Languages of the Ottoman Empire
The language of the court and government of the Ottoman Empire was Ottoman Turkish, but many other languages were in contemporary use in parts of the empire. Although the minorities of the Ottoman Empire were free to use their language amongst themselves, if they needed to communicate with the government they had to use Ottoman Turkish.
Lingua franca
Lingua francas have developed around the world throughout human history, sometimes for commercial reasons (so-called "trade languages" facilitated trade) but also for cultural, religious, diplomatic and administrative convenience, and as a means of exchanging information between scientists and other scholars of different nationalities. The term is taken from the medieval Mediterranean Lingua Franca, a Romance-based pidgin language used by European merchants and sailors during the 2nd millennium. A world language – a language spoken internationally and learned and spoken by a large number of people – is a language that may function as a global lingua franca.