From Ancient Greek σῖγμα (sîgma), probably from the root σῑγ- (sīg-) as seen in σίζω (sízō, “to hiss”) + -μα (-ma, nominal suffix).
Meanings
The eighteenth letter of the Classical and Modern Greek alphabets (Σ, σ), the twentieth letter of Old and Ancient.
Their names, which are expressive of some bodily or mental excellence, all end with the same letter---the letter which is called San by the Dorians, and Sigma by the Ionians. "Herodotus: On The Customs of the Persians", I.139
The symbol Σ, used to indicate summation of a set or series.
The symbol σ, used to indicate one standard deviation from the mean, particularly in a normal distribution.
2011, Paul Rincon, (bbc.co.uk) LHC: Higgs boson 'may have been glimpsed'
None of the spikes seen by the experiments is at much more than the "two sigma" level of certainty.
A level of "five sigma" is required to claim a discovery, meaning there is less than a one in a million chance the data spike is down to a statistical fluke.
(Internet) A sigma male (a self-reliant and assertive male).
ia sigma (letter of the Greek alphabet) · ar سِغْمَا (letter of the Greek alphabet) · he סִיגְמָא (letter of the Greek alphabet) · cmn 西格瑪 /西格玛 (letter of the Greek alphabet) · nl sigma (letter of the Greek alphabet) · ast sigma (letter of the Greek alphabet) · eo sigmo (letter of the Greek alphabet) · es sigma (letter of the Greek alphabet) · cmn 西格馬 /西格马 (letter of the Greek alphabet) · ja シグマ (letter of the Greek alphabet) · de Sigma (letter of the Greek alphabet) · fa سیگما (letter of the Greek alphabet) · ga sigme (letter of the Greek alphabet) · th ซิกมา (letter of the Greek alphabet) · sk sigma (letter of the Greek alphabet) · ko 시그마 (letter of the Greek alphabet) · fr sigma (letter of the Greek alphabet) · ar سِيغْمَا (letter of the Greek alphabet) · mi hikama (letter of the Greek alphabet) · ms sigma (letter of the Greek alphabet) · cs sigma (letter of the Greek alphabet) · acw سِقْما (letter of the Greek alphabet) · ar سِيجْمَا (letter of the Greek alphabet) · ca sigma (letter of the Greek alphabet) · ar سِجْمَا (letter of the Greek alphabet) · fi sigma (letter of the Greek alphabet) · ru си́гма (letter of the Greek alphabet) · sv sigma (letter of the Greek alphabet) · el σίγμα (letter of the Greek alphabet) · gl sigma (letter of the Greek alphabet) · hu szigma (letter of the Greek alphabet) · grc σῖγμα (letter of the Greek alphabet) · pt sigma (letter of the Greek alphabet) · pl sigma (letter of the Greek alphabet)