掉期
掉期合同是一种协议，规定了合同双方在一定时间段内交换一系列现金流的协议，交换发生在合同预置好的日期，通常只交换现金流净值（如Plain vanilla swap）。
Traditionally, the exchange of one security for another to change the maturity (bonds), quality of issues (stocks or bonds), or because investment objectives have changed. Recently, swaps have grown to include currency swaps and interest rate swaps.
If firms in separate countries have comparative advantages on interest rates, then a swap could benefit both firms. For example, one firm may have a lower fixed interest rate, while another has access to a lower floating interest rate. These firms could swap to take advantage of the lower rates.