In finance, the coupon of a security is the payment made to the owner of the security for holding it. For example, the coupon of a government bond will be the annual interest payment that the government will send to the bondholder. Coupons do not merely have to be a fixed value. A coupon can be inflation-protected (there are inflation-protected Treasuries so while the interest rate remains the same, the principal of the bond is multiplied by the rate of inflation so the coupon rises as inflation rises), or linked to some other asset (e.g. a coupon that pays out an interest rate that is equal to the annual GDP growth rate).