English Reference
noun · adjective · verb

alien

n. · adj. · v.
US /ˈeɪɫiən/ UK /ˈeɪliən/ alien UK spelling alien's, alien's, aliened, aliening

  1. 01 B1 Intermediate Science

    n.a creature from another planet.

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

    Simple

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

    In context

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

    earthling
  2. 02 B2 Upper Intermediate Formal 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.

    Simple

    The government issued new work permits for resident aliens.

    In context

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

    Usage

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

    foreignernon citizen
  3. 03 B2 Upper Intermediate

    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'.

    Simple

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

    In context

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

  4. 04 C2 Proficiency FormalTechnical 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.

    Simple

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

    In context

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

    Usage

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

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

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.

This entry
Origin ine-pro *h₂élyos
Level C1 · Advanced
Frequency Common
Updated