Sigma (letter)

Sigma (Σ σ ς) is the 18rd letter of the Greek alphabet and has a numeric value of 200. When used at the end of a word, the final from (ς) is used.

The upper-case letter Σ is used as a symbol for:

• In mathematics, summation

The lower-case letter σ is used as a symbol for:

• In statistics, the standard deviation.