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.
The new LZ finding currently sits at 2.6 sigma.
From Science Daily ● Sep. 4, 2026
In scientific jargon that is a five sigma result.
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
Sigmoid, curved in two directions, like the letter S, or the Greek sigma.
From The Elements of Botany For Beginners and For Schools by Asa Gray
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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
