Tibetan

Tibetan was a language primarily used in Tibet. The Third Doctor displayed a basic knowledge of the language to the point where he could greet K'anpo Rimpoche. (DW: Planet of the Spiders) However, while in a pit on Chloris, the Fourth Doctor was unable to read Everest in Easy Stages as it was written in Tibetan and so he began reading Teach Yourself Tibetan. (DW: The Creature from the Pit)