This is a very interesting symbol in mathematics, which evolved from the English word Exist. Because the case of e is easy to be confused, so turning e upside down is the e in the mirror image. Existential quantifier means that some propositions A are B, which makes this proposition valid and is also used as a symbol in logic.
Introduction.
Special propositions use existential quantifiers, such as "some" and "few", and can also use "basically", "general" and "just some". Propositions containing existential quantifiers are also called existential propositions.
The phrases "you yi" and "at least one" are usually called existential quantifiers in logic, and are represented by the symbol "".
Propositions containing existential quantifiers are called special propositions (existential propositions).