Comma Splices, Run-ons, & Sentence Fragments

Comma splices, run-ons, and sentence fragments are common sentence-level errors that interfere with clarity and readability in writing. This handout provides an overview of how to avoid and correct these errors. While this handout covers basic concepts, always work with your audience and assignment in mind.

Sentences and Clauses

Since comma splices, run-ons, and sentence fragments are all errors related to sentence boundaries and clauses, it is useful to understand complete sentences and different types of clauses.

• A complete sentence contains a subject and a verb (predicate) and forms a complete thought.
• A clause is a group of words that contains a subject and a verb (predicate).
• An independent clause has the same elements as a sentence (subject, verb, complete thought) and can stand alone as a sentence.
• A dependent clause contains a subject and verb but lacks a complete thought and cannot stand alone as a sentence.

What are Comma Splices and Run-ons?

A comma splice occurs when two sentences or independent clauses are joined together by a comma, while a run-on sentence occurs when two sentences or independent clauses are joined without proper punctuation. Sentences or independent clauses must be separated by punctuation other than a comma or by a comma with a coordinating conjunction (for, and, nor, but, or, yet, so).

• Comma Splice Example: Devi dislikes tea, it makes her feel sick. (comma splice)
• Run-On Example: My friend hates the beach she prefers the mountains. (run-on)

How to Correct Comma Splices and Run-ons

Both comma splices and run-ons are fixed using the same methods. These methods preserve the meaning of the text and ensure sentences, clauses, and punctuation are used properly.

Add a Period: Separate the two independent clauses with a period to make two complete sentences.

• Incorrect: My friends love the beach, they are from California.
• Correct: My friends love the beach. They are from California.

Add a Coordinating Conjunction: Use a coordinating conjunction (for, and, nor, but, or, yet, so) between two independent clauses to conjoin the clauses into one sentence. Add a comma before the conjunction.

• Incorrect: Devi was never very good at art, she bought a paint kit to learn.
• Correct: Devi was never very good at art, so she bought a paint kit to learn.

Add a Subordinating Conjunction: Add a subordinating conjunction (after, before, if, once, since, so that, although, where, while, unless, until, etc.) to the beginning of one independent clause to make it a dependent clause (a clause that cannot stand alone as a complete sentence). If you add an independent clause after the dependent clause, use a comma.

• Correct: Devi dislikes tea since she is allergic. (dependent clause + independent clause)
• Correct: Although my friend hates the beach, they are from California. (independent clause + dependent clause)

Add a Semicolon: When two independent clauses are closely related, connect them with a semicolon. Consider adding a conjunctive adverb (accordingly, however, meanwhile, therefore, furthermore, nevertheless, rather, etc.).

• Correct: I was never very good at art; however, I bought a paint kit to learn.
• Correct: Sasha read that a machine would do half his work; accordingly, he ordered two.

What are Sentence Fragments?

A sentence fragment is punctuated like a complete sentence, but a fragment lacks one or more of the elements necessary for a complete sentence.

• Sentence Fragment Example: Have been going to school regularly. (no subject)
• Sentence Fragment Example: The dog who lives next door. (no complete verb)
• Sentence Fragment Example: Because I love to read and write. (not a complete thought)

How to Correct Sentence Fragments

To fix a sentence fragment, identify what element or information is missing and add it to the sentence.

Add a Subject: Specify who or what is acting or being acted upon in the sentence.

• Incorrect: Have been going to school regularly.
• Correct: We have been going to school regularly.

Add a Complete Verb: Use the sentence fragment as the subject of the sentence and add a complete verb describing what the subject is doing.

• Incorrect: The dog who lives next door.
• Correct: The dog who lives next door barks loudly.

Complete an Incomplete Thought: Complete the thought by removing the subordinating conjunction (after, when, unless, while, even though, until, since, because, etc.) that makes the sentence a dependent clause (a group of words that cannot stand alone as a sentence). Another option is to add an independent clause (a group of words that contains a subject, verb, and complete thought and can stand alone as a sentence) before or after the dependent clause. If you add an independent clause after the dependent clause, use a comma

• Incorrect: Because I love to read and write (sentence fragment with an incomplete thought)
• Correct: I love to read and write. (subordinating conjunction removed)
• Correct: Because I love to read and write, I have a large library. (independent clause added)