Approval that the Health Care Financing Administration (HCFA, the federal agency that administers the Medicaid program) may grant to state Medicaid programs to exempt them from specific aspects of Title XIX, the federal Medicaid law. Most federal waivers involve loss of freedom of choice regarding which providers beneficiaries may use, exemption from requirements that all Medicaid programs be operated throughout an entire state, or exemption from requirements that any benefit must be available to all classes of beneficiaries (which enables states to experiment with programs only available to special populations).