∑ English name: Sigma (capital∑, lowercase σ), which is the18th Greek letter. In Greek, if the last letter of a word is lowercase sigma, what should it be written as? This letter is also called final sigma(Unicode: U+03C2). In modern Greece, this number stands for 6.

Capitalized sigma is used for:

Mathematical summation symbol

For example:

∑Pi, where i= 1, 2, ..., t,

Is to find the sum of P 1+P2+ and ...+angle.

Lowercase σ is used for: statistical standard deviation.

Both the с of Cyrillic alphabet and the S of Latin alphabet are derived from Sigma.

The code name of Sigma, the villain in the series Rockman X, also refers to peace.

This writing means ∑ j =1+2+3+...+n.