Slovakia or (officially the Slovak Republic; Slovak: Slovensko (), long form Slovenská republika ()) is a sovereign state in Central Europe. It has a population of over five million and an area of about . Slovakia is bordered by the Czech Republic and Austria to the west, Poland to the north, Ukraine to the east and Hungary to the south. The largest city is the capital, Bratislava, and the second largest is Košice. Slovakia is a member state of the European Union, Eurozone, Schengen Area, NATO, the United Nations, the OECD and the WTO, among others. The official language is Slovak, a member of the Slavic language family. The Slavs—ancestors of the Slovaks—arrived in the territory of present-day Slovakia in the 5th and 6th centuries during the migration period. In the 7th century, Slavs inhabiting this territory played a significant role in the creation of Samo’s Empire, historically the first Slavic state which had its center in Western Slovakia. During the 9th century, Slavic ancestors of the Slovaks established another political entity, the Principality of Nitra, which later together with the Principality of Moravia, formed Great Moravia. After the 10th century the territory of today’s Slovakia was gradually integrated into the Kingdom of Hungary, which itself became part of the Austro-Hungarian Empire or Habsburg Empire. After WWI and the dissolution of the Austro-Hungarian Empire, the nation of Slovaks and Czechs established their mutual state – Czechoslovakia. A separate Slovak state existed during World War II and was a client state of Nazi Germany (from 1939 to 1944). In 1945 Czechoslovakia was reestablished. The present-day Slovakia became an independent state on 1 January 1993 after the peaceful dissolution of Czechoslovakia. Slovakia is a high-income advanced economy with one of the fastest growth rates in the European Union and the OECD. The country joined the European Union in 2004 and the Eurozone on 1 January 2009.