These are followed by Madrid, Barcelona, Berlin, Rhine-Ruhr, Rome, and Milan, all with a metropolitan population of over 4 million. The EU also has numerous polycentric urbanised regions like Rhine-Ruhr (Cologne, Dortmund, Düsseldorf et al.), Randstad (Amsterdam, Rotterdam, The Hague, Utrecht et al.), Frankfurt Rhine-Main (Frankfurt), the Flemish Diamond (Antwerp, Brussels, Leuven, Ghent et al.) and Upper Silesian area (Katowice, Ostrava et al.). The European Union has 24 official languages: Bulgarian, Croatian, Czech, Danish, Dutch, English, Estonian, Finnish, French, German, Greek, Hungarian, Italian, Irish, Latvian, Lithuanian, Maltese, Polish, Portuguese, Romanian, Slovak, Slovene, Spanish, and Swedish. Important documents, such as legislation, are translated into every official language and the European Parliament provides translation for documents and plenary sessions. Due to the high number of official languages, most of the institutions use only a handful of working languages. The European Commission conducts its internal business in three "procedural languages": English, French, and German. Similarly, the Court of Justice of the European Union uses French as the working language, while the European Central Bank conducts its business primarily in English. Even though language policy is the responsibility of member states, EU institutions promote multilingualism among its citizens. English is the most widely spoken language in the EU, being understood by 51% of the EU population when counting both native and non-native speakers. German is the most widely spoken mother tongue (18% of the EU population), and the second most widely understood foreign language, followed by French (13% of the EU population). In addition, both are official languages of several EU member states. More than half (56%) of EU citizens are able to engage in a conversation in a language other than their mother tongue. A total of twenty official languages of the EU belong to the Indo-European language family, represented by the Balto-Slavic, the Italic, the Germanic, the Hellenic, and the Celtic branches. Only four languages, namely Hungarian, Finnish, Estonian (all three Uralic), and Maltese (Semitic), are not Indo-European languages. The three official alphabets of the European Union (Cyrillic, Latin, and modern Greek) all derive from the Archaic Greek scripts.