A dual citizen is someone who is a legal citizen of two countries. It is also possible for someone to hold multiple citizenship, meaning that he or she is a citizen of three or more countries, although this is relatively rare. There are both advantages and disadvantages to dual citizenship, as one might imagine.
In some cases, someone becomes a dual citizen without having much choice in the matter. For example, someone born in Canada to parents with United States citizenship will become a dual citizen, because the United States offers citizenship to people via jus sanguinis, the “right of the blood,” and Canada offers citizenship on the basis of jus solis, the “right of the soil.” Dual citizenship entitles someone to all the rights of citizenship in both countries, but it also carries responsibilities.
For example, in some cases, a dual citizen may be required to pay taxes in both nations. Dual citizens also owe their allegiance to both of the countries to which they belong, and they may need to fulfill obligations such as military service. In the event that war breaks out between both nations, a dual citizen may be in an awkward position; in that situation, a dual citizen is commonly expected to renounce citizenship in one of the nations.
It is also possible to become a dual citizen through naturalization. For instance, a Canadian citizen could move to Germany and undergo Germany's naturalization process. At the end of the process, he or she would become a dual citizen. In nations which do not recognize dual citizenship, naturalized citizens will be asked to renounce citizenship in their nations of origin before they will be admitted as full citizens. Citizens of a country which does not recognize dual citizenship should be aware that through naturalization in another country, they will forfeit citizenship in their nation of origin.
Several countries, including the United States, frown upon dual citizenship, but they do recognize it, and agents of the United States government cannot compel foreign nationals into giving up their dual citizenship, contrary to popular belief. Other nations acknowledge that it is possible to be a dual citizen, but they treat dual citizens as their citizens exclusively. This means that someone who holds dual citizenship may not be protected by one government when under the jurisdiction of another; for example, the Canadian-German citizen above could not appeal to the Canadian embassy for help while in Germany.