Ukraine (Ukrainian: Україна) is a country in Eastern Europe. It lies at the northwest end of the Black Sea, with Russia to the east, Belarus to the north, Poland to the northwest, Slovakia and Hungary to the west, and Romania to the south west and south, with Moldova in between. Most of the country (the central and eastern portions) was formerly a part of Russian Empire; after the October Revolution and the Civil War, the entire country, known as the Ukrainian Soviet Socialist Republic, was a part of the Soviet Union. Ukraine is the second-largest country in Europe, albeit with a slightly declining population.