Repayment of a loan through a fixed number of fixed-amount monthly installments. While the amount of the installment is same every month, however, it is apportioned unequally between interest and principal payments. In the early years, the major proportion (as much as 90 percent) of the installment amount goes towards payment of the interest. It is only in later years, when most of the interest has been paid off, that the principal balance begins to reduce significantly. Also called straight line amortization.