Sigma

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Greek alphabet
[[Image:Greek alphabet {{{letter\|alpha-omega}}}.png\| 200px\|center]]
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
Image:Greek alphabet digamma2.png Digamma	Image:Greek alphabet san.png San
Image:Greek alphabet qoppa.png Qoppa	Image:Greek alphabet sampi.png Sampi
Image:Greek alphabet stigma.png Stigma	Image:Greek alphabet sho.png Sho

For other uses, see Sigma (disambiguation).

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 Image:Phoenician sin.png. 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, 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, 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. The form of the Cyrillic letter С [s] comes from this usage.

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