What is the Latin word for alien?

The usual Latin words for “alien” are aliēnus, amīcus, aliēnigena; also advena, peregrīnus, hospes. The right choice depends on the sense; see the distinctions below.

English → Latin

“alien” in Latin

aliēnusOf that which belongs to another person, place, or object—of another, alien, foreign; unfriendly, inimical, hostile, sus amīcusfriendly, well-disposed, amicable; loyal, devoted to; supporting, propitious, helpful aliēnigenaforeign, alien advenaoutsider, foreigner, stranger, alien peregrīnusforeign, alien; exotic hospeshost; guest, visitor; stranger, foreigner indigenanative, indigenous exteron the outside, outward, external, outer, far, remote; of another country; foreign, strange externusoutward, external; foreign, alien, exotic, strange extrāriusoutward, external, extrinsic; unrelated (person); stray (canis extrarius)

The English word alien itself goes back to Latin alius, through aliēnus.

Riddle & Arnold A Copious and Critical English–Latin Lexicon, 1864

alien s.

Foreign to, alienus (not relating or belonging to me: opposed to meus or amicus): from anything, alicui rei, aliqua re, ab aliqua re: from anybody, alicui, ab aliquo. To be alien from, alienum esse, abhorrere a, etc.

alien s.

alienigena (born in a foreign country: opposed to patrius, indigena): advena (one who has come into the country from the country of his birth: opposed to indigena: but the proper opposite to advenae is aborigines, αὐτοχθόνες, the original inhabitants): peregrinus (one travelling or sojourning in a country, and therefore not possessing the rights of citizenship: the political name of a foreigner: opposed to civis): hospes (opposed to popularis: foreigner, but, as such, claiming from us the rights of hospitality). Observe, exterus and externus denote a foreigner, whether now in his own land or not: externus being a geographical, exterus mostly a political term: extraneus means what is without us: opposed to relatives, family, native country: extrarius, opposed to one’s self. All these, except hospes, are used adjectively. (The words are found in this connection and order), externus et advena (e.g., rex); alienigena et externus; peregrinus et externus; peregrinus atque advena; peregrinus atque hospes.

Quick answer

What is the Latin word for alien?: The usual Latin words for “alien” are aliēnus, amīcus, aliēnigena; also advena, peregrīnus, hospes. The right choice depends on the sense; see the distinctions below.

Entry from J. E. Riddle & T. K. Arnold, A Copious and Critical English–Latin Lexicon (rev. C. Anthon, New York: Harper, 1864), digitised by Fergus J. P. Walsh, CC BY-SA 4.0; Latin markup adapted by latindictionary.co.