(redirected from sigmas)
Also found in: Thesaurus, Medical, Acronyms, Encyclopedia.


1. The 18th letter of the Greek alphabet. See Table at alphabet.
2. A sigma factor.
3. Statistics The standard deviation of a given probability distribution or a given set of data.

[Greek sīgma, of Phoenician origin; see smk in Semitic roots.]

sig′mate′ (-māt′) adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


1. (Letters of the Alphabet (Foreign)) the 18th letter in the Greek alphabet (Σ, σ, or, when final, ς), a consonant, transliterated as S
2. (Mathematics) maths the symbol Σ, indicating summation of the numbers or quantities indicated
[Greek, of Semitic origin; related to Hebrew samekh]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈsɪg mə)

n., pl. -mas.
the 18th letter of the Greek alphabet: Σ, σ, ς.
[1600–10; < Latin < Greek sígma]
sig•mate (ˈsɪg mɪt, -meɪt) adj.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.sigma - the 18th letter of the Greek alphabetsigma - the 18th letter of the Greek alphabet
Greek alphabet - the alphabet used by ancient Greeks
alphabetic character, letter of the alphabet, letter - the conventional characters of the alphabet used to represent speech; "his grandmother taught him his letters"
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.


[ˈsɪgmə] nsigma m or f inv
Collins Italian Dictionary 1st Edition © HarperCollins Publishers 1995
References in classic literature ?
The outlying villages, they say, are by them called {kappa omega mu alpha iota}, by the Athenians {delta eta mu iota}: and they assume that Comedians were so named not from {kappa omega mu 'alpha zeta epsilon iota nu}, 'to revel,' but because they wandered from village to village (kappa alpha tau alpha / kappa omega mu alpha sigma), being excluded contemptuously from the city.
Each 6- sigma project is supported by a team with defined responsibilities and follows a defined sequence of steps and has quantified targets.
The third level, 6-sigma as a metric, is the source of the name 6- sigma. 6-sigma refers to 3.4 defects per one million opportunities (DPMO).
Quality in a laboratory is measured on the sigma scale with a criterion of 3 a as the minimum allowable sigma for routine performance and a sigma of 6 a was considered as world-class quality.
We analysed sigma metrics of 13 parameters with autoanalyser EM 360.
"Those that perpetuate the divide between Six Sigma and Lean are clearly missing the point" says Noble.
Six Sigma techniques identify and eliminate variability, increase accuracy and precision, and demand decisions drive by data rather than guesswork and intuition.
Lean Six Sigma techniques integrate risk and document processes.
In statistics, sigma denotes the standard deviation of a set of data.
But, in addition to the natural variation of a process, it has been found that the mean value itself is susceptible to a shift of up to [+ or -] one-and-a-half sigma [ILLUSTRATION FOR FIGURE 2 OMITTED].