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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