Chakavian
Chakavian in its actual use is the least spoken Serbo-Croatian dialect, being spoken only by 12% Croats. It is now mostly reduced in southwestern Croatia along the eastern Adriatic: Adriatic islands, and sporadically in the mainland coast, with rare inland enclaves up to central Croatia, and minor enclaves in Austria and Montenegro. All areas of old contacts with Romance languages.
List of lingua francas
Serbo-Croatian is a lingua franca in several of the territories of the former Yugoslavia, that is, modern Bosnia and Herzegovina, Croatia, Montenegro and Serbia. In those four countries it is the main native language, and is also spoken by ethnic minorities. For example, a Hungarian from Vojvodina and an Italian from Istria might use it as a shared second language. Most people in Slovenia and Macedonia can understand or speak Serbo-Croatian as well. It is a pluricentric language and is commonly referred to as Bosnian, Croatian, Serbian or Montenegrin depending on the background of the speaker.