The Open Dictionary

sigma

noun

UK/ˈsɪɡ.mə/
US/ˈsɪɡ.mə/

Definitions of sigma noun

  1. CountableUncountablelanguage

    the eighteenth letter of the Greek alphabet, represented as σ (lowercase) or Σ (uppercase).

    • In mathematical formulas, Σ is often used to denote a sum.

    • The lowercase letter σ is used to denote standard deviation in statistics.

    • In physics, sigma (σ) might represent conductivity.