In science, an "alien" is any organism that did not originate on Earth.
ArtI.S8.C18.8.7.2 Aliens in the United States - Constitution Annotated
: In the United States, once an alien gains admission and develops ties, their constitutional status changes, according them a "generous and ascending scale of rights". In science, an "alien" is any organism that
: Modern astronomers use telescopes to scan the atmospheres of distant planets for "biosignatures"—gases like oxygen and methane that might indicate life.
: In a legal context, an alien is a person in a country who is not a citizen of that country. : In a legal context, an alien is
The most famous "alien" in the world is the Xenomorph from the 1979 film Alien .
: The term is often used metaphorically in literature to describe the feeling of being "not quite one of us" or surviving in a foreign land. 3. Pop Culture and Science Fiction : In a legal context
Outside of space, "alien" has a specific legal meaning regarding human movement and national borders.