The term alien under the law refers to any particular individual that is in a country that is not a citizen of that country. An alien can therefore be categorized in various manners in accordance to the laws of a particular country. For example, an alien will sometimes have to opportunity to legally stay in the country under specific terms.
A legal alien can consist of tourists, individuals with student visas, and permanent legal residents. Therefore, any person in a country that does not meet such categories is considered to be an illegal alien. An illegal alien will be an individual that is not authorized to be in that country by law. Illegal aliens can sometimes be residing illegally within that country or have entered the country through illegal means. This can also include entering a country through unauthorized entry points and visa expiration.
In the United States, illegal aliens are simply defined as any person that is not born in the United States or is simply not a citizen of the country. The laws in the United States in regards to aliens have their history dating back to the late 18th century.
Though the term illegal alien is used quite often, other terms such as “unauthorized alien” or “illegal immigrants” are often times used in legislation both at the federal and state level. In the United States, being an illegal alien can have certain consequences, usually involving deportation to the illegal alien’s original country of citizenship or birth.