In sequent calculus formulations of proof theory, the two sets, multisets, or sequences of formulae (possibly empty) appearing to the left and right of ⇒. As multisets, a cedent may contain multiple instances of a formula $\phi$. In most presentations of sequent calculi, cedents are treated as sequences, that is, a cedent $\Delta$ and a permutation of $\Delta$ are treated as distinct, although when a sequent calculus includes the structural rule of exchange, this ordering is superfluous.