Biconditional (Personal website)

Biconditional

\[\begin{equation*}
  P \iff Q \qor P \equiv Q,
\end{equation*}
\]

and read

	“\(P\) if and only if \(Q\)”
or	“\(P\) is equivalent to \(Q\)”,

that is ‘true’ if and only if

\(P\) and \(Q\) are both either ‘true’ or ‘false’,

which is equivalent to

\[\begin{equation*}
  (P \implies Q) \> \land \> (Q \implies P).
\end{equation*}
\]