 Title 8 of the US Code is the portion of the law that contains laws on citizenship, nationality, and immigration.It defines the legal term Alien as "any person not a citizen or national of the United States".Terminology used in Title 8 includes illegal alien (33 times), unauthorized alien (21 times), undocumented alien (18 times), illegal immigrant (6 times), undocumented person (2 times) and others.