Russian (language)
Russian was a language which orginated in Russia. When the Eleventh Doctor and Clara Oswald arrived on a Soviet submarine, the TARDIS's translation circuit routinely translated the language, which caused confusion when Clara, who along with the Doctor was speaking Russian from the crew's perspective, said that she couldn't speak Russian. (TV: Cold War)
The word "polyot" meant "flight" in Russian, hence the name of the Polyot-one rocket-ship. (PROSE: The Shoreditch Incident)
When the Twelfth Doctor, O'Donnell and Bennett visited a military training base in 1980, a location that would later home their underwater base, they found that the base consisted of a fake Russian town named Краснодар, with accompanying Russian signs. The purpose of the town was to train soldiers during a time of cold war. (TV: Before the Flood)
Russian was one of the languages spoken in Uzbekistan (AUDIO: Brave New Town)
The interface of Soyuz spacecraft used both Russian and English languages. (TV: Praxeus)
In one possible timeline, in which Earth became Orphan 55, the Doctor found a plate that said "Novosibirsk". According to Graham O'Brien, the word looked like Russian. (TV: Orphan 55)
