Language

Countless different spoken, written, and gestural languages were used by different cultures throughout time and space. According to the Thirteenth Doctor, a minimum of 90,000,000,000 languages were spoken within the known universe of N-Space. (TV: Spyfall)

The Doctor had great expertise in linguistics, once claiming to be able to speak five billion languages. (TV: The Parting of the Ways) However, they still utilised the translation circuit of their TARDIS while travelling through space and time, though this was often more for the benefit of their companions. (TV: The End of the World, Cold War) Even while traveling on the fringes of the known universe, they kept the TARDIS systems open for new languages. (TV: Spyfall)

Language was constantly evolving. When Jo Grant invented the word "telempathy" to mean a sort of telepathic empathy, and asked the Third Doctor if this was a word, he responded that it was now. (AUDIO: The Tyrants of Logic)