A financial derivative in which each counterparty agrees to the exchange of a fixed /floating rate cash flow on a certain notional amount. This rate is typically multiplied by an accrual factor calculated with a day count fraction. In case both legs have the same currency, the notional amount is not exchanged; instead, it is used to define the cash flow to be exchanged. When the legs have different currencies, the notional amount is exchanged at the start and end of the swap term.