"Is this seat taken?" means you wonder whether an empty seat is being held for someone who hasn't yet sat in it. For example, maybe one member of a couple arrived before the other one. "Is this seat empty?" just means "Is there anything currently on this chair?" and that's something you can know without asking. That's why the question doesn't sound natural. You could say "I found empty seats over there" for unoccupied seats. It sounds natural. I might also say something like "There are still seats over there" (empty is implied) or "There are open seats over there." I hope that helps!

I agree with most of the others. The seat being empty simply means nobody is actively occupying it, which is unrelated to whether or not the seat is reserved or available. It isn't rude to say "Is this seat empty?". The question is well-formed, but "empty" is not the most accurate word for what you're trying to ask. Regardless, I think people would understand that you meant "available."

Wow,I learned a lot of from your comments🫶

Yes, you're correct! When asking if a seat is available in places like cafes, common phrases include: "Is this seat taken?" "Are there any available seats?" As for your question about "Is this seat empty?" it is grammatically correct, but it may sound a bit less common or natural in everyday conversation. People generally prefer using the first two phrases mentioned above. Regarding your second question, saying "I found empty seats over there." is absolutely correct and natural. This phrase effectively communicates that you've discovered unoccupied seats and is commonly used in various contexts.

"Is this seat empty?" is a natural question but it might be rude. The fact that the seat is empty does not mean that you have permission to take it. It is more polite to ask "Is this seat available?" because it opens up the possibility of refusal without explanation.