The ∑ symbol means sum, and the ∑ pronunciation is sigma, which means sum and sum in English.

1, superscript: n represents the upper bound, which refers to the elements in a poset that are greater than or equal to all the elements in its subset.

2. Subscript: I stands for the lower limit. If a set of real numbers M has a real number S, so that any number in M is greater than S, then S is called a lower bound of M. ..

Scientific field:

Greek letters are used in mathematics, science and engineering. In mathematics, Greek letters are usually used to represent constants, special functions and some specific variables. In the field of mathematics, the meanings of uppercase and lowercase Greek letters are usually different and irrelevant.