What is a run-on sentence?

• A. A sentence that uses multiple adjectives.
• B. A sentence that contains a dependent clause.
• C. An interrogative sentence ends with a question mark.
• D. A run-on sentence occurs when two complete sentences are improperly joined without appropriate punctuation.

Answer: (D)

A run-on happens when two independent thoughts could each stand as a sentence, but they’re glued together without the right punctuation or connecting word. In other words, two complete clauses are joined improperly, so the sentence runs on without a clear break. Because each clause could form its own sentence, the lack of a period, semicolon, or a coordinating conjunction (like and, but, or) makes the writing hard to follow and grammatically off.

For example, “I finished my homework I watched TV” is a run-on. It can be fixed by adding a period or a semicolon, or by joining with a conjunction: “I finished my homework, and I watched TV.” The other choices describe different sentence features that aren’t about joining two complete thoughts, so they don’t define a run-on.