This situation, the use of Literary Chinese throughout the Chinese cultural sphere despite the existence of disparate regional vernaculars, is called diglossia. It can be compared to the position of Classical Arabic relative to the various regional vernaculars in Arab lands, or of Latin in medieval Europe. The Romance languages continued to evolve, influencing Latin texts of the same period, so that by the Middle Ages, Medieval Latin included many usages that would have been foreign to the Romans. The coexistence of Classical Chinese and the native languages of Japan, Korea and Vietnam can be compared to the use of Classical Latin in nations that natively speak non-Latin-derived Germanic languages or Slavic languages, to the position of Arabic in Persia, or the position of the Indic language Sanskrit in South India and Southeast Asia. However, the non-phonetic Chinese writing system causes a unique situation where the modern pronunciation of the classical language is far more divergent (and heterogeneous, depending on the native – not necessarily Chinese – tongue of the reader) than in analogous cases, complicating understanding and study of Classical Chinese further compared to other classical languages.