Several fictitious languages are mentioned in George R.R. Martin's fantasy series A Song of Ice and Fire. These include
the Common Tongue of Westeros, for which English is used in both the books and the television series
the Old Tongue of Westeros still spoken north of the Wall
the classical Valyrian (High Valyrian) of the Valyrian empire of Essos, and for a time of Westeros
nine Low Valyrian dialects of the Free Cities and the city-states of Slaver's Bay, which descend from High Valyrian and are on their way to becoming separate languages
Ghiscari, the extinct language of the empire of Ghis, which influenced the Low Valyrian dialects that replaced it in Slaver's Bay
Dothraki, the language of the steppe nomads of Essos
Lhazareen, the language of the Lhazar nomads
Qartheen, the language of the city of Qarth
the languages of Asshai and the Summer Isles
a trade pidgin of the port cities of Essos
Martin created only a few words for these languages, mostly proper names. For the television adaptation, Game of Thrones, two were elaborated by linguist David J. Peterson: Dothraki and High Valyrian. As of 2014, a Low Valyrian dialect, Astapori, was also created, though not as fully. All three are used with subtitles for dialogue in the series.
