# Iff

Iff is an abbreviation for the phrase "if and only if."

In mathematical notation, "iff" is expressed as $\iff$.

If a statement is an "iff" statement, then it is a biconditional statement.

## Example

In order to prove a statement of the form, "$p$ iff $q$," it is necessary to prove two distinct implications:

• $p$ implies $q$ ("if $p$, then $q$")
• $q$ implies $p$ ("if $q$, then $p$")