Σ

Sigma in a capital letter Etymologicum Magnum (1499).

Sigma (uppercase Σ, lowercase σ [in final position ς]; called in ancient Greek σῖγμα sîgma /sîːŋ.ma/, in Modern Greek σίγμα sígma /ˈsiɣ.ma/) is the eighteenth letter of the Greek alphabet. The lowercase sigma has two forms: at the end of a word, the form ς is used; at the beginning and in the middle of the word the form σ is used.

In the Greek language, the phonemes [s] and [ʃ] are considered interchangeable. Also, in modern Greek, like other letters of the alphabet, Σ features allophony. When this letter precedes any of the consonants β, γ, δ, μ, ν, ρ, adopts the phoneme [z] (alveolar fricative voiced). In some cases, it takes on this sound when it precedes the letter λ.

In the Greek numeral system it has a value of 200 (Σʹ).

History

The form in zig-zag of sigma (σ) and its position in the alphabet derive from the lyric fenicia shin (). However, it appears broken with respect to its Phoenician model (like other Greek letters such as alpha, gamma or lambda), in addition to ancient epigraphs it appears with a variable number of segments. Sometimes their angles are rounded as in the letter S latina.

The original name of sigma may have been "san", but due to the complicated early history of the Greek epical alphabets, "san" became identified as a separate letter in the Greek alphabet, represented as.. According to Herodoto, the dorians called "san" to the same letter called "sigma" by the jonios. In some archaic alphabets there appeared no sigma, but it was Saint (.) who fulfilled his function, among them were those of Corinth, Etolia, Epiro and Crete. Because in these alphabets it was not sigma, its angulous form was sometimes used for iota (); while to differentiate my from San, my appearance with the legs of different size ().

Regarding the name, "sigma" can continue the name of the letter fenicia samekh (), the lyrics continued in the Greek as φ with the new name "xi". Another theory would be that the name may have been simply a Greek innovation from the verb 'sying', from the root in ancient Greek, σεγ (Yeszōof the *sig-jō 'siseo'.

Epigraphic variants

In archaic epigraphic sources the following variants appear:

Moon Sigma

The most used crystogram in Eastern Europe is ις̄ χς̄ (iota, sigma, ji, sigma),.ησο.ς φστ.ς, which uses the lunad sigma. Often accompanied by a victory, which forms the phrase "Jesus Christ overcomes".

In Greek manuscript from the Hellenistic period (4th–3rd century BC), the epigraphic form of Σ was simplified to a C, which has also been found on coins from the IV a. This became the universal standard form of sigma during late antiquity and the Middle Ages.

From modern times, mostly abandoned, it is known as lunate sigma (uppercase Ϲ, lowercase ϲ), due to its crescent shape, though it is still widely used in decorative lettering in Greece, especially in religious contexts and ecclesiastical, as well as in some modern printed editions of classical Greek texts.

The dotted lunate sigma (sigma peristigmenon, Ͼ) was used by Aristarchus of Samothrace (220-143 BC) as an editorial sign to indicate that the line marked as such is in a wrong position. Similarly, an inverted sigma (antisigma, Ͻ), marks a line out of place. A dotted antisigma (antisigma peristigmenon, Ͽ) indicates a line after which rearrangements must be made, or to variant readings of uncertain priority.

The forms of the letter of the Coptic alphabet "sima" (Ⲥ; 2nd century BC) and the Cyrillic alphabet "es" (С; IX century AD) derive from the lunate sigma.

Use

In the Greek numeral system it has a value of 200 (σʹ).

The capital letter Σ is used as a symbol for:

• Submit.
• A certain alphabet of a language, or another object dependent on an alphabet. Expressed in mathematical terms, e.g., "the language defined by the alphabet σ = {a, b, c}".

The lowercase σ is used as a symbol for:

• Standard deviation
• Variance (σ2)
• Electrical conductivity
• Constant Stefan-Boltzmann
• Sigma function
• Surface load density
• Transcriptional sigma of RNApolimerasa in Bacteria
• Tensor of tensions (σ)
• Normal tension
• Surface tension
• Link sigma
• Replacement elasticity (Microeconomics)

Unicode

• Greek

• Copt

• Maths