Wittmann (1991) posits that the Sri Lankan languages, as a group, are a language isolate ('prototype' sign language), though one developed through stimulus diffusion from an existing sign language. It is not known if they are related to each other, nor how many there are.
^a Sign-language names reflect the region of origin. Natural sign languages are not related to the spoken language used in the same region. For example, French Sign Language originated in France, but is not related to French. ^b Denotes the number (if known) of languages within the family. No further information is given on these languages.