Autism Spectrum Disorder (ASD) or syndrome is an increasingly popular term that refers to a broad definition of autism. This includes the classical form of the disorder, as well as closely related disabilities that share many of the core characteristics of autism but may not be as severe or extensive.

Autism is a brain development disorder that usually manifests during infancy or childhood. It is distinguished not by a single symptom, but by a multitude of symptoms. It can be characterised by impaired social interaction and communication, and by restricted and repetitive behaviour.