A, mathematical symbols:

"?" That is, "full-name quantitative symbol" is a mathematical symbol used to express full-name quantifiers. In Chinese, this symbol is pronounced "arbitrary".

For everyone.

Full name quantifier? X: P(x) means that P(x) is true for all X? n ∈ N: n2 ≥ n

For all; Do as you please; Yes, any one.

Second, "?" Input:

You can open the intelligent ABC input method, hold down the ALT key, enter 8704 and then release the ALT key to type.