Grammar
Run on sentences: repair joined sentences
The doors opened everyone hurried inside. Each part is a complete idea, but the sentence does not show how the parts connect. It is a run-on sentence.
Identify run-on sentences and repair them by separating or correctly linking complete clauses without changing the intended relationship between the ideas.
Read and practice
Read the examples and try the written questions in this guide. Listening recordings are not available for this lesson yet.
Try the written questions
The road was closed, so we took the train. /ðə rəʊd wəz kləʊzd, səʊ wiː tʊk ðə treɪn/
The short answer
Repair a run-on sentence by making separate sentences, using a comma with a coordinating conjunction, using a semicolon between closely related clauses, or making one clause dependent. Do not use a comma alone to join two complete clauses.
The doors opened, and everyone hurried inside.
Why it works: The comma and and join two complete clauses. The second clause follows the first event.
5 more examples
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The meeting ended the group packed their bags.
The two complete clauses have no correct join.
Not this:The meeting ended
, andthe group packed their bags. What changes: The conjunction joins the completed meeting to the next action. -
The road was closed, we took the train.
This is a comma splice. Each side can be a sentence by itself.
Not this:The road was closed
, sowe took the train. What changes: So shows that taking the train was the result of the road closure. -
The files are ready send them to Marta.
The first clause is a statement and the second is an instruction. They need a clear boundary.
Not this:The files are ready
.Send them to Marta. What changes: A full stop is a simple repair when each idea can be its own sentence. -
The museum was closed, however, we still walked around the gardens.
A comma cannot join complete clauses around however.
Not this:The museum was closed
; however,we still walked around the gardens. What changes: The semicolon joins the clauses, and however signals a contrast. -
The rain stopped we continued the match.
The ideas are connected by time, but the sentence does not show that connection.
Not this:
When the rain stopped, we continued the match. What changes: When makes the first idea a time clause and clearly links it to the result.
Read the full guide
Start by testing each side of the join. In The printer stopped we used the copy room, The printer stopped is complete and we used the copy room is also complete. The writer must show the connection. A full stop makes two sentences. A conjunction, semicolon, or dependent clause can keep the ideas in one sentence.
Find the complete clauses
Look for a subject and a verb. If a group of words can stand alone as a sentence, it is an independent clause. A run-on sentence often has two of them pushed together. The problem is the join, not the length.
The bus arrived the passengers got on.
The bus arrived is complete. The passengers got on is also complete. The writer must show how the clauses connect.
The bus arrived. The passengers got on.
A full stop gives each complete idea its own sentence.
Can the words the screen went dark stand alone as a sentence?
Yes. The screen is the subject and went dark is the verb phrase, so it is a complete clause.
Use a full stop for separate ideas
A full stop is often the clearest repair. Use it when each clause has its own point, or when you do not need to show a particular relationship. Check that the new sentence begins with a capital letter.
I called the clinic they offered an appointment on Monday.
Both parts are complete clauses, but they are joined with no punctuation.
I called the clinic. They offered an appointment on Monday.
The full stop separates the two actions cleanly.
Repair: The package arrived I opened it at once.
Write The package arrived. I opened it at once. This repair makes two complete sentences.
Use a comma with a coordinating conjunction
A coordinating conjunction can join two independent clauses. Common choices are and for addition, but or yet for contrast, or for a choice, and so for a result. Put a comma before the conjunction when both sides are complete clauses.
The train was crowded, but we found two seats.
The train was crowded and we found two seats are complete clauses. But shows the contrast between them.
The train was crowded, so we stood near the door.
So introduces the result of the crowded train.
Which word fits a result: and, so, or but?
Use so when the second clause is the result of the first clause.
Do not use a comma alone
A comma alone cannot join two independent clauses. This error is called a comma splice. Add a coordinating conjunction after the comma, change the comma to a full stop, or choose another correct repair.
The workshop finished, we collected our notes.
The comma separates the clauses, but it does not explain the connection or create a correct sentence.
The workshop finished, and we collected our notes.
The comma and and now form a correct join between the two clauses.
What is wrong with I lost my card, I paid in cash?
It is a comma splice. Both I lost my card and I paid in cash can stand alone, so the comma needs a conjunction or a different repair.
Use a semicolon for closely related clauses
A semicolon can join two independent clauses that are closely related. It creates a stronger pause than a comma and a weaker break than a full stop. Do not use a semicolon before a clause that cannot stand alone.
The kitchen was already clean; nobody needed to wash the dishes.
Each side is a complete clause, and the second explains the practical result of the first.
The kitchen was already clean. Nobody needed to wash the dishes.
A full stop is also correct. Choose the semicolon only when you want to keep the close connection visible.
Can a semicolon join We missed the bus and because the station was crowded?
No. Because the station was crowded is dependent and cannot stand alone as the second side of a semicolon.
Make one clause dependent when the meaning needs it
Sometimes one clause gives a reason, time, condition, or contrast. A subordinating conjunction makes that relationship clear. Use because for a reason, when for time, if for a condition, and although for a contrast.
The shop was closing we paid quickly.
The ideas are related, but the reader cannot tell whether the first clause gives a reason, a time, or another connection.
Because the shop was closing, we paid quickly.
Because makes the first clause a reason. The comma separates it from the main clause.
Choose a word for time: because, when, or although.
Use when for time. For example, When the alarm rang, I left the building.
Before you go
Remember this
A run-on sentence needs a clear join between complete clauses. Find the clauses first. Then use a full stop, a comma with a coordinating conjunction, a semicolon for closely related ideas, or a dependent clause that shows the relationship. Read the repair aloud to check that each idea is easy to follow.
Practice with the written examples
You can practice with the written questions in the Learn tab. Each answer includes an explanation.
Try the written questionsListening test not available yet
This lesson does not have the recordings needed for a listening test. Use the written questions in the guide to check your understanding.
Try the written questionsQuestions about "Run on sentences: repair joined sentences"
What is a run-on sentence?
A run-on sentence joins two or more independent clauses without correct punctuation or a suitable linking word. It can be short or long. The problem is that the reader cannot see the boundary or relationship between the complete ideas.
The meeting ended the group packed their bags.
Is a run-on sentence the same as a long sentence?
No. A long sentence can be correct when its clauses have clear punctuation and links. A short sentence can be a run-on when it pushes complete clauses together, as in The lights went out everyone became quiet.
The meeting ended, and the group packed their bags.
What is a comma splice?
A comma splice is a run-on sentence that uses only a comma to join independent clauses. For example, We missed the exit, we turned around needs a full stop, a semicolon, or a comma with a coordinating conjunction such as so.
The road was closed, we took the train.
When can I use a semicolon?
Use a semicolon between two independent clauses that are closely related. Both sides must be able to stand alone. For example, The store was closed; we returned the next day. A full stop is also correct in many cases.
The road was closed, so we took the train.
How do I choose between and, but, and so?
Use and to add information, but to show a contrast, and so to show a result. Check that each side has a subject and verb before you use a comma and one of these conjunctions to join the clauses.
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