Communication effectiveness: For people with augmentative systems, communication effectiveness almost always equates to comunication speed. Three factors work together to determine communication speed:
1. Selection speed – How fast can the user locate and press a key on a keyboard?
2. Number of selections required – Does an output require a multi-digit code or sequence?
3. Amount of  information retrieved – Is the output a single letter, single sound, a word, phrase a complete sentence?

Dedicated device: A physical AAC device made specifically as a communication device, not a generic computer with software.

Expressive language: What a person can output, what they can express, with words, gestures or symbols.

High tech system: An electronic communication device, either a computer with specialised software or a dedicated fit for purpose device.

Low tech system: Generally referred to as a pen and paper system. These are static systems that need to be physically manipulated such as graphic pointing boards or flip charts.

Receptive language: What a person can understand or receive with words, gestures or symbols.