Definition of 'Mortgage' A debt instrument, secured by the collateral of specified real estate property, that the borrower is obliged to pay back with a predetermined set of payments. Mortgages are used by individuals and businesses to make large real estate purchases without paying the entire value of the purchase up front. Over a period of many years, the borrower repays the loan, plus interest, until he/she eventually owns the property free and clear. Mortgages are also known as "liens against property" or "claims on property." If the borrower stops paying the mortgage, the bank can foreclose.Investopedia explains 'Mortgage' In a residential mortgage, a home buyer pledges his or her house to the bank. The bank has a claim on the house should the home buyer default on paying the mortgage. In the case of a foreclosure, the bank may evict the home's tenants and sell the house, using the income from the sale to clear the mortgage debt. Mortgages come in many forms. With a fixed-rate mortgage, the borrower pays the same interest rate for the life of the loan. Her monthly principal and interest payment never change from the first mortgage payment to the last. Most fixed-rate mortgages have a 15- or 30-year term. If market interest rates rise, the borrowers payment does not change. If market interest rates drop significantly, the borrower may be able to secure that lower rate by refinancing the mortgage. A fixed-rate mortgage is also called a traditional" mortgage. With an adjustable-rate mortgage (ARM), the interest rate is fixed for an initial term, but then it fluctuates with market interest rates. The initial interest rate is often a below-market rate, which can make a mortgage seem more affordable than it really is. If interest rates increase later, the borrower may not be able to afford the higher monthly payments. Interest rates could also decrease, making an ARM less expensive. In either case, the monthly payments are unpredictable after the initial term. Other less common types of mortgages, such as interest-only mortgages and payment-option ARMs, are best used by sophisticated borrowers. Many homeowners got into financial trouble with these types of mortgages during the housing bubble years.