Some have even become prominent languages within a country, such as Tok Pisin in Papua New Guinea and Bislama in Vanuatu. Other bridges promoting communication are lingua francas. A lingua franca is a common language used by groups whose mother tongues are different. In the Central African Republic, for instance, speakers of various local languages can communicate by means of Sango. Among diplomats, English and French are languages used as lingua francas.
Pidgins are lingua francas, and creoles can be also.
In different regions inside a country, local varieties of the national language may be used, which are called dialects. The more isolated the region, the more marked the differences may be. In time, some dialects become so different from the original language of the area that they become another language. In some cases it is not easy for linguists to distinguish between a language and a dialect. Also, since languages change constantly, dialects sometimes die out from disuse, and with them dies a piece of history.