Grammar and Punctuation Rules

A run-on sentence occurs when two independent clauses are combined without proper punctuation or conjunctions. This can happen in two different ways:

Fused Sentence: two independent clauses mashed together with no punctuation.

• I love to read and I have so many books.

In this example, there are two complete sentences:

• I love to read.
• I have so many books.

"And" is the conjunction, but the lack of punctuation makes the sentence a run-on.

Comma Splice: when there is a comma between two independent clauses, but no conjunction (FANBOYS--for, and, nor, but, or, yet, so)

• I ate dinner, it was too much food.

The two complete sentences are the following:

• I ate dinner.
• It was too much food.

The sentence has a comma but no conjunction, making it a comma splice.

Look at the sentence and ask the following:

1. Are there two or more complete thoughts? If you can break the sentence into separate full sentences, and each would make sense on its own, you might have a run-on sentence.
2. Are those complete thoughts joined correctly? If they are simply mashed together or connected with only a comma, it is most likely a run-on sentence or a comma splice.

Use the following comma splice as an example for correcting a run-on sentence: Jamie left the house, he forgot his backpack.

Use a period to separate independent clauses

• Jamie left the house. He forgot his backpack.

Use a semicolon if the clauses are related

• Jamie left the house; he forgot his backpack.

Use a comma and a coordinating conjunction (FANBOYS)

• Jamie left the house, but he forgot his backpack.

Use a subordinate conjunction, or make one clause dependent

• Even though he forgot his backpack, Jamie left the house.
• Jamie left the house even though he forgot his backpack.

Use a semicolon and conjunctive adverb

• Jamie left the house; however, he forgot his backpack.