Non-citizens

In law, an alien is a person who resides within the borders of a country and is not a national of that country, though definitions and terminology differ to some degree.

The term "Alien" is derived from the Latin alienus, meaning stranger, foreign, etym. "belonging (somewhere) else".

Different countries use varying terms for "aliens" including:

An "alien" in English law was someone who was born outside of the monarch's dominions and who did not have allegiance to the monarch. Aliens were not allowed to own land and were subject to different taxes to subjects. This idea was passed on in the Commonwealth to other common law jurisdictions.

In Australia, citizenship is defined in the Australian nationality law. Non-citizens living in Australia are either permanent residents; temporary residents; or illegal residents (technically called "unlawful non-citizens"). Most non-citizens (including those who lack citizenship documents) travelling to Australia must obtain a visa prior to travel. The only exceptions to this rule are members of the British royal family, and holders of New Zealand passports and citizenship who may apply for a visa on arrival according to the Trans-Tasman Travel Arrangement.

The British Nationality Act 1772 regulated who was to be called a British national.

The Aliens Act 1905, the British Nationality and Status of Aliens Act 1914 and the Aliens Restriction (Amendment) Act 1919 were all products of the turbulence in the early part of the 20th century.

...
Wikipedia