A person may have multiple citizenships. A person who does not have citizenship of any state is said to be stateless, while one who lives on state borders whose territorial status is uncertain is a border-lander.
Each country has its own policies, regulations and criteria as to who is entitled to its citizenship. A person can be recognized or granted citizenship on a number of bases. Usually citizenship based on circumstances of birth is automatic, but in other cases an application may be required.
Citizenship by birth (jus sanguinis). If one or both of a person's parents are citizens of a given state, then the person may have the right to be a citizen of that state as well.[a] Formerly this might only have applied through the paternal line, but sex equality became common since the late twentieth century. Citizenship is granted based on ancestry or ethnicity and is related to the concept of a nation state common in Europe. Where jus sanguinis holds, a person born outside a country, one or both of whose parents are citizens of the country, is also a citizen. Some states (United Kingdom, Canada) limit the right to citizenship by descent to a certain number of generations born outside the state; others (Germany, Ireland) grant citizenship only if each new generation is registered with the relevant foreign mission within a specified deadline; while others (France, Switzerland, Italy) have no limitation on the number of generations born abroad who can claim citizenship of their ancestors' country. This form of citizenship is common in civil law countries.
Born within a country (jus soli). Some people are automatically citizens of the state in which they are born. This form of citizenship originated in England, where those who were born within the realm were subjects of the monarch (a concept pre-dating citizenship) and is common in common law countries. Most countries in the Americas grant unconditional jus soli citizenship, while it has been limited or abolished in almost all other countries.
In many cases, both jus soli and jus sanguinis hold citizenship either by place or parentage (or both).
Citizenship by marriage (jus matrimonii). Many countries fast-track naturalization based on the marriage of a person to a citizen. Countries which are destinations for such immigration often have regulations to try to detect sham marriages, where a citizen marries a non-citizen typically for payment, without them having the intention of living together. Many countries (United Kingdom, Germany, United States, Canada) allow citizenship by marriage only if the foreign spouse is a permanent resident of the country in which citizenship is sought; others (Switzerland, Luxembourg) allow foreign spouses of expatriate citizens to obtain citizenship after a certain period of marriage, and sometimes also subject to language skills and proof of cultural integration (e.g. regular visits to the spouse's country of citizenship).
Naturalization. States normally grant citizenship to people who have entered the country legally and been granted permit to stay, or been granted political asylum, and also lived there for a specified period. In some countries, naturalization is subject to conditions which may include passing a test demonstrating reasonable knowledge of the language or way of life of the host country, good conduct (no serious criminal record) and moral character (such as drunkenness, or gambling), vowing allegiance to their new state or its ruler and renouncing their prior citizenship. Some states allow dual citizenship and do not require naturalized citizens to formally renounce any other citizenship.
Citizenship by investment or Economic Citizenship. Wealthy people invest money in property or businesses, buy government bonds or simply donate cash directly, in exchange for citizenship and a passport. Whilst legitimate and usually limited in quota, the schemes are controversial. Costs for citizenship by investment range from as little as $100,000 (£74,900) to as much as €2.5m (£2.19m)
Excluded categories. In the past there have been exclusions on entitlement to citizenship on grounds such as skin color, ethnicity, sex, and free status (not being a slave). Most of these exclusions no longer apply in most places. Modern examples include some Arab countries which rarely grant citizenship to non-Muslims, e.g. Qatar is known for granting citizenship to foreign athletes, but they all have to profess the Islamic faith in order to receive citizenship. The United States grants citizenship to those born as a result of reproductive technologies, and internationally adopted children born after February 27, 1983. Some exclusions still persist for internationally adopted children born before February 27, 1983 even though their parents meet citizenship criteria.