Which punctuation mark is commonly used to connect independent clauses?

The semi-colon is the punctuation mark that is commonly used to connect independent clauses. An independent clause is a segment of a sentence that can stand alone as a complete thought, possessing its own subject and verb. When two independent clauses are related or closely connected in idea, using a semi-colon allows for a smoother transition between them than a period, which would create a stronger break.

For example, in the sentence "I have a big exam tomorrow; I can't go out tonight," the semi-colon indicates that the two clauses are related, while still maintaining their individual identities as separate complete thoughts. This is particularly useful in writing where the relationship or contrast between the clauses is important for clarity and coherence.

In contrast, using just a period would separate the clauses too distinctly, altering the flow and relationship of the ideas. A comma could be used to connect independent clauses, but it must be paired with a conjunction (e.g., "and," "but") to do so correctly, otherwise it would result in a comma splice, which is a grammatical error. An apostrophe is primarily used for showing possession or forming contractions and does not serve the function of connecting independent clauses.