Arbitrage is generally defined as capitalising on a discrepancy in quoted prices, triggered by the violation of an equilibrium (pricing) condition. It is often the case that arbitrage is portrayed to be a riskless operation, in the sense that all of the decision variables are known when the decision is made, but the process invariably involves risk, such as the risk of non-delivery (Herstatt risk). The arbitrage process restores equilibrium via changes in the supply of and demand for the underlying commodity, asset or currency. These changes in supply and demand cause price changes in such a way as to restore the equilibrium no-arbitrage condition. At this point the arbitrage process comes to an end, as the operation becomes unprofitable.