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.
Sigma, valued at US$21.5 billion, agreed to launch its Chemist Warehouse brand in the U.K. with Greenlight Healthcare.
From The Wall Street Journal • Jun. 14, 2026
SYDNEY—Australia’s Sigma Healthcare SIG -1.86%decrease; red down pointing triangle withdrew its interest in acquiring Boots, saying a deal for the U.K. drugstore chain wouldn’t meet its strategic or capital-investment objectives.
From The Wall Street Journal • Jun. 14, 2026
Sigma said it remained committed to driving growth in what it called its core offshore markets.
From The Wall Street Journal • Jun. 14, 2026
Deviation, the firm that Two Sigma Ventures became when it was spun out of hedge fund Two Sigma, has long backed startups in the Bay Area.
From The Wall Street Journal • Jun. 1, 2026
Members of the newly formed all-black Delta Sigma Theta sorority of Howard College also joined the procession, knowing that if they didn’t stand up for their rights, African American women would undoubtedly be left behind.
From "1919 The Year That Changed America" by Martin W. Sandler
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.
