Shona is used to refer to a standardised language based on the central dialects of the Shona region. Shona languages form a dialect continuum from the Kalahari desert in the west to the Indian Ocean in the east and the Limpopo river in the south and the Zambezi in the north. While the languages are related, evolution and separation over the past 1000 years has meant that mutual intelligibility is not always possible without a period of acculturation. Therefore, Central Shona speakers have a difficult time understanding Kalanga speakers even though lexical sharing can be over 80% with some western Karanga dialects. In the same manner eastern dialects (Shanga) spoken by the Indian Ocean are also very divergent. There are many dialect differences in Shona, but a standardized dialect is recognized. According to information from Ethnologue (when excluding S16 Kalanga):