  • Pi (letter), a Greek letter

Pi (magazine)

Pi is the name of the official student publication of the University College London Union. It publishes a free monthly magazine during academic term time in addition to its website.

Pi (instrument)

Pi (, ) is the generic term for any of a variety of quadruple reed oboes used in the traditional music of Thailand. It is very similar in construction and playing technique to the Cambodian sralai.

Pi (surname)

Pi is the Mandarin pinyin romanization of the Chinese surname written in Chinese character. It is romanized P'i in Wade–Giles, and Pei in Cantonese. Pi is listed 85th in the Song dynasty classic text Hundred Family Surnames. It is not among the 300 most common surnames in China.


The number is a mathematical constant, the ratio of a circle's circumference to its diameter, commonly approximated as 3.14159. It has been represented by the Greek letter "" since the mid-18th century, though it is also sometimes spelled out as "pi" .

Being an irrational number, cannot be expressed exactly as a fraction (equivalently, its decimal representation never ends and never settles into a permanent repeating pattern). Still, fractions such as 22/7 and other rational numbers are commonly used to approximate . The digits appear to be randomly distributed. In particular, the digit sequence of is conjectured to satisfy a specific kind of statistical randomness, but to date no proof of this has been discovered. Also, is a transcendental number – a number that is not the root of any non-zero polynomial having rational coefficients. This transcendence of implies that it is impossible to solve the ancient challenge of squaring the circle with a compass and straightedge.

Ancient civilizations needed the value of to be computed accurately for practical reasons. It was calculated to seven digits, using geometrical techniques, in Chinese mathematics and to about five in Indian mathematics in the 5th century AD. The historically first exact formula for , based on infinite series, was not available until a millennium later, when in the 14th century the Madhava–Leibniz series was discovered in Indian mathematics. In the 20th and 21st centuries, mathematicians and computer scientists discovered new approaches that, when combined with increasing computational power, extended the decimal representation of to, as of 2015, over 13.3 trillion (10) digits. Practically all scientific applications require no more than a few hundred digits of , and many substantially fewer, so the primary motivation for these computations is the human desire to break records. However, the extensive calculations involved have been used to test supercomputers and high-precision multiplication algorithms.

Because its definition relates to the circle, is found in many formulae in trigonometry and geometry, especially those concerning circles, ellipses or spheres. Because of its special role as an eigenvalue, appears in areas of mathematics and the sciences having little to do with the geometry of circles, such as number theory and statistics. It is also found in cosmology, thermodynamics, mechanics and electromagnetism. The ubiquity of makes it one of the most widely known mathematical constants both inside and outside the scientific community: Several books devoted to it have been published, the number is celebrated on Pi Day and record-setting calculations of the digits of often result in news headlines. Attempts to memorize the value of with increasing precision have led to records of over 70,000 digits.

Pi (state)

Pi was a Zhou dynasty (1045–256 BC) vassal state in ancient China. Also known as Xue , Pi was ruled by members of the Ren family.

It’s progenitor Xi Zhong , had been the Minister of Chariots for Yu the Great during the Xia Dynasty (~2070–1600 BCE) who was given land at the confluence of the Dan and Yi Rivers in the southern part of modern-day Shandong Province.

During the Western Zhou Dynasty (1046–771 BCE), the State of Pi shares a border with the State of Song to the east and the State of Tan to the north.

Pi (art project)

Pi is the name of a multimedia installation in the vicinity of the Viennese Karlsplatz. Pi is located in the Opernpassage between the entrance to the subway and the subway stop in Secession near the Naschmarkt. The individual behind the project was the Canadian artist Ken Lum from Vancouver.

Pi, under construction from January 2005 to November 2006 and opened in December 2006, consists of statistical information and a representation of π to 478 decimal places. A more recent project is the calculation of the decimal places of π, indicating the importance of the eponymous media for installation of their number and infinity.

The exhibit is 130 meters long. In addition to the number pi, there is a total of 16 factoids of reflective display cases that convey a variety of statistical data in real time. Apart from the World population there are also topics such as the worldwide number of malnourished children and the growth of Sahara since the beginning of the year. Even less serious issues such as the number of eaten Wiener Schnitzels in Vienna of the given year and the current number of lovers in Vienna are represented.

In the middle of the passage standing there is a glass case with images, texts and books on the subjects of population and migration.

The scientific data were developed jointly by Ken Lum and the Institute SORA. "Pi" is to show that contemporary art is in a position to connect art to science, architecture and sociology. The aim of this project was to transform the Karlsplatz into a "vibrant place to meet, with communicative artistic brilliance."

Pi (film)

Pi, also titled , is a 1998 American surrealist psychological thriller film written and directed by Darren Aronofsky in his directorial debut. The film earned Aronofsky the Directing Award at the 1998 Sundance Film Festival, the Independent Spirit Award for Best First Screenplay and the Gotham Open Palm Award. The title refers to the mathematical constant pi. The film is notable for its covering of an array of themes including religion, mysticism and the relationship of the universe to mathematics. The story about a mathematician and the obsession with mathematical regularity contrasts two seemingly irreconcilable entities: the imperfect, irrational humanity and the rigor and regularity of mathematics, specifically number theory.

The Collaborative International Dictionary


Pi \Pi\ (p[=e]` [imac]"), n. The inorganic orthophoshate ion; -- a symbol used in biochemistry. [acronym]


Pi \Pi\, n. [See Pica, Pie magpie, service-book.] (Print.) A mass of type confusedly mixed or unsorted. [Written also pie.]


Pi \Pi\ (p[imac]), n. [Gr. pi^.]

  1. A Greek letter ([Pi], [pi]) corresponding to the Roman letter P.

  2. Specifically: (Math.) The letter [pi], [Pi], as used to denote the number or quotient approximately expressing the ratio of the circumference of a circle to its diameter; also, the quotient or the ratio itself. The value of the quotient pi, to twenty decimal places, is

  3. 14159265358979323846 (see note). The number pi is an irrational number, i.e. it cannot be expressed as the quotient of two integers. It is also a transcendental number, i.e. it cannot be expressed as a root of an algebraic equation with a finite number of terms; and from this fact follows the impossibility of the quadrature of the circle by purely algebraic processes, or by the aid of a ruler and compass.

    Note: The first 1000 decimal digits of the number pi are as displayed below. The digits are arranged as five sets of ten digits per line in twenty lines, proceeding left to right in each line. 3. 1415926535 8979323846 2643383279 5028841971 6939937510 5820974944 5923078164 0628620899 8628034825 3421170679 8214808651 3282306647 0938446095 5058223172 5359408128 4811174502 8410270193 8521105559 6446229489 5493038196 4428810975 6659334461 2847564823 3786783165 2712019091 4564856692 3460348610 4543266482 1339360726 0249141273 7245870066 0631558817 4881520920 9628292540 9171536436 7892590360 0113305305 4882046652 1384146951 9415116094 3305727036 5759591953 0921861173 8193261179 3105118548 0744623799 6274956735 1885752724 8912279381 8301194912 9833673362 4406566430 8602139494 6395224737 1907021798 6094370277 0539217176 2931767523 8467481846 7669405132 0005681271 4526356082 7785771342 7577896091 7363717872 1468440901 2249534301 4654958537 1050792279 6892589235 4201995611 2129021960 8640344181 5981362977 4771309960 5187072113 4999999837 2978049951 0597317328 1609631859 5024459455 3469083026 4252230825 3344685035 2619311881 7101000313 7838752886 5875332083 8142061717 7669147303 5982534904 2875546873 1159562863 8823537875 9375195778 1857780532 1712268066 1300192787 6611195909 2164201989


Pi \Pi\, v. t. [imp. & p. p. Pied; p. pr. & vb. n. Pieing.] (Print.) To put into a mixed and disordered condition, as type; to mix and disarrange the type of; as, to pi a form. [Written also pie.]



abbr. 1 (context typography English) pica (conventionally, 12 points = 1 pica, 6 picas = 1 inch) 2 piaster 3 pious

  1. (context typography English) Not part of the usual font character set; especially, non-Roman type or symbols as opposed to standard alphanumeric Roman type. n. 1 The name of the sixteenth letter of the Classical Greek and Modern Greek alphabets and the seventeenth in Old Greek. 2 (context mathematics English) An irrational and transcendental constant representing the ratio of the circumference of a Euclidean circle to its diameter; approximately 3.1415926535897932384626433832795; usually written π. 3 (context metal typesetting English) Metal type that has been spilled, mixed together, or disordered. Also called pie. v

  2. (context metal typesetting English) To spill or mix printing type. Also, "to pie".



  1. n. the ratio of the circumference to the diameter of a circle [syn: 3.14159265358979323846...]

  2. someone who can be employed as a detective to collect information [syn: private detective, private eye, private investigator, operative, shamus, sherlock]

  3. the scientist in charge of an experiment or research project [syn: principal investigator]

  4. the 16th letter of the Greek alphabet

  5. an antiviral drug used against HIV; interrupts HIV replication by binding and blocking HIV protease; often used in combination with other drugs [syn: protease inhibitor]

Longman Dictionary of Contemporary English


▪ A broken networked intelligence may be able to calculate pi to the billionth digit but not forward e-mail to a new address.
▪ Consider a symmetric equilibrium in which the n firms in industry i all charge a price pi.
▪ Now came the pi ce de r sistance.
▪ One of his most popular miracles occurred one day while pi owing.
Douglas Harper's Etymology Dictionary


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).

Usage examples of "pi".

Sugar had had their share of beefs in the past, in the three years since his retirement from the Dempsy PD he had become a first-rate gagger, one of a rarefied breed of PIs who, by creating dozens of false identities for themselves over the phone, could assemble a portfolio as thick as the Bible on anyone living or dead, without ever having to leave their apartment.

An elevator whisked him up to the thirtieth floor, and he was soon at the cherry doors leading into the offices of Marcus Hauser, PI.

The remainder, the surrounding curvature, which in some ethereous, immaterial way refused to be rationalized by means of the calculable bounding lines, that, Lawyer Paravant said, with quivering jaw, was pi.

Joseph Blaine hated prolixity almost as much as he hated Napoleon Buonaparte, yet this extreme curtness perplexed Stephen until, recalling times past, he turned the halfsheet over and there on the lower left-hand corner found the faintly-pencilled letter pi, signifying many.

A fine, digital, incredibly wide watch, about five times the width of your wrist, so you have to hold it like a falconer, and it treats time like pi.

He perfected the science of latitude and longitude, determined the value of pi, revolutionized the armillary sphere, and constructed kites that could carry men through the air for long distances.

Voltaire, has been wrong in accusing me of having criticized that tragedy, and in attributing to me an epigram, the author of which has never been known, and which ends with two very poor lines: "Pour avoir fait pis qu'Esther, Comment diable as-to pu faire" I have been told that M.

Ahead, Calis, Sho Pi, Luis, and Jadow crept along, looking for the sentries they knew must be there.

Two commas crossed, an S reversed, an hourglass on its side and pushed inward from the ends, and a crooked pi.

Corbell dialed a number he remembered: two commas crossed, S reversed, hourglass on its side, crooked pi.

Was it rationalization to suggest that the adding machines could not readily multiply or divide numbers, do specialized conversions, or figure the cube root of pi?

This great serpent, this incalculable dragon, was pi, a transcendental number, yielding, when expressed in decimal notation, an infinite table of random numbers.

But so determin'd I was to continue doing a sheet a day of the folio, that one night, when, having impos'd my forms, I thought my day's work over, one of them by accident was broken, and two pages reduced to pi, I immediately distributed and compos'd it over again before I went to bed.

Nkrumah Fubar was experimentally placing a voodoo doll of the president of American Express inside a tetrahedron—their computer was still annoying him about a bill he'd paid over two months ago, on the very daynight that Soapy Mocenigo dreamed of Anthrax Leprosy Pi.

Nkrumah Fubar was experimentally placing a voodoo doll of the president of American Express inside a tetrahedron— their computer was still annoying him about a bill he'd paid over two months ago, on the very daynight that Soapy Mocenigo dreamed of Anthrax Leprosy Pi.