Supplemental Security Income (SSI): State funded and administered programs that provide supplementary income for individuals who are age 65 and older, blind or have another disability. (From AIRS NL-1000.2400-800) Social Security Disability Insurance (SSDI): A federal program that provides monthly cash benefits for disabled workers who are fully insured under the program, who are not capable of substantial gainful work and who have completed a five month waiting period. (AIRS NS-1800.8000)