In the context of human–computer interaction, a modality is the classification of a single independent channel of input/output between a computer and a human.
Multiple modalities can be used in combination to provide complementary methods that may be redundant but convey information more effectively.
Though not commonly implemented as computer-human modality, tactition can achieve an average of 125 wpm[6] through the use of a refreshable Braille display.
Common input devices are often interchangeable if they have a standardized method of communication with the computer and afford practical adjustments to the user.
Certain modalities can provide a richer interaction depending on the context, and having options for implementation allows for more robust systems.