According to the Individuals with Disabilities Education Act’s (IDEA), multiple disabilities refers to “concomitant [simultaneous] impairments (such as intellectual disability-blindness, intellectual disability-orthopedic impairment, etc.), the combination of which causes such severe educational needs that they cannot be accommodated in a special education program solely for one of the impairments. The term does not include deaf-blindness.”
In other words, a student whose special needs are categorized under multiple disabilities requires coinciding adaptions for more than one disability. The exception is the combination deafness and blindness, as this pair of impairments has its own classification under IDEA.