(n.) The Greek letter /, / or / (English S or s). It originally had the form of the English C.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). sigma. Retrieved September 21, 2026, from http://smartdefine.org/sigma/definitions/2061940 |
| Chicago | Webster's. 2011. "sigma" http://smartdefine.org/sigma/definitions/2061940 (accessed September 21, 2026). |
| Harvard | Webster's 2011, sigma, Smart Define, viewed 21 September, 2026, <http://smartdefine.org/sigma/definitions/2061940>. |
| MLA | Webster's. "sigma" 28 May 2011. Web. 21 September 2026. <http://smartdefine.org/sigma/definitions/2061940> |