sigma

American  

[sig-muh] / ˈsɪg mə /

noun

1. the 18th letter of the Greek alphabet: Σ, σ, ς.

2. the consonant sound represented by this letter.

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sigma British  

/ ˈsɪɡmə /

noun

1. the 18th letter in the Greek alphabet (Σ, σ, or, when final, ς), a consonant, transliterated as S

2. maths the symbol Σ, indicating summation of the numbers or quantities indicated

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sigma Scientific  

/ sĭg′mə /

1. A sigma baryon.

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Etymology

Origin of sigma

First recorded in 1600–10; from Latin, from Greek sígma

Example Sentences

These latest results are only three sigma, 99.7%.

From BBC • Apr. 16, 2025

If you’re lurking in dark corners of the internet, there’s alpha, beta and sigma males.

From Salon • Oct. 14, 2023

One is a putative chitobiase that the UAB researchers found was located next to genes encoding SusD, SusC, putative anti-sigma factor and RNA polymerase ECF-type sigma factor.

From Science Daily • Oct. 13, 2023

At the time, the discrepancy between theory and experiment was, in particle-physics parlance, 4.2 sigma.

From Scientific American • Aug. 10, 2023

Record, average time, in sigma, and number of false reactions.

From Vocational Psychology: Its Problems and Methods by Hollingworth, Harry L.