# Sigma (disambiguation)

Sigma (Σ or σ, word-final lowercase ς) is the 18th letter of the Greek alphabet.
Sigma may also refer to:

## Companies and organizations

* Sigma AB, a Swedish IT consultancy company
* Sigma Alimentos, multinational food processing and distribution company
* Sigma Corporation, a Japanese camera and lens manufacturer
* Sigma Designs, Inc., a US semiconductor manufacturer
* Sigma Guitars, a guitar manufacturing brand
* Sigma Healthcare, an Australian pharmaceutical company
* Sigma Motor Corporation, a defunct South African motor vehicle assembler and manufacturer
* Sigma Motors, a Pakistani assembler of Land Rovers
* Sigma Sigma Sigma (Tri-Sigma), an American women's sorority centered on education & scholarship
* Sigma Sport, a German manufacturer of electronic sports equipment
* SIGMA (Support for Improvement in Governance and Management), a joint initiative of the OECD and the European Union
* Sigma TV, a television channel in Cyprus
* Sigma (operations research), a company founded in the UK in 1961
* SIGMA (verification service), Nielsen Media Research's tracking system for videos
* Sigma-Aldrich, an American chemical company
* Telkomsigma or Sigma Cipta Caraka, an Indonesian IT company

## Films and television

* Ood Sigma, a fictional character from the Doctor Who series
* Space City Sigma, a 1980s Indian science fiction TV series
* Sigma, a fictional character from the anime Tweeny Witches
* Sigma Society, a fictional Mensa-type club, appearing in the third episode of Columbo sixth season
* Sigma, a fictional character from the Bungo Stray Dogs manga and anime series

## Mathematics

* Summation operator forming a series in mathematics Σ
* Standard deviation in statistics σ
* Divisor function in number theory σ
* Sigma-algebra (σ-algebra, σ-field) in set theory
* A busy beaver function in computability theory Σ
* $\Sigma _{n}^{0}$ or $\Sigma _{n}^{1}$, sets in the analytical hierarchy
* $\Sigma _{i}^{P}$, a set in the polynomial hierarchy
* Harish-Chandra's σ function
* Weierstrass sigma function
* Sigma additivity

## Music

* Sigma (album)
* Sigma (DJs), a British drum and bass duo
* Sigma AZ (band), punk rock band from Phoenix, Arizona
* Universal Sigma, a Japanese record label under Universal Music Japan
* Sigma Boy, a 2024 single by Betsy and Maria Yankovskaya

## Places

* Sigma, Capiz, a municipality in the Philippines
* Sigma, Lee County, Virginia, an unincorporated community in the United States
* Sığma, Sarayköy, a neighbourhood of the municipality and district of Sarayköy, Denizli Province, Turkey

## Products

* GM Sigma platform, an automobile platform
* Mitsubishi Sigma, a model name used for various automobiles produced by Mitsubishi
* Chrysler Sigma, a version of the Mitsubishi Galant sold in Australia
* Ferrari Sigma, also known as the Pininfarina Sigma, a Formula 1 show car
* Ford Sigma engine, a series of straight four engines
* SDS Sigma series of computers from Scientific Data Systems
* Sigma (sailplane), an experimental glider developed in Britain from 1966
* Six Sigma quality management program
* Smith & Wesson Sigma, a firearm

## Science

* σ, sigma bond in chemistry
* σ, sigma factor of RNA polymerase in biology
* σ, Stefan–Boltzmann constant of radiation in physics
* σ, stress (mechanics), the force per unit area applied by internal forces of a material
* σ, the electronic substituent constant for activation of substituted arenes in the Hammett equation
* σ, a measure of a material's electrical conductivity ability
* Cross section σ in physics
* Pauli matrices in quantum physics
* Sigma baryon in particle physics
* Sigma receptor, a neural receptor
* Surface charge density in classical electromagnetism
* Sigma, a Greek letter used in Bayer designations for naming stars, in astronomy. Notable examples include:
** Sigma Canis Majoris
** Sigma Draconis
** Sigma Octantis
** Sigma Orionis

## Sport

* Sigma FC, a Canadian soccer team
* SK Sigma Olomouc, a Czech association football team
* Histor–Sigma, a Belgian professional cycling team known as Sigma in 1986

## Video games

* Sigma (Mega Man X), the main antagonist of the Mega Man X series
* Sigma (Overwatch), a hero from Overwatch
* Ninja Gaiden Sigma, a video game
* Sigma, a character in the BioShock 2 video game universe
* Sigma Harmonics, a video game
* Sigma Klim, a major character and protagonist in the Zero Escape video game series
* Sigma, a team on the Dota 2 online video game

## Other

* Sigma (couch), used in ancient Roman banquets
* Sigma class corvette, a naval ship
* Sigma male, a slang term for masculine men