English Reference

Word

alien

US/ˈeɪɫiən/

UK/ˈeɪliən/

Definitions

01extraterrestrial

B1 · Science

n. a creature from another planet.

n. a hypothetical or fictional being from a world other than Earth.

“The movie is about a friendly alien who gets lost on Earth.”

“Science fiction often explores how humanity might react to the arrival of an alien species with superior technology.”

Antonyms

earthling

02foreign national

B2 · Law

n. a person who lives in a country but is a citizen of a different country.

n. a person who is not a national or citizen of the country in which they are residing.

“The government issued new work permits for resident aliens.”

“The legal distinction between a resident alien and a naturalised citizen remains a central point of debate in immigration reform.”

Formal

Usage

In legal contexts, this term is precise, but in everyday speech, it can sometimes sound cold or unwelcoming.

Synonyms

foreignernon-citizen

Antonyms

03strange or unfamiliar

B2

adj. very strange and different from what you are used to.

adj. fundamentally different, inconsistent, or strange in nature; often used with the preposition 'to'.

“The idea of working in a big office was completely alien to him.”

“The harsh, industrial landscape felt entirely alien to the hikers, who were accustomed to the lush greenery of the valley.”

Antonyms

04to transfer property

C2 · Law

v. to give or sell the ownership of property to someone else.

v. to transfer the ownership of property or a right to another person.

“The owner decided to alien the land to a local charity.”

“The contract stipulated that the tenant could not alien the leasehold interest without the express written consent of the landlord.”

Formal · Technical

Usage

This is a transitive verb used almost exclusively in property law.

Synonyms

Real-World Examples

“The first time I listened to a soil soundscape, it felt like taking my first steps into an alien world.”
Aeon · 17 Aug 2026
“Its ways of thinking and problem-solving look alien to us.”
ScienceDaily · 14 Jul 2026
“What if evidence of alien life exists, but we simply fail to recognize it?”
ScienceDaily · 30 Jun 2026
“One example comes from the recent blockbuster "Project Hail Mary," which features a five-limbed alien with a rock-like exterior.”
ScienceDaily · 24 Jun 2026

Etymology

From Middle English alien, a borrowing from Old French alien, aliene, from Latin aliēnus (“belonging to someone else”, later “exotic, foreign”), from Latin alius (“other”), from Proto-Indo-European *h₂élyos. Related to English else.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

The word in film

Alien · 1979 · Sci-Fi

Directed by:
Ridley Scott
Starring:
Sigourney Weaver, John Hurt, Ian Holm

Ridley Scott's classic science fiction horror film follows the crew of a spaceship who encounter a deadly extraterrestrial life form. Sigourney Weaver stars as a survivor fighting to escape the dangerous creature before it destroys everyone on board.

Domain

Law

This entry

Level
C1 · Advanced
Frequency
Common
Updated

Scan code

englishreference.com/q/alien

English Reference