This document defines key terms related to disabilities and behavior, including disability, behavior, assessment, and intervention. It then provides descriptions of the 13 categories of disabilities recognized by the Individuals with Disabilities Education Act (IDEA), including brief definitions and common examples for many categories. The categories discussed are learning disabilities, speech or language impairments, other health impairments, intellectual disabilities, emotional disturbance, autism, multiple disabilities, developmental delay, hearing impairment/deafness, orthopedic impairments, visual impairments, traumatic brain injury, and deaf-blindness.