What can a semicolon replace?
A semicolon is often used to replace a coordinating conjunction like 'and' or 'but'. The sentence about Sandip could have been written like this: "Sandip spent three hours in the library but he couldn't find the book he wanted."
What punctuation mark can replace a comma?
Semicolon. The semicolon is most commonly used to mark a break that is stronger than a comma but not as final as a full stop. It's used between two main clauses that balance each other and are too closely linked to be made into separate sentences.