# Difference between revisions of "Iff"

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

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

It is also known as a biconditional statement.

An iff statement $p\iff q$ means $p\implies q$ and $q\implies p$ at the same time.

## Examples

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

• if $p$ then $q$
• if $q$ then $p$

### Videos

Mathematical Logic ("I am in process of making a smoother version of this" -themathematicianisin).