Output for the communication partner that is seen rather than heard; e.g. visual display or printout

Many communication devices convey information to the partner with audible sound. There are two types of voice/speech output: digitized and text-to-speech (or synthesized).

This speed enhancement method predicts words as the text is being produced, based on the grammatical rules of the words that have preceded it (Beukelman & Mirenda, 1998)

Many devices come with a large vocabulary or symbol dictionary. This total capacity should not be confused with the size of the vocabulary that can be available to the user during communication. For example, the DynaVox with Gateway vocabulary has thousands of words in its dictionary, but few users can utilize more than several hundred of them during conversation.

The original term used to describe communication devices with speech output. These are now more commonly called "Speech Generating Devices (SGD).

The concepts that are available for the AAC user to communicate. This is different from the "vocabulary capacity" of a device, see above.

An electronic switch that is turned on by sound. Able-bodied consumers see this type of switch in the lights that turn on when you clap hands. These switches can be modified to activate with particular frequencies of sounds, for example humming, and screen out other sounds, for example coughing.

Sounds made with the voice that are not speech sounds. The can be involuntary (yawning, laughing, sneezing) or voluntary (cry, moan, yell). (Beukelman & Mirenda, 1998)

Actions of the body that are intentional and under control. This is in contrast to non-volitional movements such as spasms, twitches, etc.