Poland, officially the Republic of Poland, is a country located in Central Europe. It is bordered by Germany to the west, the Czech Republic and Slovakia to the south, Ukraine and Belarus to the east, and the Baltic Sea, Lithuania, and Russia to the north. Poland shares a maritime border with Denmark and Sweden in the Baltic Sea. Since May 1, 2004, the republic has been a member state of the European Union. Officially the country is known as Republic of Poland, in Polish Rzeczpospolita Polska. The word Rzeczpospolita is the historic name that has been used continuously since the 16th century during the Polish-Lithuanian Commonwealth, which was an elective monarchy. The term Rzeczpospolita can mean "commonwealth" or also "republic". During communist rule from 1952 to 1989 the country's official name was the People's Republic of Poland (Polska Rzeczpospolita Ludowa), which was the only break in the official historical designation.