1
: the 18th letter of the Greek alphabet see Alphabet Table
3
slang
: a person who is coolly self-assured, independent, and driven
Unlike alpha males and females who thrive on social dominance, sigmas prefer solitude and operate outside of traditional social hierarchies.—
Gayathri Kallukaran
—often used before another nounGayathri Kallukarana sigma male/female
Examples of sigma in a Sentence
Recent Examples on the Web
The company has made innovations in write assist, stability assist, pioneering high-sigma design modeling to capture tail bits and row plus column redundancy to enable low voltages and high overall yields.
—Thomas Coughlin, Forbes.com, 3 Sep. 2025
The consequences are fatal, and the silence and sigma surrounding it has become part of the problem.
—Sreedhar Potarazu, Baltimore Sun, 6 July 2025
This is a figure known as five sigma, which equates to about a one in a million chance that the findings are a fluke.
—Oliver Swainston, Space.com, 28 June 2025
While the signal is there at three sigma, that's three sigma above a completely featureless spectrum.
—John Timmer, ArsTechnica, 17 Apr. 2025
The current findings are between 2.8 and 4.2 sigma, yet each new round of data brings the DESI team closer to rewriting the understanding of dark energy and sending cosmologists back to their blackboards to invent new theories about the laws of the universe.
—Chase Hunter, Mercury News, 1 Apr. 2025
The confidence level ranges from 2.8 to 4.2 sigma, depending on the combination of datasets—just shy of the five-sigma threshold.
—Jennifer Ouellette, Ars Technica, 19 Mar. 2025
According to the group’s calculations, the Planck data point to a closed universe with a standard deviation of 3.5 sigma (a statistical measurement that means about 99.8% confidence that the result isn’t due to random chance).
—Rafi Letzter, Scientific American, 5 Nov. 2019
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Thomas Coughlin, Forbes.com, 3 Sep. 2025
The consequences are fatal, and the silence and sigma surrounding it has become part of the problem.
—Sreedhar Potarazu, Baltimore Sun, 6 July 2025
This is a figure known as five sigma, which equates to about a one in a million chance that the findings are a fluke.
—Oliver Swainston, Space.com, 28 June 2025
While the signal is there at three sigma, that's three sigma above a completely featureless spectrum.
—John Timmer, ArsTechnica, 17 Apr. 2025
The current findings are between 2.8 and 4.2 sigma, yet each new round of data brings the DESI team closer to rewriting the understanding of dark energy and sending cosmologists back to their blackboards to invent new theories about the laws of the universe.
—Chase Hunter, Mercury News, 1 Apr. 2025
The confidence level ranges from 2.8 to 4.2 sigma, depending on the combination of datasets—just shy of the five-sigma threshold.
—Jennifer Ouellette, Ars Technica, 19 Mar. 2025
According to the group’s calculations, the Planck data point to a closed universe with a standard deviation of 3.5 sigma (a statistical measurement that means about 99.8% confidence that the result isn’t due to random chance).
—Rafi Letzter, Scientific American, 5 Nov. 2019
Cite this Entry
“Sigma.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/sigma. Accessed 22 Oct. 2025.
Copy CitationKids Definition
sigma
noun
sig·ma
ˈsig-mə 
: the 18th letter of the Greek alphabet
—Σ or σ or ς
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