2.2 Run-ons and Comma Splices

Introduction to Independent Clauses

To effectively spot and correct run-on sentences and comma splices, you must be completely comfortable identifying independent clauses. As discussed in the previous section, an independent clause is a group of words that contains a subject, a working verb, and expresses a complete thought. It can stand alone as a perfectly grammatical sentence.

When writing, we frequently want to connect multiple independent clauses to show relationships between ideas, improve the flow of our writing, and avoid choppy, simplistic sentences. However, the English language has strict rules about how independent clauses can be joined. If you fail to use the proper punctuation and conjunctions when linking these clauses, you will create a major grammatical error: either a run-on sentence or a comma splice. The PERT Writing exam will vigorously test your ability to recognize and correct these specific punctuation errors.

What is a Run-on Sentence?

A run-on sentence, also known as a fused sentence, occurs when two or more independent clauses are jammed together without any punctuation or connecting words between them. A run-on is not necessarily a long sentence; length has nothing to do with it. A very short sentence can be a run-on if it contains two improperly joined independent clauses.

Incorrect (Run-on): The concert ended the crowd cheered loudly.

Let's break this down. The first independent clause is "The concert ended" (Subject: concert, Verb: ended). The second independent clause is "the crowd cheered loudly" (Subject: crowd, Verb: cheered). Because there is absolutely no punctuation separating these two complete thoughts, they crash into each other, creating a fused sentence.

Run-on sentences confuse readers because they do not provide the necessary visual cues (like periods or commas) that indicate where one idea ends and the next begins. When reading a run-on, the reader is forced to backtrack and figure out the logical boundaries of the sentence.

What is a Comma Splice?

A comma splice is a very specific type of run-on sentence. It occurs when a writer attempts to join two independent clauses using only a comma. While commas are incredibly useful punctuation marks, they are grammatically too "weak" to hold two complete sentences together on their own.

Incorrect (Comma Splice): The weather was perfect for a picnic, we packed sandwiches and headed to the park.

In this example, "The weather was perfect for a picnic" is an independent clause. "We packed sandwiches and headed to the park" is also an independent clause. Placing a solitary comma between them is a comma splice error.

Many students make this error because they naturally pause between the two ideas when speaking, and they translate that vocal pause into a comma on the page. However, in written English, a comma alone is never sufficient to join two independent clauses. You must use stronger punctuation or add a conjunction.

Four Methods to Correct Run-ons and Comma Splices

Fortunately, whenever you encounter a run-on or a comma splice, you have four distinct, grammatically correct methods to fix it. The method you choose will depend on the logical relationship between the two clauses and the stylistic flow of your writing.

Method 1: Use a Period and a Capital Letter

The simplest way to fix a run-on or comma splice is to separate the two independent clauses into two distinct sentences. This is highly effective when the clauses are long or when you want to create a strong pause for emphasis.

Error: The engine started making a strange noise, I immediately pulled over to the shoulder. Correction: The engine started making a strange noise. I immediately pulled over to the shoulder.

Method 2: Use a Semicolon

A semicolon (;) is specifically designed to join two independent clauses that are closely related in meaning. It acts as a bridge, stronger than a comma but not as final as a period. You do not capitalize the word immediately following a semicolon unless it is a proper noun.

Error: My sister prefers studying in absolute silence I need background music to concentrate. Correction: My sister prefers studying in absolute silence; I need background music to concentrate.

You can also use a semicolon paired with a conjunctive adverb (like however, therefore, moreover, nevertheless) to clarify the relationship between the clauses. In this case, place a comma after the conjunctive adverb. Correction with Conjunctive Adverb: My sister prefers studying in absolute silence; however, I need background music to concentrate.

Method 3: Use a Comma and a Coordinating Conjunction (FANBOYS)

A comma can join two independent clauses if—and only if—it is followed by a coordinating conjunction. You can remember the seven coordinating conjunctions using the acronym FANBOYS:

• For: Shows reason or purpose (similar to 'because')
• And: Connects two related thoughts
• Nor: Joins negative statements
• But: Shows contrast
• Or: Presents an alternative or choice
• Yet: Shows concession or surprise (similar to 'but')
• So: Indicates a result or consequence

Error: The restaurant was incredibly busy, we decided to eat at home. Correction: The restaurant was incredibly busy, so we decided to eat at home.

Remember, both the comma and the FANBOYS word are required. Using just the comma creates a comma splice, and using just the FANBOYS word creates a run-on.

Method 4: Use Subordination

The final method is to turn one of the independent clauses into a dependent clause by adding a subordinating conjunction (like because, although, if, since, while). This creates a complex sentence and establishes a clear relationship between the ideas.

Error: The exam was extremely difficult, most students managed to pass. Correction: Although the exam was extremely difficult, most students managed to pass.

Quick-Reference Correction Table