\midThe \mid symbol is used to denote divisibility or conditional probability in mathematical expressions. It is a relation symbol that is often used in number theory and probability theory.
Indicates that 'a' divides 'b' without leaving a remainder.
a \mid bRepresents the probability of event A given that event B has occurred.
P(A \mid B)Used in modular arithmetic to show that x is congruent to y modulo n, and this relation divides z.
x \equiv y \pmod{n} \mid z