To fix run-on sentences, find the complete thoughts that have been pushed together and connect or separate them with the right punctuation. When you are learning how to fix run-on sentences in academic writing, do not treat every long sentence as an error. A sentence becomes a run-on when independent clauses are joined incorrectly or receive no punctuation at all.
How to fix run-on sentences in academic writing
Start by locating the verbs. Each clause that has a subject and a verb and can stand alone is an independent clause. For example, “The survey included 200 students” is complete. “The results were inconsistent” is also complete. If you place both clauses in one sentence without a proper connection, you create a run-on.
There are two common forms. A fused sentence has no punctuation between independent clauses: “The survey included 200 students the results were inconsistent.” A comma splice uses only a comma: “The survey included 200 students, the results were inconsistent.” A comma alone cannot join two complete sentences.
The best correction depends on what you mean. Ask one simple question: What is the relationship between these ideas? One idea may add to the other, contrast with it, explain it, or show a cause and result. Your punctuation and word choice should make that relationship visible.
Use a period when the ideas need space
A period is often the clearest choice, especially when the second statement introduces a new point. This option also prevents an overloaded sentence from becoming hard to follow.
Run-on: The author uses several historical examples the evidence does not support her conclusion.
Revised: The author uses several historical examples. The evidence does not support her conclusion.
This revision is direct. It works well in research papers when each claim needs its own emphasis. Do not worry that periods make your writing look simple. Clear sentences are usually stronger than long sentences with unclear structure.
Use a comma and a coordinating conjunction
Use a comma followed by a coordinating conjunction when two complete ideas have a close, equal connection. The coordinating conjunctions are for, and, nor, but, or, yet, and so. You may remember them with FANBOYS, though the acronym matters less than the meaning.
Run-on: The sample size was limited, the researchers reported their findings cautiously.
Revised: The sample size was limited, so the researchers reported their findings cautiously.
Here, “so” signals a result. “But” signals contrast: “The source is recent, but it does not address the research question.” “And” adds a related idea: “The data were collected in April, and the analysis began in May.” Do not add a conjunction automatically. Pick one that accurately describes the logic.
Use a semicolon for closely related complete thoughts
A semicolon joins two independent clauses without a coordinating conjunction. It tells readers that the ideas are closely connected, but each clause still has enough weight to stand on its own.
Run-on: The policy changed after the protest many students still did not know about it.
Revised: The policy changed after the protest; many students still did not know about it.
Semicolons can be useful in academic writing, but they are easy to overuse. If the clauses are only loosely related, use a period instead. If you need to state the relationship plainly, use a conjunction or a transition word.
Use a dependent clause when one idea explains the other
You can also make one clause dependent by adding a subordinating word such as because, although, while, since, if, or when. This approach works when one thought depends on the other for its full meaning.
Run-on: The experiment was repeated the first trial produced unusual results.
Revised: The experiment was repeated because the first trial produced unusual results.
The word “because” explains cause. Other choices change the meaning. “Although the first trial produced unusual results, the experiment was not repeated” creates contrast. Read the revised sentence carefully. Grammar may be correct even when the connector gives the wrong relationship.
Choose punctuation based on meaning
Writers sometimes fix run-ons by inserting punctuation at random. That may remove one error while creating a confusing sentence. Consider these different revisions:
- The interviewees disagreed. The researcher revised the question.
- The interviewees disagreed, so the researcher revised the question.
- The interviewees disagreed; the researcher revised the question.
- Because the interviewees disagreed, the researcher revised the question.
All four versions are grammatically possible. They do not say exactly the same thing. The second and fourth versions make the cause-and-effect relationship explicit. The first leaves the connection for the reader to infer. The semicolon suggests a close connection without naming it.
Use a quick revision process
When you edit a draft, read one paragraph at a time and mark every subject-verb pair. Then check whether you have placed two complete clauses side by side. If you have, decide whether the ideas should become two sentences or remain connected.
- Find the first complete clause.
- Find the next complete clause.
- Check the punctuation between them.
- Choose a period, a semicolon, or a comma plus a suitable conjunction.
- Read the sentence aloud and confirm that the connection matches your meaning.
Reading aloud can help because run-ons often sound rushed. Still, sound is not enough. Some long sentences sound smooth but contain a comma splice. Check the clause structure, not only the rhythm.
Errors to avoid when revising
Do not fix a comma splice by deleting the comma and leaving the clauses together. That turns it into a fused sentence. Also avoid putting a semicolon before a dependent clause. This is incorrect: “The results were excluded; because the measurements were incomplete.” The word “because” makes the second part dependent, so use a comma instead.
Be careful with transition words such as however, therefore, and consequently. These words do not work like coordinating conjunctions. A comma alone is not enough: “The evidence was limited, however, the claim remained popular” is a comma splice. Use a semicolon and a comma, or split the sentence: “The evidence was limited; however, the claim remained popular.”
Finally, do not join unrelated claims simply to make your writing sound more advanced. Academic writing values precision. Two short sentences may communicate a complicated idea better than one crowded sentence.
Frequently asked questions
Are all long sentences run-on sentences?
No. A long sentence can be correct if its clauses are connected with proper punctuation and clear logic. Length is not the problem. Incorrectly joined independent clauses are the problem.
Can I use semicolons in a college essay?
Yes, if a semicolon joins two closely related independent clauses. Use it sparingly and only when you can explain why a period or conjunction would be less accurate. A semicolon cannot repair every long sentence.
Is a comma splice always wrong in academic writing?
In formal academic writing, treat a comma splice as an error. Replace the comma with a period or semicolon, or add a coordinating conjunction after the comma. Some creative writing uses comma splices for voice, but that choice rarely fits an academic assignment.
Should I use a grammar checker to find run-on sentences?
A grammar checker can flag possible run-ons, but review each suggestion yourself. Tools may mistake a deliberately structured long sentence for an error, and they may not choose the connector that best matches your argument. Your meaning should guide the final revision.
This article is for general informational purposes only and is not academic, admissions, or legal advice. Tool features, detection accuracy, and academic integrity policies change, so always verify current guidelines with your school or the official tool provider before making a decision.