Most present-day societies are multilingual, though multilingualism is not always recognised by public institutions. Nation states often include regional minorities that have their own language; quite often, populations in border areas speak the language of the neighbouring country. In ex-colonial states, a former colonial language often continues to serve as the official state language while most people use tribal or ethnic languages for everyday informal communication. Most urban centres around the world have attracted large-scale immigration from across the country or from overseas, giving rise to urban linguistic minorities. Some countries have two or more national languages, while others recognise regional or minority languages and grant them limited official status. In most multilingual communities, the languages tend to have distinct specialised functions. Quite often, one language is used for informal communication within the group, another for inter-ethnic communication, and sometimes yet another language is used in the public domain - for education and media and in correspondence and institutions. Multilingual societies face the problem of maintaining an effective medium of communication while safeguarding the linguistic and cultural heritage of the various population sectors.