The average amount of time that will elapse from the date of a security's issuance until each dollar of principal is repaid to the investor. The weighted-average life of each class of a REMIC is only an assumption. The average amount of time that each dollar of principal is actually outstanding is influenced by, among other factors, the rate at which principal, both scheduled and unscheduled, is paid on the mortgage loans underlying the MBS that back the REMIC.