"Sima" is a Greek letter, which is also pronounced as "Sima" and "Sima". The symbol is ∑, which means sum number in mathematics. It is a common symbol in mathematics and is mainly used to find the sum of multiple terms. Generally read as "variance equals a certain number".

∑ Description:

The small characters below ∑, such as i= 1, indicate that the sum starts from i= 1.

The little words above, such as n, mean add up to n.

For example, i= 1 is written below, N is written above, and Xi is written behind (I is the lower corner mark).

It means starting from x 1+x2+ ... +xn.

For example,1+2+3+4++100 = 5050 can be written as

For example, i=5 is written below, N is written above, and xi is written behind.

It means from x5+x6+…+xn.

Sigma (capital σ, lowercase σ) is the18th Greek letter. In Greek, if the last letter of a word is lowercase sigma, it should be written in lowercase sigma. In modern Greece, this number stands for 6.

Capital σ is used for: mathematical summation symbol. Lowercase σ is used for: a valence bond in chemistry, σ bond. Mechanical stress, statistical standard deviation, с of Cyrillic letter and S of Latin letter all evolved from Sigma.