Wikipedia:Citizenship and nationality

Citizenship and nationality are two options in the Infobox person template which, though often related, are distinct concepts with different meanings. The purpose of this guideline is to provide editors with clear instructions that explain the differences between nationality and citizenship, why they are sometimes mistakenly used as synonyms, and how to decide whether either is appropriate for use in a given circumstance.

Definitions
Citizenship is a legal status in a political institution such as a city or a state. The relationship between a citizen and the institution that confers this status is formal, and in contemporary liberal-democratic models includes both a set of rights that the citizen possesses by virtue of this relationship, and a set of obligations or  duties that they owe to that institution and their fellow citizens in return.

Nationality, on the other hand, denotes where an individual has been born, or holds citizenship with a state. Nationality is obtained through inheritance from his/her parents, which is called a natural phenomenon. On the other hand, an individual becomes a naturalized citizen of a state only when they are accepted into that's nations framework, and then legally their nationality has changed by international law. Article 15 under Universal Declaration of Human Rights states "Everyone has the right to a nationality". "No one shall be arbitrarily deprived of his nationality nor denied the right to change his nationality".

Essentially, an individual is able to change their nationality through nationalization, citizenship by descent or inheritance of nationality from parents. An example of nationality is Italian to a person with Italian roots born in the United States.

Relationship
While the terms "citizenship" and "nationality" are sometimes used interchangeably, this is for political purposes rather than because there is no difference between the two. The most familiar instance of this is the use of "nationality" to denote state citizenship (as in nationality law). This is common practice for many states, under the assumption that because they are supposed to be "nation-states" (meaning that the boundaries of the nation and the state coincide), making a distinction is unnecessary – all citizens are also nationals.

In reality, the majority of contemporary states are multi-national, and fewer than ten per cent can be accurately described as nation-states. Many, however, still characterise themselves this way because of the political legitimacy that nation-statehood is thought to provide. The reasons for this are complex, but can be summarised as the result of the increased importance of norms of democratic governance and national self-determination in both domestic and "international" politics since at least the Treaty of Versailles that ended the First World War.

Examples
An obvious example of when citizenship and nationality will differ is naturalization through immigration. In this circumstance a person may be required to renounce their previous citizenship(s) (depending on the laws of both the original and receiving states), but this does not imply that they have renounced their previous nationalities as well. For example, an immigrant from Germany to the United States of America may apply for and receive American citizenship, but it is unlikely that she or anyone else would then say that she was no longer "German" in any sense, despite the fact that in most circumstances Germany until recently used to require its emigrants to renounce their German citizenship before adopting another. This is why Bruce Willis, a German-American, is considered simply as "American".

Multinational states provide another example. While many citizens of Canada and the United Kingdom, for instance, see Canada or the United Kingdom as their respective nations, a significant proportion of them do not (or, at least, this is not their only national identity). Despite their citizenship, many Québécois, Aboriginal peoples, Acadians, English, Scots, Welsh, Irish and Northern Irish see those groups as their nations, even if they may also identify with the state or the nation associated with it.

Use
As a legal status, citizenship is easier to determine than nationality in most circumstances and should be given priority when using the Infobox person template. Nationality should be listed only in addition to citizenship, and only in cases where it is verifiable and relevant to the article. For most articles, this just means using the  field instead of the   field, as the citizenship of the article's subject is what editors are usually trying to convey with the latter term.