Citizenship is membership in a political community (originally a city or town but now usually a country) and carries with it rights to political participation; a person having such membership is a citizen. It is largely coterminous with nationality, although it is possible to have a nationality without being a citizen (i.e., be legally subject to a state and entitled to its protection without having rights of political participation in it); it is also possible to have political rights without being a national of a state. In most nations, a non-citizen is a non-national and called either a foreigner or an alien. In the United States, because there is state citizenship, foreign is the legal term for someone not a citizen of the state, and alien is reserved for someone not a citizen of the United States. Thus New York insurance companies are foreign in New Jersey, while a Dutch insurer is alien. Citizenship is thus the political rights of an individual within a society. One can possess citizenship from one country and be a national of another country. Citizenship derives from a legal relationship with a state. Citizenship can be lost, as in denaturalisation, and gained, as in naturalisation. This book presents an outstanding line-up of contributors offering in-depth analyses of this important issue.