South Korean nationality law details the conditions in which an individual is a national of the Republic of Korea (ROK), commonly known as South Korea. Foreign nationals may naturalize after living in the country for at least five years and showing proficiency in the Korean language. All male citizens between the ages of 18 and 35 are required to perform at least 18 months of compulsory military service. North Korean citizens are also considered South Korean nationals, due to the ROK's continuing claims over areas controlled by the Democratic People's Republic of Korea (DPRK).