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[sig-muh] /ˈsɪg mə/
the 18th letter of the Greek alphabet: Σ, σ, ς.
the consonant sound represented by this letter.
Origin of sigma
1600-10; < Latin < Greek sígma Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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British Dictionary definitions for sigma


the 18th letter in the Greek alphabet (Σ, σ, or, when final, ς), a consonant, transliterated as S
(maths) the symbol Σ, indicating summation of the numbers or quantities indicated
Word Origin
Greek, of Semitic origin; related to Hebrew samekh
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for sigma

18th letter of the Greek alphabet, corresponding to Latin S, a metathesis of Hebrew samekh. In uncial writing, shaped like an S or a C.

Online Etymology Dictionary, © 2010 Douglas Harper
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sigma in Medicine

sigma sig·ma (sĭg'mə)

Symbol ς The 18th letter of the Greek alphabet.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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sigma in Science
A sigma baryon.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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sigma in Technology

A scientific visual programming environment from NASA.
The Free On-line Dictionary of Computing, © Denis Howe 2010
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