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Biography
Other usesFor|the cedilla |çRedirect|S|the Latin character|Esh (letter)Wiktionary|S|s|?Greek Alphabet|letter=sigma Sigma (upper case S , lower case s , lower case in word-final position ? ; Ancient Greek|Greek s??µa) 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 (?) is used, e.g. unicode|?d?sse?? (Odysseus) – note the two sigmas in the center of the name, and the word-final sigma at the end.
History
Etymology
The name of sigma, according to one theory,cite book|last=Jeffery|first=Lilian H.|title=The local scripts of archaic Greece|place=Oxford|publisher=Clarendon|year=1961|pages=25–27 may continue that of Phoenician Samekh . According to a different theory,cite encyclopedia|encyclopedia=Encyclopedia of ancient Greece|editor-first=Nigel Guy|editor-last= Wilson|title=Alphabet|first=Roger D.| last=Woodard|year=2006| publisher=Routldedge| place=London| page=38 its original name may have been " San (letter)|San " (the name today associated with another, obsolete letter), while "Sigma" was a Greek innovation that simply meant "hissing", based on a nominalization of a verb lang|grc|s??? ( sízo , from earlier * sig-jo , meaning 'I hiss').
Uppercase of esh
The uppercase form of sigma was re-borrowed into the Latin alphabet to serve as the uppercase of modern esh (letter)|esh (lowercase: unicode|?).
Lunate sigma
In handwritten Greek during the Hellenistic period (4th and 3rd centuries BC), the epigraphic form of S was simplified into a C-like shape.Edward M. Thompson (1912), Introduction to Greek and Latin paleography , Oxford: Clarendon. p.108, 144 It is also found on coins from the fourth century BC onwards. http://www.parthia.com/fonts/letterforms_usage.htm Parthia.com: Numismatica Font Projects . This became the universal standard form of Sigma during late antiquity and the Middle Ages. It is today known as lunate sigma (upper case Unicode|?, lower case Unicode|?), because of its crescent -like shape.
It is still widely used in decorative typefaces in Greece, especially in religious and church contexts, as well as in some modern print editions of classical Greek texts. The forms of the Cyrillic script|Cyrillic letter Es (Cyrillic)|? (representing IPA|/s/) and Coptic alphabet|Coptic letter coptic|? sima are derived from lunate sigma.
A dotted lunate sigma ( sigma periestigmenon , encoded at U+03FE unicode|?) was used by Aristarchus of Samothrace as an editorial sign indicating that the line so marked is at an incorrect position. Similarly, an antisigma or reversed sigma (unicode|?) may mark a line that is out of place. A dotted antisigma or dotted reversed sigma ( antisigma periestigmenon : unicode|?) may indicate a line after which rearrangements should be made, or to variant readings of uncertain priority.
Uses
Greek
In both Ancient Greek|Ancient and Modern Greek , the sigma represents the voiceless alveolar fricative IPA|/s/. Both in Ancient and Modern Greek, this sound is voice (phonetics)|voiced to IPA|/z/ before IPA|/m/ or IPA|/n/.
Berber
Upper case S may be used in the Berber Latin alphabet for ?, though the INALCO standard uses ? instead.
Science and mathematics
Upper case
Upper case S is used as a symbol for:
the summation operator
a class of baryon s in particle physics
macroscopic Cross section (physics)|cross section s in nuclear physics|nuclear and particle physics
self-energy in condensed matter physics
the Balance (accounting)|balance of the invoice classes and the overall amount of the debts and demands in economics
the set of symbols that form an alphabet in linguistics and Computer Science|computer science
the covariance matrix of a set of random variables in probability theory and statistics , sometimes in the form to distinguish it from the summation operator.
Lower case
Lower case s is used for:
sigma bond s in chemistry
Sigma constant in science
the sigma receptor in biology
the standard deviation of a Standard deviation#Estimating_population_standard_deviation|population or probability distribution in statistics
a quality model for business, Six Sigma , based on the standard deviation , often referred to as " 6s "
sigma-algebra s, sigma-fields and Sigma-finite measure|sigma-finiteness in Measure (mathematics)|measure theory ; more generally, the symbol s serves as a shorthand for " countable set|countably ", e.g. a s -compact topological space is one that can be written as a countable union (set theory)|union of compact space|compact subsets .
the Sigma-algebra#Generated_.CF.83-algebra|generated sigma-algebra of a set is denoted
the divisor function|sum-of-divisors function in number theory
the Stefan–Boltzmann constant
the " sigma factor " of RNA polymerase
a measure of electrical conductivity
the Surface charge density in electrostatics
Normal stress|Normal Stress (physics)|stress in continuum mechanics
volatility of a stock generally needed for options pricing
a syllable in phonology
the spectrum of a matrix , denoted as , in applied mathematics
surface tension
the unary operation of Selection (relational algebra)|selection on a database relation in relational algebra
the Pauli matrices in quantum mechanics
a target's radar cross-section (RCS) in radar jamming or Electronic warfare|Electronic Warfare (EW)
the Sigma (bone remodeling)|life span of a basic multicellular unit (BMU) in bone remodeling
the Damping Parameter in Signal processing
a millisecond in early 20th century physiology literaturecite doi|10.1038/136222a0.
Politics
During the 1930s, an upper case S was in use as the symbol of the Brazilian Integralism|Açăo Integralista Brasileira , a radical right-wing party in Brazil .
Technical notes
Unicode
description !! character !! Unicode !! HTML
Greek
SIGMA
SMALL LETTER FINAL SIGMA
LUNATE SIGMA SYMBOL
REVERSED LUNATE SIGMA SYMBOL
DOTTED LUNATE SIGMA SYMBOL
REVERSED DOTTED LUNATE SIGMA SYMBOL
There are several Unicode codepoint s representing the Greek letter sigma.
The use of multiple codepoints for final / non-final sigma is somewhat unusual in Unicode. However, the two cannot always be distinguished by a simple algorithm (there are exceptions for abbreviations), and there is a significant history of them being separate characters in other specifications. http://unicode.org/faq/greek.html#5 Unicode.org
Additionally, there are at least 23 codepoints for sigma as a symbol (bold, italic, sans-serif, lunate, reversed, or dotted, in various combinations).
See also
Antisigma
Greek letters used in mathematics, science, and engineering
