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.
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
"Our work shows that the dark photon hypothesis is preferred over the standard model hypothesis at a significance of 6.5 sigma, which constitutes evidence for a particle discovery."
From Science Daily ● Sep. 18, 2023
At the time, the discrepancy between theory and experiment was, in particle-physics parlance, 4.2 sigma.
From Scientific American ● Aug. 10, 2023
Sigmoid: shaped like the Greek letter sigma, or English S.
From Explanation of Terms Used in Entomology by John. B. Smith
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.
