Naturalization (or naturalisation) is the legal act or process by which a non-national of a country acquires after birth the nationality of that country. The definition of the International Organization for Migration of the United Nations does not include automatic acquisition that is not initiated by the individual concerned or his or her legal agent or acquisition of nationality by declaration. It usually involves an application or a motion and approval by legal authorities. The rules of naturalization vary from country to country but typically include a promise to obey and uphold that country's laws and taking and subscribing to an oath of allegiance, and may specify other requirements such as a minimum legal residency and adequate knowledge of the national dominant language or culture. To counter multiple citizenship, some countries require that applicants for naturalization renounce any other citizenship that they currently hold, but whether this renunciation actually causes loss of original citizenship, as seen by the host country and by the original country, will depend on the laws of the countries involved.

Source: Wikipedia

Aggravated by 
(G) Very specific problems