sigmata

Noun

sigma (plural sigmas or sigmata)

1. 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
2. The symbol Σ, used to indicate summation of a set or series.
3. The symbol σ, used to indicate one standard deviation from the mean, particularly in a normal distribution.
   • 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.2011, Paul Rincon, (bbc.co.uk) LHC: Higgs boson 'may have been glimpsed'
4. (Internet) A sigma male (a self-reliant and assertive male).

See all 6 meanings of sigma