Nationalism is an idea and movement that holds that the nation should be congruent with the state. As a movement, nationalism tends to promote the interests of a particular nation, especially with the aim of gaining and maintaining the nation's sovereignty (self-governance) over its homeland to create a nation state. Nationalism holds that each nation should govern itself, free from outside interference (self-determination), that a nation is a natural and ideal basis for a polity and that the nation is the only rightful source of political power. It further aims to build and maintain a single national identity, based on shared social characteristics of culture, ethnicity, geographic location, language, politics, religion, traditions and belief in a shared singular history, and to promote national unity or solidarity. Nationalism, therefore, seeks to preserve and foster a nation's traditional culture. There are various definitions of a "nation", which leads to different types of nationalism. The two main divergent forms are ethnic nationalism and civic nationalism.