Disability definition under section 80U clarifies covered conditions and the recognised medical authorities for certification. For income-tax purposes disability adopts meanings from the Persons with Disabilities Act and includes autism, cerebral palsy and multiple disabilities from the National Trust Act; a medical authority-the authority under the Persons with Disabilities Act or any authority notified by the Central Government-must certify these conditions and the categories person with disability and person with severe disability, the latter encompassing individuals with the severe-disability standard specified in the relevant Acts.