Daily Word Box

Install Daily Word Box: tap Share, then Add to Home Screen.

Word

sigma

noun B2
/ˈsɪɡmə/

Meanings

noun

the 18th letter of the Greek alphabet (Σ, σ)

sigma: the 18th letter of the Greek alphabet (Σ, σ)
noun

a symbol (Σ) meaning the sum of a set of numbers in mathematics

sigma: a symbol (Σ) meaning the sum of a set of numbers in mathematics
noun

a symbol (σ) used in statistics, often for standard deviation

sigma: a symbol (σ) used in statistics, often for standard deviation

Definition

Sigma is the 18th letter of the Greek alphabet, written as Σ or σ.

Sigma is a Greek letter used in mathematics, science, and statistics. You often see it as a capital Σ for “sum” and as a lowercase σ for “standard deviation” or other variables. It is also used to represent the “sigma” sound in Greek spelling systems.

Examples

  • In the formula, sigma tells you to add all the values in the list.
  • She wrote sigma in her notes to remind herself it was a Greek letter.
  • They used sigma to represent the standard deviation in their report.
  • I always confuse sigma with other Greek letters when I read equations quickly.

Common mistake

Learners often mix up sigma (Σ/σ) with similar-looking symbols and use it in a formula where a different variable is intended.

More at B2 level

More nouns