Question

1. Julie could have bought the book.
2. Julie might have bought the book.
3. Julie could have bought the book, (but she borrowed it from the library instead.)
4. Julie could buy the book yesterday.
5. Julie was able to buy the book yesterday.
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Q1) It is sometimes confusing if #1 means #2 or #3? #2 means possibility. #3 means that anyway Julie didn't buy the book. What do you think about that? Does #1 mean #2 or #3?

Q2) #4 means #5, right?

Answer 1

1 and 2 mean about the same thing.

3 is fine if you remove the parentheses. This sentence gives details about what Julie did after she didn't buy the book. The other two don't.

4 and 5 mean about the same thing, but 5 is the better phrasing.