The nation state is a certain form of state that has a territory where mainly one nation is located. The state is a political entity (the government, etc.); the nation is a cultural and/or ethnic entity. The term "nation state" means that the two are on the same territory, and this distinguishes the nation state from the other types of state, which existed before.
Clear examples of nation states include:
- Iceland: although the inhabitants are ethnically related to other Scandinavian groups, the national culture and language are found only in Iceland. There are no cross-border minorities— the nearest land is too far away.
- Japan: Japan is also traditionally seen as a good example of a nation-state, although Japan includes minorities of ethnically distinct Ryūkyū peoples, Koreans, Chinese, and on the northern island of Hokkaidō, the indigenous Ainu minority; see also Japanese Demographics .
- Portugal: although surrounded by other lands and people, the Portuguese nation has occupied the same territory for almost 900 years. A long time ago, Portugal was formed from groups of people that used to be separate. They all passed through and settled in the area that later became Portugal. They include: native Iberian peoples, Celts, ancient Mediterraneans (Greeks, Phoenicians, Romans), Germanic peoples like the Suebi and the Visigoths, invading Berbers and Arabs, and Jews.
What states existed before nation-states?
In Europe, in the eighteenth century, the classic non-national states were empires of many ethnicities, (the Austro-Hungarian Empire, the Russian Empire, the Ottoman Empire, the French Empire, the British Empire).
Characteristics of the nation-state
- They have a different attitude to their territory, compared to the dynastic monarchies. No nation would swap territory with other states simply, for example, because the king's daughter got married.
- They have a different type of border, mostly defined by where the cultural/ethnic (nation) group settles, but many nation states have also had borders based on geography like rivers and mountain ranges.
- The most noticeable characteristic is how much nation-states use the state as an instrument of national unity in economic, social and cultural life.
- But a unifying "national identity" can exist also in countries which have several ethnic or language groups. For example, Switzerland is constitutionally a confederation of cantons, and has four official languages, but it has also a 'Swiss' national identity, a national history, and a classic national hero, Wilhelm Tell.(see: Thomas Riklin, 2005. Worin unterscheidet sich die schweizerische "Nation" von der Französischen bzw. Deutschen "Nation"? 
- The creation of a new ethnicity from disparate elements is discussed at ethnogenesis.
- Hobsbawm, Eric J. (1992). Nations and Nationalism Since 1780: Programme, Myth, Reality. 2nd ed. Cambridge University Press. Template:Catalog lookup linkScript error: No such module "check isxn"..
- White, Philip L. (2006). "Globalization and the Mythology of the Nation State," In A.G.Hopkins, ed. Global History: Interactions Between the Universal and the Local Palgrave Macmillan, pp. 257–284. 
- From Paris to Cairo: Resistance of the Unacculturated (Identity and the Nation state)