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Sigma uc lc.svg
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 uc lc.svg Digamma Qoppa uc lc.svg Qoppa
San uc lc.svg San Sampi uc lc.svg Sampi
Other characters
Stigma uc lc.svg Stigma Sho uc lc.svg Sho
Heta uc lc.svg Heta

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

Sigma (upper case Σ, lower case σ, lower case in word-final position ς; Greek Σιγμα) is the eighteenth letter of the Greek alphabet, and carries the /s/ sound. 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. It is 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).

Disigma, or "double sigma", is a non-current term for the character sampi. [1]


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 can still be seen in inscriptions in Greek Orthodox churches, and 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) was 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.

Science and mathematics

Upper case Σ is used as a symbol for:

Lower case σ is used for:


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.


  • Mercury-Atlas 8 was called Sigma 7.
  • Upper-case Σ is sometimes substituted jocularly for upper-case E to impart a "Greek" air; posters for the film My Big Fat Greek Wedding and promotional materials for the television series Greek, for instance, have "GRΣΣK" instead.
  • 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 it. Successful range of scientific computers similar to IBM 370s.
  • Sigma is the name of a system for ontology development and reasoning
  • Project Sigma was the name of a proposal for a "spontaneous university" by the Scottish writer Alexander Trocchi.
  • The French mathematician and poet Jacques Roubaud used the symbol as a title for his first book of poems, Σ, published in 1967.[1]
  • The main antagonist in the Mega Man X series is named Sigma.
  • In the video game Lux-Pain, Sigma is often mentioned as a power used to destroy "Silent".

See also


  1. ^ Auster, Paul, editor, The Random House Book of Twentieth-Century French Poetry: with Translations by American and British Poets, New York: Random House, 1982 ISBN 0394521978


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