This section aims to provide learners with an understanding of Autism Spectrum Disorder (ASD), including its common characteristics and areas of impairment. It covers the definition of ASD as a neurodevelopmental disorder characterized by differences in social communication and social interaction, as well as restricted and repetitive patterns of behavior, interests, or activities. Learners will discuss early “red flags” associated with autism, identify potential risk factors, and become familiar with terminology commonly used in ASD assessment and diagnosis, including pragmatic language, receptive and expressive language, sensory-motor skills, social skills, joint attention, and stereotypy. The section also introduces conditions commonly considered in the differential diagnosis of ASD, such as learning disabilities and processing disorders, and explores common comorbid disorders and conditions associated with ASD.