∑ is a summation symbol, and its English name is Yima, and its Chinese name is Yima (capital σ, lowercase σ).

The eighteenth 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.

In mathematics, we use it as a summation symbol.

In physics, we use its lowercase letter σ to represent the area density. (Accordingly, ρ stands for bulk density and η stands for linear density).

Extended data

Sum rule: ∑ j =1+2+3+…+n.

Capital σ is used for mathematical summation symbols, such as ∑Pi, where i= 1, 2, ..., t, which is the sum of P 1+P2+ and ...+angle. Lowercase σ is used for statistical standard deviation.

Examples are as follows:

100/ upper limit n

∑ i = 1+2+3+4+5+ + 100

I= 1↘ lower bound I

Common symbols in mathematics:

(1) full-name quantifier.

(2)? Existential quantifier

(3) ├├decider (formula can be proved by L).

(4) Satisfier (the formula is valid on e and can be satisfied on e).

(5) the proposition of "not" operation, such as the negation of the proposition is ﹁ P.

(6) The "conjunction" ("sum") operation of ∧ proposition.

(7) "disjunction" ("or", "can be combined or") operation on the proposition ∨.

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