In the United States, an Alien is an individual who is not a citizen or national of the United States. Government use of the term Alien dates back to 1798, when John Adams signed the Alien and Sedition Acts into law. In general, immigrants are considered a subset of Aliens by the U.S. Government. There are several different ways that the term Alien is used, all denoting different immigration statuses: Deportable Alien, Inadmissible Alien, Nonresident Alien, Resident Alien and Undocumented Alien (also referred to as an Illegal Alien).
There is some discussion on whether using the term Alien is politically correct. For example, in 2009, a Halloween costume that came with a space alien mask and an orange jumpsuit with “Illegal Alien” stamped across the chest caused public uproar and was ultimately banned from Target stores.