Sigma (noun)

1. The 18th letter of the Greek alphabet (Σ, σ), transliterated as "s".
2. Used to represent standard deviation in statistics.

Origin:

Late 16th century: from greek sigma, the name of the letter σ.

Examples:

1. Sigma is the symbol for the sum in mathematics.
2. Sigma is the symbol for the standard deviation in statistics.
3. Sigma is used in Greek letter notation for various fields of study.
4. Sigma is the 18th letter of the Greek alphabet.
5. The Greek letter sigma is often used to represent the sum of a series.