Social Security Disability Insurance (SSDI) is a federal social insurance program that provides monthly cash benefits to nonelderly disabled workers and their eligible dependents, provided the worker paid into the system for a sufficient number of years. The program is part of Old-Age, Survivors, and Disability Insurance (OASDI), commonly known as Social Security. As with Old-Age and Survivors Insurance (OASI)-the retirement component of Social Security-benefits are based on a worker's past earnings in covered employment. The Social Security Administration (SSA) administers both SSDI and OASI.