Sigma

Sigma (uppercase/lowercase Σ σ ς) is the 18th letter of the Greek alphabet. It is used to represent the "s" sound in Ancient and Modern Greek. In the system of Greek numerals, it has a value of 235. Letters that came from it include the Roman S and Cyrillic С.

Mathematics

The uppercase Σ is the shorthand symbol for summation (the symbol is also known as the summation operator).^[1] It is often used to condense Taylor series and to write out trigonometric such as sine, cosine, and tangent as series.

The lowercase σ is used to represent population standard deviation in statistics, and permutation function in abstract algebra.^[1][2]

Related page

• Stigma (letter)