The reward given to a debenture holder is called "interest." A debenture is a type of debt instrument issued by a company or government to raise funds. When an investor purchases a debenture, they are essentially loaning money to the issuer. The issuer then pays the investor interest on the loan at a predetermined rate and frequency until the debenture matures, at which point the principal is repaid to the investor. The interest paid to the debenture holder is typically fixed and is based on the amount of the loan, the interest rate, and the maturity of the debenture.