A semicolon (;) is a punctuation mark that connects closely related ideas in a sentence. It can be used to link two independent clauses that could stand alone as separate sentences. For example, in the sentence "I love reading; it expands my imagination," the semicolon shows a strong relationship between the two thoughts. Additionally, semicolons can be used in complex lists where items contain commas. For instance, "On our trip, we visited Paris, London, and Rome; enjoyed local cuisine; and met new friends." Here, the semicolon helps clarify the list, making it easier to read and understand.