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

Despite this, the combination of data from all three radio telescopes revealed a deviation exceeding five sigma, a statistically very strong signal considered in science as evidence for a significant result.

From Science Daily • Nov. 22, 2025

"Slay", "sigma" and "skibidi" were chosen as the top three slang words, which OUP said demonstrated the role of social media in influencing children's vocabulary.

From BBC • Jan. 22, 2025

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

From Salon • Oct. 14, 2023

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

From Scientific American • Aug. 10, 2023

In the face of the church, a semicircular portico, of the figure and name of the Greek sigma, was supported by fifteen columns of Phrygian marble, and the subterraneous vaults were of a similar construction.

From History of the Decline and Fall of the Roman Empire — Volume 5 by Milman, Henry Hart