"Bonds are financial assets issued by governments, central banks or companies. Their holders receive some fixed payments at future dates. The life time of a bond is specified by its maturity - the date when the nominal value of the bond is paid. All previous payments are called coupons and they are usually fixed as fractions of the nominal value of the bond. The payments received by the holder, although fixed, can, however, be influenced by the credit rating of the issuer. This means that in case of the issuer's bankruptcy the promised payments can be reduced or even canceled"--