For example, the full-name proposition "p(x) holds for any x in m" can be abbreviated as? X∈M, p(x), pronounced as "P (x) holds for any x belonging to m."

Definition: The phrases "some", "at least one", "one" and "existence" all mean individuals or parts. Such words are called existential quantifiers. Use the symbol "?" (the reverse "e") means

Propositions containing existential quantifiers are called special propositions.

Special proposition "There is an X in M, which makes p(x) hold". Jane wrote:? x ∈ M，p(x)

Read: there is an x that belongs to m, which makes p(x) hold.