sigma
Americannoun
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the 18th letter of the Greek alphabet: Σ, σ, ς.
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the consonant sound represented by this letter.
noun
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the 18th letter in the Greek alphabet (Σ, σ, or, when final, ς), a consonant, transliterated as S
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maths the symbol Σ, indicating summation of the numbers or quantities indicated
Etymology
Origin of sigma
First recorded in 1600–10; from Latin, from Greek sígma
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
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
But it is much more than the one sigma result of 68% the team obtained 18 months ago,, which was greeted with much scepticism at the time.
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
At the time, the discrepancy between theory and experiment was, in particle-physics parlance, 4.2 sigma.
From Scientific American ● Aug. 10, 2023
For example, what business has the letter rho in the word katoptron, or the letter sigma in the word sphigx?
From Cratylus by Benjamin Jowett
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
