∑ English name: Sigma (capital∑, lowercase σ), which is the18th Greek letter.

Capitalized sigma is used for:

Sum symbols in mathematics and physics

For example:

∑Pi, where i= 1, 2, ..., t,

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

The lower limit of the sum is written below the sigma number, and the upper limit is written above the sigma number.