Sigma

.

Sigma as a letter in the Greek alphabet (Σ, σ, or ς) may refer to many things:

Upper-case letter Σ is used as a symbol for

• the summation operator forming a series in mathematics.
  
• a certain alphabet of a language, or of some other object dependent on an alphabet; expressed in mathematical terms, eg "the language defined by alphabet Σ={a,b,c} and the rules ..."
  
• The lower-case letter σ is used as a symbol for
  
• the standard deviation of a population in statistics.
  
• the divisor function in number theory.
  
• the Stefan-Boltzmann constant of radiation in physics.
  
• the Sigma factor of RNA polymerase in biology.
  

Sigma can also refer to:

• a classification of quantum particle—see baryon.
  
• cell receptors in biochemistry and pharmacology.
  
• the name (Sigma) of the main villain from the video game series Mega Man X.
  
• a manufacturer (Sigma Corporation) of cameras, lenses and camera accessories.
  
• Sigma Designs, a company manufacturing ASICs for digital video appliances.
  
• a model of handgun manufactured by Smith and Wesson.
  
• a series of sailing yachts.
  
• the Mitsubishi Sigma, a variant of the Mitsubishi Galant.
  
• SIGMA (verification service), Nielsen Media Research's tracking system that allows Nielsen to electrionically monitor airplay of videos.
  
• the name of an insurance company active in Albania.
  
• Sigma, Capiz, a municipality in the Philippines.
  
• Sigma refers informally to the degree of exceptionality of a person or thing.
  
• Six Sigma is a quality management program; the name refers to six standard deviations.
  

As an acronym SIGMA can stand for the Society of Independent Gasoline Marketers of America.

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 Sigma
Τ τ Tau	Υ υ Upsilon	Φ φ Phi
Χ χ Chi	Ψ ψ Psi	Ω ω Omega

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