The eighteenth letter of the Classical and Modern Greek alphabets, the twentieth letter of Old and Ancient. / (mathematics) The symbol Σ, used to indicate summation of a set or series.

plural of sigma

(chemistry) A covalent atomic bond that is rotationally symmetric about its axis.

a set of techniques and tools for process improvement.

The form of the Greek letter sigma used in Medieval Greek and occasionally in Greek Orthodox Church transcriptions: ϲ.

plural of final sigma

plural of lunate sigma

The form of the Greek letter sigma only ever used as the last letter of a word: ς.

(mathematical analysis) Alternative form of σ-additivity

A male that occupies outside a social or group hierarchy; a lone wolf or maverick.