albanian language altaic languages americas ancient greek australia balkan sprachbund bulgarian language caucasus chinese language classical latin dialect dialect continuum dravidian languages east asian languages ethiopia ethiopian language area future tense german language greek language india as a linguistic area indo-aryan languages indo-european languages infinitive language language contact language convergence language merger macedonian language mesoamerican linguistic area mongolian language mutual intelligibility new guinea pueblo linguistic area romani language romanian language serbo-croatian language sino-tibetan south slavic languages sprachraum thai language turkic languages uralic languages vietnamese language vowel harmony