Sigma (letter)

Sigma (letter)[EXTRACT]

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Greek alphabet Α α Alpha Β β Beta Γ γ Gamma Δ δ Delta Ε ε Epsilon Ζ ζ Zeta Η η Eta Θ θ Theta Ι ι Iota Κ κ Kappa Λ λ Lambda Μ μ Mu Ν ν Nu Ξ ξ Xi Ο ο Omicron Π π Pi Ρ ρ Rho Σ σ ς Sigma Τ τ Tau Υ υ Upsilon Φ φ Phi Χ χ Chi Ψ ψ Psi Ω ω Omega obsolete letters Digamma San Qoppa Sampi

For other senses of the word "sigma" and other uses of the letter sigma itself, see sigma.

Sigma (upper case Σ, lower case σ, lowercase in word-final position ς) is the 18th 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 upper case, the final form (ς) is used.

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

In Eastern forms of Greek writing (used in the European Greek colonies) and in the Middle Ages, the lunate sigma (upper case C, lower case ϲ) — which resembles like 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, for example, where, for example, the whole of God's creation may be denoted by the word ΚΟCΜΟC ("cosmos"), which in the modern form of writing Greek would be ΚΟΣΜΟΣ.

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Science

Upper case Σ is used as a symbol for ...

• the summation operator
• a class of baryons in particle physics

Lower case σ is used for ...

• the parametric standard deviation of a population (as opposed to a sample) in statistics
• the divisor function in number theory
• the Stefan-Boltzmann constant
• the "sigma factor" of RNA polymerase
• a measure of electrical conductivity

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Popular culture

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

Retrieved from "http://en.wikipedia.org/wiki/Sigma_%28letter%29"

Category: Greek letters