Sigma

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For other uses, see Sigma (disambiguation).

Look up Σ, σ, ς in Wiktionary, the free dictionary.

Greek alphabet

Αα Alpha	Νν Nu
Ββ Beta	Ξξ Xi
Γγ Gamma	Οο Omicron
Δδ Delta	Ππ Pi
Εε Epsilon	Ρρ Rho
Ζζ Zeta	Σσς Sigma
Ηη Eta	Ττ Tau
Θθ Theta	Υυ Upsilon
Ιι Iota	Φφ Phi
Κκ Kappa	Χχ Chi
Λλ Lambda	Ψψ Psi
Μμ Mu	Ωω Omega
Obsolete letters
Digamma	Qoppa
San	Sampi

Greek diacritics

The Madaba Map, a sixth-century mosaic map of Jerusalem ("ΗΑΓΙΑ ПОΛΙΣ") uses the lunate sigma.

Sigma (upper case Σ, lower case σ, lower case in word-final position ς) is the eighteenth letter of the Greek alphabet. In the system of Greek numerals it has a value of 200. When used at the end of a word, and the word is not all upper case, the final form (ς) is used. (e.g. Ὀδυσσεύς (Odysseus) - Note the two sigmas in the center of the name, and the word-final sigma at the end.) Not to be confused with the cedilla ç.

The letter is ultimately derived from Phoenician Šin 𐤔. However, its name derives from Samekh.

The uppercase form of sigma was borrowed into the Latin alphabet to serve as the uppercase of esh (lowercase: ʃ).

1 Lunate sigma
2 Science and mathematics
3 Politics
4 Popular culture and use in fiction
5 See also

[edit] Lunate sigma

In Eastern forms of Greek writing (as opposed to the Western Greek alphabet used in the European Greek colonies) and in the Middle Ages, the lunate sigma (upper case Ϲ, lower case ϲ) — which resembles, but which is not at all related to, the Latin letter C — was often used. Lunate sigma was frequently used for writing Medieval Greek, and it can still sometimes be seen in inscriptions in Greek Orthodox churches, but also in certain printed editions of classical authors. The form of the Cyrillic letter С [s] and Coptic letter sima are derived from lunate sigma.

On coins from the Hellenistic period in India, the script of later coins sometimes use lunate sigma. This sigma continued to be written this way also in Medieval Greek.

A dotted lunate sigma (sigma periestigmenon, encoded at U+03FE Ͼ) is used by Aristarchus of Samothrace as an editorial sign indicating that the line so marked is at an incorrect position. Similarly, an antisigma (encoded at U+03FD Ͻ) may mark a line that is out of place. A dotted antisigma (antisigma periestigmenon, encoded at U+03FF Ͽ) may indicate a line after which rearrangements should be made, or to variant readings of uncertain priority.

[edit] Science and mathematics

Upper case Σ is used as a symbol for:

the summation operator
a class of baryons in particle physics
macroscopic cross sections in nuclear and particle physics
in economics this letter is for the balance of the invoice classes, the overall amount of the debts and demands
in linguistics and computer science it is used to refer to the set of symbols that form an alphabet

Lower case σ is used for:

sigma bonds in chemistry
the parametric standard deviation of a population (as opposed to a sample) in statistics
a quality model for business, Six Sigma, based on the standard deviation, often referred to as "6σ"
sigma-algebras, sigma-fields and sigma-finiteness in measure theory; more generally, the symbol σ serves as a shorthand for "countably", e.g. a σ-compact topological space is one that can be written as a countable union of compact subsets.
the sum-of-divisors function in number theory
the Stefan-Boltzmann constant
the "sigma factor" of RNA polymerase
a measure of electrical conductivity
Normal stress in continuum mechanics
volatility of a stock generally needed for options pricing
a syllable in phonology
the spectrum of a matrix $A$ , denoted as $σ(A)$ , in applied mathematics
surface tension
In relational algebra sigma is used to define the unary operation selection on a database relation.

[edit] Politics

During the 1930s, an upper case Σ was in use as the symbol of the Ação Integralista Brasileira, a radical right-wing party in Brazil.

[edit] Popular culture and use in fiction

In a practice similar to faux Cyrillic, capital sigmas are sometimes used in place of Roman E to give a Greek flavour to titles or text (for example, the film My Big Fat GRΣΣK Wedding).

Sigma is the name of the main villain in Capcom's Mega Man X. His symbol is an upper-case sigma formed into a wolf's face.

Sigma Octanus IV is a fictional planet in the Halo books.

Sigma is the name of the fourth server in the .hack video game series.

Mercury-Atlas 8 was called Sigma 7.

Sigma is a measure of male sexual arousal coined by the character Lawrence Waterhouse in Neal Stephenson's Cryptonomicon

The latest edition of the Ninja Gaiden video game series is titled Ninja Gaiden Sigma, was released on the Playstation 3 in July 2007 in North America.

In the television series Doctor Who, Theta Sigma is the nickname of the Doctor, given by his classmates on Gallifrey. Sigma was also the designation of an Ood alien in the episode Planet of the Ood.

Japanese electro-pop musician Hirasawa Susumu has a song called "Fern of the Planet Sigma" in his "Byakkoya" ("White Tiger Field") album from 2006.

The current GI Joe incarnation is entitled G.I. Joe: Sigma 6.
Sigma is the name of a song from Japanese singer Shiina Ringo.

Sigma is the title of a 2007 album by eufonius.

The Sigma Protocol is a 2002 book by Robert Ludlum.

Sigma Shipyards is the name of a corporation in the Escape Velocity Nova computer game.

Vector Sigma is the Computer matrix that created the cybertronian lifeforms the Transformers in the popular cartoon series from the 1980s

Sigma is used in the latter (Chris Redfield) half of survival-horror game Resident Evil Code: Veronica in which you much retrieve 'Clement a ' and 'Clement Σ'
Sigma 2,3,5,6,7,8,9 Computers produced by Xerox Data Systems in the 1970s following purchase of SDS, Scientific Data Systems by them. Successful range of Scientific Computers similar to IBM 370's.

A firearm series made by Smith & Wesson called Sigma or VE. The firearm is available in .40 S&W and 9x19mm

Sigma is the name of a system for ontology development and reasoning

In a season 3 episode of the Disney Channel show That's So Raven, entitled "Members Only", Eddie wishes to join a group in the school named the Sigmas. The Sigmas are the most popular group in their school, and all of the members wore yellow jackets with an uppercase Sigma on the left breast.

There is a sorority named Sigma Sigma Sigma

Phi Sigma Alpha Fraternity goes by the name of Sigma Fraternity.

There are nine historically Black Greek letter organizations (BGLOs) that make up the National Pan-Hellenic Council. Collectively, these organizations are referred to as "The Divine Nine." Phi Beta Sigma Fraternity, Inc., an international organization of college and professional men, was founded on January 9, 1914. Members of Phi Beta Sigma are known as SIGMAS. Members of Sigma Gamma Rho Sorority also often referred to themselves and each other as Sigmas.

In the Earthbound, or Mother, series of Nintendo RPG games by Shigesato Itoi, Σ (along with other Greek letters) is used as a classification of the strength of a PSI technique.

Sigma refers to a peak state of consciousness when a user of dextromethorphan hydrobromide consumes a near deadly dosage.

Chrysler released a Rear wheel drive 4 door sedan in 1979 named GE Sigma, later manufactured by Mitsubishi

Sigma Xi, The Scientific Research Society, was founded 1886 at Cornell University as an honor society for scientists and engineers.

Sigma Zeta, The honor society for undergraduate science, math, and computer science founded at Shurtleff College in Alton, Illinois, in the autumn of 1925.