Naturalization in the United States is the process by which a foreign citizen acquires U.S. citizenship by meeting certain requirements set by U.S. law. The naturalization process has a “standard” format, but varies significantly depending on the personal status of the applicant, such as whether he or she is married to a U.S. citizen or has served in the U.S. military.

The formal naturalization process requires the applicant to have lived legally in the US for at least five years as a permanent resident (with a green card). In addition, he or she must demonstrate good moral and fiscal conduct, proficiency in English, and a basic knowledge of American history and government. The applicant must also be interviewed and tested, unless the applicant has a disability that waives this requirement. The process concludes with the oath of allegiance to the United States and the official acquisition of U.S. citizenship.

However, there are differences in naturalisation for certain categories of applicants. For aliens married to a US citizen, the process is more favorable and usually faster. Spouses of U.S. citizens can apply for naturalization after three years of legal residence in the U.S., instead of five years for other applicants. They are also required to prove that they maintain a continuing and permanent relationship with the U.S. spouse, that they are of good moral and tax standing, and that they have lived together for at least three years.

Similarly, for people who have served at least one year in total in the US military, naturalization can be done more quickly and with fewer requirements. Active duty soldiers do not need to meet the usual requirements for permanent residency or time in the United States. They can apply for naturalization even during their service and the process is processed on a priority basis. Also, soldiers are not required to pass formal interviews and tests of knowledge of American history and government, although they must prove that their service was legal and good. This process is intended to recognize their service and strengthen the U.S. relationship with members of the armed forces.

Despite favorable procedures for spouses of U.S. citizens and soldiers, it is important to note that these procedures apply only to certain categories of aliens and may vary depending on the law and the specific circumstances of each applicant. For example, military personnel may be subject to enhanced security checks due to the nature of their service, while spouses of U.S. citizens may need to provide additional documentation to prove the validity of their marriage.

Overall, naturalisation in the US is a process that can vary considerably depending on the personal situation of the applicant. Whether the applicant is the spouse of a US citizen or a soldier, special naturalization procedures offer significant advantages and conveniences over the standard process for other foreigners.

The most important advantage of naturalisation, i.e. US citizenship, over the green card is that US citizens generally cannot be deported from the US, even if they commit crimes. Also, US citizens can stay outside the US indefinitely without risk of losing their US citizenship.

Some countries such as China, Japan and India do not allow dual citizenship, so any acquisition of US citizenship implies an automatic loss of the previous citizenship. Greece, Britain, France, France, Canada and most other countries do not impose such restrictions – so a Greek citizen can become a naturalized American citizen and retain Greek citizenship.