Σσ Sigma was a letter in the Greek alphabet of Earth, originating in the early period of Human history.
It was used in the following contexts:
- Astronomical nomenclature
- Sigma X, a planet
- Sigma Antares sector
- Sigma Boötis, a star system
- Sigma Ceti, a star system
- Sigma Coronae Borealis, a star system
- Sigma Draconis star system
- Sigma Draconis I, a planet
- Sigma Draconis II, a planet
- Sigma Draconis III, a planet
- Sigma Draconis III native, a species
- Sigma Draconis IV, a planet
- Sigma Draconis V, a planet
- Sigma Draconis VI, a planet
- Sigma Draconis VI native, a species
- Sigma Draconis VII, a planet
- Sigma Draconis VIII, a planet
- Sigma Draconis IX, a planet
- Sigma Erandi system (aka Sigma Erani system)
- Sigma III solar system
- Quadra Sigma III, a planet
- Sigma Iotia, a star system
- Sigma Iotia II, a planet
- Sigma Librae, a star
- Sigma Nelvana, a star
- Sigma Nesterowitz, a location
- Sigma Pegasi, a star system
- Sigma Serpentis, a star system
- Sigma Tama IV, a planet
- Sigma Trotti, a location
- Security terms
- Sigma 9 clearance, a top-level security clearance
- "Tuvok-Sigma-4", authorization code
- Other
A sigma in Mortimer Harren's theorem (left)
- Sigma (σ) was also a symbol meaning "sum". (VOY: "Good Shepherd")