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mid-14c., "strange, foreign," from Old French alien "alien, strange, foreign; an alien, stranger, foreigner," from Latin alienus "of or belonging to another, foreign, alien, strange," also, as a noun, "a stranger, foreigner," adjectival form of alius "(an)other" (see alias). Meaning "not of the Earth" first recorded 1920. An alien priory (c.1500) is one owing obedience to a mother abbey in a foreign country.
"foreigner, citizen of a foreign land," from alien (adj.). In the science fiction sense, from 1953.
Introduced to a region deliberately or accidentally by humans. Starlings, German cockroaches, and dandelions are species that are alien to North America but have become widely naturalized in the continent. Compare endemic, indigenous.
a foreigner, or person born in another country, and therefore not entitled to the rights and privileges of the country where he resides. Among the Hebrews there were two classes of aliens. (1.) Those who were strangers generally, and who owned no landed property. (2.) Strangers dwelling in another country without being naturalized (Lev. 22:10; Ps. 39:12). Both of these classes were to enjoy, under certain conditions, the same rights as other citizens (Lev. 19:33, 34; Deut. 10:19). They might be naturalized and permitted to enter into the congregation of the Lord by submitting to circumcision and abandoning idolatry (Deut. 23:3-8). This term is used (Eph. 2:12) to denote persons who have no interest in Christ.