Slovakia (/slɵˈvaːkiə/; Slovak: Slovensko [ˈsloʋensko]), officially the Slovak Republic (Slovak: Slovenská republika, listen ), is a country in Central Europe. It is bordered by the Czech Republic and Austria to the west, Poland to the north, Ukraine to the east and Hungary to the south. Slovakia's territory spans about 49,000 square kilometres (19,000 sq mi) and is mostly mountainous. The population is over 5 million and comprises mostly ethnic Slovaks. The capital and largest city is Bratislava. The official language is Slovak, a member of the Slavic language family.The Slavs arrived in the territory of present-day Slovakia in the 5th and 6th centuries. In the 7th century, they played a significant role in the creation of Samo's Empire and in the 9th century established the Principality of Nitra. In the 10th century, the territory was integrated into the Kingdom of Hungary, which itself became part of the Habsburg Empire and the Austro-Hungarian Empire. After World War I and the dissolution of the Austro-Hungarian Empire, the Slovaks and Czechs established Czechoslovakia. A separate Slovak Republic (1939–1945) existed in World War II as a client state of Nazi Germany. In 1945, Czechoslovakia was reestablished under communist rule as a Soviet satellite. Slovakia became an independent state on 1 January 1993 after the peaceful dissolution of Czechoslovakia.Slovakia is a high-income advanced economy. The country joined the European Union in 2004 and the Eurozone on 1 January 2009. Slovakia is also a member of the Schengen Area, NATO, the United Nations, the OECD and the WTO.