Fixing Run-On Sentences and Fragments for Good
Two of the most common sentence errors, and the simple checks that catch them before a reader or grader does.
Two Errors at Opposite Ends
Run-on sentences and fragments are the two sentence errors that show up most often in student and professional writing alike. They sit at opposite ends of the same problem. A run-on crams too much into one sentence, stitching independent clauses together with nothing strong enough to hold them. A fragment does the opposite, offering a piece of a sentence that cannot stand on its own.
Both are easy to make and surprisingly easy to miss, because when you read your own work your brain fills in the connections. The reader, or the grader, does not have that advantage. The good news is that both errors follow predictable patterns, and a couple of simple checks catch almost all of them.
Run-Ons vs. Fragments
| Feature | Run-on sentence | Sentence fragment |
|---|---|---|
| What goes wrong | Two full sentences joined improperly | A partial thought punctuated as a sentence |
| Common cause | Comma splice or no punctuation at all | Missing subject, verb, or main clause |
| How it reads | Breathless and rambling | Incomplete or hanging |
| Quick fix | Split into two sentences or add a conjunction | Attach to a neighboring sentence or add the missing part |
Why Run-Ons Happen
A run-on usually starts when a writer has two related thoughts and trusts the reader to follow the connection. So they string the thoughts together with a comma, or with nothing at all. The comma version, called a comma splice, is the most common: I finished the report, I sent it to my manager. Two complete sentences, joined only by a comma.
The trouble is that a comma is not strong enough to glue two full sentences together. You need either a period, which splits them, or a conjunction like and, but, or so, which links them with proper support. A semicolon also works when the two sentences are tightly related.
Read the sentence out loud. If you run out of breath before you reach a natural stopping point, it is probably too long. If you find yourself wanting to pause hard but there is only a comma, you likely have a comma splice. Split it there.
Three Ways to Fix a Run-On
- Put a period between the two independent clauses and start a new sentence.
- Add a coordinating conjunction like and, but, so, or yet after the comma.
- Use a semicolon when the two clauses are closely related and you want to keep them together.
Why Fragments Happen
Fragments usually come from editing. You cut a sentence down for impact, or you split a long sentence into two, and a dependent piece ends up standing alone. Because the fragment reads like part of a sentence, it can slip past you, especially when it starts with a transition word like because, although, or when.
The test for a fragment is whether the sentence can stand alone as a complete thought. If you read it in isolation and it leaves you waiting for more, it is a fragment. Because the project ran late is a fragment. It needs a main clause to complete it, like Because the project ran late, we missed the deadline.
A Reliable Two-Step Check
- 1Underline the subject and verb in each sentence
Every complete sentence needs a subject and a verb. If either is missing, you are looking at a fragment.
- 2Count the independent clauses in long sentences
If you find two or more full clauses joined only by a comma, you have a run-on. Fix it with a period, a conjunction, or a semicolon.
- 3Read slowly, one sentence at a time
Reading aloud forces you to notice where sentences end. This catches both breathless run-ons and hanging fragments that the eye glides over on a fast read.
The Patterns Worth Knowing
A sentence needs a subject, a verb, and the ability to stand alone. Give it a period when it is done, and a conjunction when it is not.
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