List of lingua francas
Turkish is still in use and widely spoken in several areas formerly part of the Ottoman Empire and may be understood by older people in other parts of the Middle East.
Croat Muslims
In 1585, a traveler and writer Marco A. Pigaffetta, in his "Itinerario" published in London, states: "In Constantinople it is customary to speak Croatian, a language which is understood by almost all official Turks, especially military men." Crucially though, the lingua franca at the time among Slavic elites in the Ottoman Empire was still Old Church Slavonic. For Italians traveling through to Istanbul, the language of the Slavic Croats was often the only exposure they had to any of the Slavic languages; indeed, Bulgarian and Macedonian dialects were far more common in Istanbul than Croatian.