Fused sentences and comma splices

Start with two complete sentences

Correct: Maya missed the bus. She arrived late.

Both sentences are correct. Each has its own subject and finite verb and can stand alone as an independent clause.

In the first sentence, Maya is the subject and missed is the finite verb. In the second, she is the subject and arrived is the finite verb.

What happens when we join them incorrectly?

A fused sentence and a comma splice both contain independent clauses joined incorrectly. Here is what happens when we change the boundary between our two correct sentences.

Fused sentence: remove the full stop

Incorrect: Maya missed the bus she arrived late.

Removing the full stop and adding no joining word makes the clauses run together. This creates a fused sentence.

Comma splice: replace the full stop with only a comma

Incorrect: Maya missed the bus, she arrived late.

A comma alone does not correctly join these independent clauses in standard academic writing. This creates a comma splice.

A run-on is a problem with how clauses are joined. A long sentence can be correctly structured, and a short sentence can contain a comma splice.

Four ways to repair the boundary

Starting error: Maya missed the bus she arrived late.

The examples below repair this fused sentence. The same methods can repair the comma splice shown above.

1. Use a full stop

Maya missed the bus. She arrived late.

This presents the ideas as separate statements. Remember the capital letter after the full stop.

2. Use a comma and a coordinating conjunction

Maya missed the bus, so she arrived late.

So shows the result. But and yet express contrast, while and adds information. The coordinating conjunctions are for, and, nor, but, or, yet, so, sometimes remembered as FANBOYS.

The comma goes before the conjunction when it joins two independent clauses.

3. Use a semicolon

Maya missed the bus; she arrived late.

A semicolon connects closely related independent clauses. Both sides must be able to stand alone.

4. Make one clause dependent

Maya arrived late because she missed the bus.

Because makes the reason explicit. Other subordinating conjunctions can express time, contrast or a condition. Choose a word that matches the relationship you mean.

The “however” trap

Transitions such as however and therefore help show connections, but they do not join independent clauses in the same way as but or so.

Comma splice: The library was closed, however, we could return our books outside.

Correct: The library was closed; however, we could return our books outside.

Also correct: The library was closed. However, we could return our books outside.

When you edit, find the independent clauses first. Then check how they connect.

Try it: six questions

Identify the structure in the first three questions, then choose a correction. Check any answers you have selected. You can change your answers and try again.

1. The rain stopped we went outside. Complete sentence Fused sentence Comma splice

2. I checked my bag, my keys were missing. Comma splice Complete sentence Fused sentence

3. Although the journey took longer than expected, we arrived before the doors closed. Fused sentence Comma splice Complete sentence

4. Choose the correctly punctuated version. The library was closed, however, we could return our books outside. The library was closed; however, we could return our books outside. The library was closed however we could return our books outside.

5. Choose the correction that clearly shows the reason. We stayed indoors because the storm was getting worse. We stayed indoors, the storm was getting worse. We stayed indoors the storm was getting worse.

6. Choose the correctly joined sentence. Sam wanted to join the game, he had forgotten his trainers. Sam wanted to join the game but, he had forgotten his trainers. Sam wanted to join the game, but he had forgotten his trainers.