In Warhammer 40,000, the Imperium of Man uses "xenos" as a catch-all term for any non-human life forms. For example, the Ordo Xenos is the branch of the Inquisition which deals with aliens, and they have whole litanies about what happens to Xenos they get their hands on, like "Mark of the Xenos" (also the name of a Deathwatch supplement).
Please note that "Xenos" is the plural AND singular spelling of the noun and adjective. This practise of using the unified form of this term for both singular and plural is inconsistent with the actual declension of 'xenos', which takes Greek inflections to reflect case and number as a noun, and case, number, and gender as an adjective. The technical plural form of 'xenos' in the nominative is 'xenoi' and accusative as 'xenon.' "xeno-" is a prefix used to denote the xenos origin of something, and Xeno is a character from Tau Quest whose name derives from "xeno-abomination".
If a scenario like that of Alien Nation or Men in Black happened in which extraterrestrials come to Earth in search of citizenship, the word Xenos would quickly become listed as Hate Speech due to the actions of /tg/.
- Dark Eldar
- Monstergirls, which is what happens when xenos meet Rule 34.
- Skaven, apparently.
- Old Ones