Citizenship of the United States
A person who is considered a citizen by more than one nation has "dual citizenship". It is possible for a United States citizen to have dual citizenship; this can be achieved in various ways, such as by birth in the United States to a parent who is a citizen of a foreign country (or in certain circumstances the foreign nationality may be transmitted even by a grandparent) by birth in another country to a parent(s) who is/are a United States citizen/s, or by having parents who are citizens of different countries. Anyone who becomes a naturalized U.S. citizen is required to renounce any prior "allegiance" to other countries during the naturalization ceremony; however, this renunciation of allegiance renunciation of citizenship to those countries.
Citizenship of the United States
U.S. citizens can relinquish their citizenship, which involves abandoning the right to reside in the United States and all the other rights and responsibilities of citizenship. "Relinquishment" is the legal term covering all seven different potentially-expatriating acts (ways of giving up citizenship) under . "Renunciation" refers to two of those acts: swearing an oath of renunciation before a U.S. diplomatic or consular officer abroad, or before an official designated by the Attorney General within the United States during a state of war. Out of an estimated three to six million U.S. citizens residing abroad, between five and six thousand relinquished citizenship each year in 2015 and 2016. U.S. nationality law treats people who performs potentially-expatriating acts with intent to give up U.S. citizenship as ceasing to be U.S. citizens from the moment of the act, but U.S. tax law since 2004 treats such individuals as though they remain U.S. citizens until they notify the State Department and apply for a Certificate of Loss of Nationality (CLN).