Sigma

From Freepedia

Sigma as a letter of the Greek alphabet may refer to many things:

• The letter Sigma (Σ, σ, or ς) itself.
• 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.