"Augmentative and Alternative Communication" (AAC) can be defined as any device, system, or method that improves the ability of a child with a communication impairment to communicate effectively.  It can include sophisticated devices and systems (sign language, communication boards, or speech-generating devices) as well as less sophisticated means (facial expressions, non-speech vocalizations, gestures, etc.).  AAC is introduced when the student does not develop communication in the typical fashion, or experiences significant delays and is used to AUGMENT whatever communication the student possesses, as part of a multi-modal system. 

Examples of high tech AAC would be handheld tablets with appropriate apps--e.g., iPads with TD Snap, Proloquo2Go, TouchChat, etc OR dedicated speech generating devices like the product lines from Tobii-DynaVox, Prentke-Romich, or Saltillo