In The Big Bang Theory Season 3, Episode 4, Sheldon said that astro means star and Raj said astro means space, I got a little confused here, various websites and others are going 50-50 on the subject. What does astro actually means?

Raj: No, no, no, no! That rate is much too low for what we’d expect from this collision. Do you understand that we’re talking about dark matter colliding in outer space?

Sheldon: Of course I understand. And who are you to tell me about outer space?

Raj: I’m the astrophysicist. Astro means space.

Sheldon: Astro means star.

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    $\begingroup$ Why do you think it is an either or question? $\endgroup$ – samcarter Aug 22 at 12:18
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    $\begingroup$ Do you mean definitive in the sense of how it was used originally in Greek or what it is used for today? $\endgroup$ – called2voyage Aug 22 at 14:44
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    $\begingroup$ This might be better on English Language, as it is not about astronomy but about the meaning of prefix in the Language. $\endgroup$ – James K Aug 22 at 15:51
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    $\begingroup$ I'm voting to close this question as off-topic because the meaning can be easily found in a dictionary. $\endgroup$ – James K Aug 22 at 18:12
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    $\begingroup$ I'm voting to leave this question open because definitions of astronomy terms is absolutely on topic, and we shouldn't just use "off-topic" to close for any reason we feel like using it for. We have a terminology tag, let it be used. $\endgroup$ – uhoh Aug 22 at 23:09

Astro comes from the greek άστρο which not only means star but has a more general meaning that includes any small dot in the night sky (see https://en.wiktionary.org/wiki/%CE%AC%CF%83%CF%84%CF%81%CE%BF#Greek for details)

In today's language it still has a quite broad meaning:

Oxford English dictionary (https://www.oed.com/view/Entry/12240?isAdvanced=false&result=2&rskey=LlaQB9&):

Forming terms relating to stars, other celestial objects, or outer space.

Merriam Webster (https://www.merriam-webster.com/dictionary/astr-)

: star : heavens : outer space : astronomical

Conclusion: Sheldon and Raj are right


Astro definitely means star, hence astronomer, astrophysics,asteroid etc. Asteroid means star-like. Astronaut is a bit grandiose, as it means someone who journeys to the stars, which is something astronauts will never do. They have their work cut out to visit and explore some of the planets, asteroids and moons in our own solar system, and some of those will never be visited. No astronaut will ever land on Venus for example, though it is the nearest planet to us. To continue the star theme further, we also have asterisk, a star-like symbol, and aster, a kind of daisy, I'm sure there are more of them. The word comes from the Latin for star.

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    $\begingroup$ If it comes from Latin, then why do the Greeks knew astronomy? Latin did not exist at that time. You're wrong. $\endgroup$ – User123 Aug 26 at 15:14

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