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
With the time-lapse microscopy, they tracked expression of a protein, the alternative sigma factor RpoD4.
From Science Daily ● Nov. 25, 2024
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
Take colour, for instance; and we shall perceive that in the Dromius sigma, Rossi, it is sensibly affected.
From On the Variation of Species, with Especial Reference to the Insecta ; Followed by an Inquiry into the Nature of Genera by Thomas Vernon Wollaston
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.
