An alien is a citizen of any country other than the United States. A person who comes here to stay permanently is called an immigrant. Someone who intends to return to his or her country of origin is called a nonimmigrant, even if he or she intends to stay for a substantial period of time. For example, a student might stay in the United States many years to complete an education and still be considered a nonimmigrant. The distinction between immigrant and nonimmigrant is crucial.