A binary logical connective, denoted

\begin{equation*} P \oplus Q, \end{equation*}

that is true if and only if

exactly one of \(P\) and \(Q\) is true,

which is equivalent to

\begin{equation*} (P \land \lnot Q) \lor (\lnot P \land Q) \end{equation*}

being a tautology.

[1, Sec. 0.2], [2, Sec. 5.1]