Ireland, also known as the Republic of Ireland (Poblacht na hÉireann), is a country in Europe occupying about five-sixths of the island of Ireland. The capital is Dublin, located in the eastern part of the island. The state shares its only land border with Northern Ireland, one of the constituent countries of the United Kingdom. It is otherwise surrounded by the Atlantic Ocean, with the Celtic Sea to the south, Saint George's Channel to the south east, and the Irish Sea to the east. It is a unitary, parliamentary republic elected president serves as head of state. The head of government, the Taoiseach, is nominated by the lower house of parliament, Dáil Éireann.