Becky is chatting with her classmate Lily in the common room of their dorm.

    Becky: Hi, Lily. What are you reading?

    Lily: Some science fiction short stories.

    Becky: Oh, I love sci-fi. Stories about the future, and advanced technology, and outer space--I love thinking about the possibilities.

    Lily: Me too. Especially since I'm an alien.

    Becky: What?

    Lily: Well, I wasn't born in this country. So, technically, I'm an alien.

    Becky: I guess you're right! After all, the word basically means "different" or "other."

    Lily: I've seen it as a verb and an adjective, too. Like "He felt alienated from the group" meaning he felt like he didn't belong.

    Becky: Yes. But it seems like these days, we usually use "alien" to mean "someone from another planet."

    Lily: I know! That's why I think it's funny to call myself that. But if I want to make it clear that I mean "visitor from another planet" and not just "foreigner," what can I say?

    Becky: Years ago, we called someone like that a "spaceman." Or, since many people believed Mars was inhabited, they would say Martian" or "man from Mars."

    Lily: Oh, yeah! Didn't they also talk about "little green men?"

    Becky: Sure! Also "men from outer space," "space beings," and "space inhabitants."

    Lily: And then there was that movie...

    Becky: That's right! "E.T.: The Extraterrestrial."

    Lily: I'm very familiar with the movie, but what does that word "extraterrestrial" mean exactly?

    Becky: Well, a scientific word for the Earth is "terra."

    Lily: We see it in words like "territory" and "terrain," right?

    Becky: Right. And "extra" can mean "outside of."

    Lily: Oh! So an "extraterrestrial being" or "extraterrestrial visitor" came from outside of Earth.

    Becky: Perfect!

    Lily: All right, then. How about us?

    Becky: Us?

    Lily: The people who aren't "extraterrestrial."

    Becky: Oh, you mean earthlings!

    Lily: Isn't that kind of a silly term?

    Becky: It does sound old-fashioned, but it serves the purpose. Usually, though, we just use "human" or "person" or other synonyms.

    Lily: I think in one sci-fi book I saw "terran."

    Becky: Yes, but that's a made-up word. Another sci-fi word is "tellurian."

    Lily: I guess we could just say "earth dweller" or something like that, right?

    Becky: We could. It's just all sort of silly, since the only life-forms we've met so far all dwell on earth.

    Lily: Got it. Well, see ya around, earthling!

    Becky: Bye, tellurian!