The term "alien" is derived from the Latin alienus, meaning stranger, foreign, etym. "belonging (somewhere) else".
Different countries around the world use varying terms for aliens. The following are several types of aliens:
- a legal alien is a foreign national who is permitted by law to be in the host country. This is a very broad category which includes permanent residents, temporary residents, and visa holders or foreign visitors.
- a resident alien is a person who has permission by the government to reside and work in the country.
- a nonresident alien is a foreign national who is visiting a country as a tourist (e.g., for pleasure, for studies, on business, to receive medical treatment, to attend a conference or a meeting, as entertainers or sportspeople, and so forth).
- an illegal alien or undocumented alien is any foreign national inside a country where he or she has no legal right to be. It covers a foreign national who has entered the country through illegal migration. In some countries it also covers an alien who entered the country lawfully but subsequently fallen out of that legal status.
- an enemy alien is a foreign national of a country that is at war with the host country.