When phrases with the same words are combined by "and"/"or"

How are phrases with the same words joined by the conjunctions "and" and "or" to avoid repeating the same ones? If I intend to say sentence 1 below, which of sentences 2 to 5 has/have the same meaning?

1. What are the differences between the North Pole and the South Pole?
2. What are the differences between the North and the South Pole?
3. What are the differences between the North and the South Poles?
4. What are the differences between the North and South Pole?
5. What are the differences between the North and South Poles?

Would you rewrite the following sentences to make them more concise?

• There are a red flag and a blue flag.
• South Korea and North Korea are located on the Korean Peninsula.
• Which continent is bigger, North America or South America?

Thank you.

The only one that is well formed is [5].

From a syntactic point of view, you would typically coordinate constituents. Thus, you would coordinate two noun phrases, two nouns, two adjective phrases, etc. Regardless of whether you take north to be a noun or an adjective the north is not a constituent here because the is a determinative functioning as a determiner in the NP headed by pole(s). Consequently, you shouldn't be able to coordinate the north and the south here. (You can, of course, coordinate them when north and south aren't functioning as modifiers in somebody else's NP). So that should rule out [2] and [3].

Now, if you are coordinating AdjPs within a singular NP, in most cases, the only interpretation is that both properties signified by the AdjPs belong to the item signified by the NP. That is the green and red car cannot mean "the green car and the red car" but can only mean "the car that is both red and green." In the case of poles, this is a nonsense because there are no poles that are both north and south. Yet, the very fact that it is nonsense helps us understand that reference is being made to two poles, not one. So the semantics goes some way towards saving the syntax. This makes [4] possible but questionable in this particular case, and impossible in most cases.

The structure of [5] is ambiguous when it comes to other cases (e.g., the red and green cars), but again, since there are no poles that are both north and south, the only way to understand this is if one pole is north and one is south.

If we go to the corpora, indeed, we find that [5] is most likely, [4] is attested, and [2] and [3] are rare or nonexistent.

If I intend to say sentence 1 below, which of sentences 2 to 5 has/have the same meaning?

1. What are the differences between the North Pole and the South Pole?
2. What are the differences between the North and the South Pole?
3. What are the differences between the North and the South Poles?
4. What are the differences between the North and South Pole?
5. What are the differences between the North and South Poles?

All of these are okay. Maybe some are better than others, but none of them are wrong.

I don't like 2 and 3, because when I see two "the"s I want to see two nouns, but that's just my personal preference.

Would you rewrite the following sentences to make them more concise?

• There are a red flag and a blue flag.

It should be, "There is a red flag." To understand why, rewrite it to make it less concise:

• There are a red flag and there are a blue flag. <-- wrong
• There is a red flag and there is a blue flag. <-- OK

Would I make it more concise? You can if you want, but I don't recommend it. "There is a red and a blue flag." is only a little bit shorter, and it's harder to read.

Of course, you mustn't write, "There is a red and blue flag." because that means there is one flag with two colors.

• South Korea and North Korea are located on the Korean Peninsula.

Hmm ... be careful.

Imagine that you are talking about two brothers, called John Smith and Bill Smith. Is it okay to call them "John and Bill Smith"? Of course!

Now, imagine that you are talking about two great politicians called John Smith and Bill Smith. They are not from the same family. In politics, they are enemies. Would you call them "John and Bill Smith"? Certainly not.

So what about North Korea and South Korea? Do you want to say they are like brothers?

• Which continent is bigger, North America or South America?

Again, you can abbreviate this if you want to, but I don't recommend it. When we put North America and South America together, we don't call them "America". ("America" means "The USA".) We call it "The Americas". We try to keep them separate in our language, because they are almost completely separate pieces of land.