sigma

noun

sig·​ma ˈsig-mə 

plural sigmas

1

: the 18th letter of the Greek alphabet see Alphabet Table

2

: standard deviation

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

I know nowadays, everyone's trying to be a sigma, no one wants to admit any kind of fear …

—Adam Richman

—often used before another noun

a sigma male/female

I'm what's called a sigma personality. I never seek leadership. I fill in where I see a need.

—@imsarahbella, on X (formerly Twitter)

… the two [movies] have the same loner, dark, depressed sigma vibe …

—@3RBlank, on Reddit

compare alpha entry 1 sense 6, beta entry 1 sense 2b

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

Word History

Etymology

Greek

First Known Use

1550, in the meaning defined at sense 1

Rhymes for sigma

• stigma
• enigma
• kerygma

Kids Definition

sigma

noun

sig·​ma ˈsig-mə 

: the 18th letter of the Greek alphabet

—Σ or σ or ς