When is a sentence not a sentence? When it’s a fragment (such as this one), a comma splice, or a run-on sentence. This is basic stuff that we all learned in elementary school, but it’s often helpful to revisit the basics.
A sentence is a sequence of words that expresses a complete thought. It is an independent clause that contains a subject and a verb. (Note: The subject can be implied, as in an imperative: Stop! The implied subject in this case is you.)
Correct: I woke this morning to the sound of light sabers clashing in the living room.
We get into trouble when we combine two complete thoughts into one sentence without using the appropriate punctuation or conjunction.
Incorrect: I woke I heard the sound of light sabers clashing in the living room.
The run-on sentence
A run-on sentence contains two or more independent clauses with no connector between them. If independent clauses are not separated into distinct sentences by a period, then they must be connected by a comma and a conjunction or by a semicolon.
Correct: I woke. I heard the sound of light sabers clashing in the living room.
Correct: I woke, and I heard the sound of light sabers clashing in the living room.
Correct: I woke; I heard the sound of light sabers clashing in the living room.
Remember that the length of a sentence does not determine whether the sentence is a run-on. Run-on sentences have structural flaws that can occur even in short sentences.
Incorrect: Looking at the mess they made I regretted sleeping in.
Correct: Looking at the mess they made, I regretted sleeping in.
Long sentences are not necessarily run-on sentences. Here is a 200-word sentence that is not a run-on.
The comma splice
Another type of run-on sentence is a comma splice. A comma splice is a sentence with a comma between the two independent clauses.
Incorrect: It’s time for school, put your light sabers away.
You correct a comma splice the way you would correct any run-on sentence. Separate the clauses into two sentences, or connect them with a comma and conjunction or with a semicolon.
Correct: It’s time for school, so put your light sabers away.
Correct: It’s time for school; put your light sabers away.
The fragment
A fragment is a sequence of words that is not a full sentence because it lacks a subject, a verb, or a complete thought.
Incorrect: The sound of light sabers clashing in the living room.
You correct a fragment either by adding a subject or a verb, or by making the sentence a complete thought.
Correct: The sound of light sabers clashing in the living room roused me from my warm bed.
In that example, The sound of light sabers clashing in the living room is the subject of the verb roused.
Readers, any real-life sentence gaffes you’d care to share?
A version of this article first appeared on Ragan Communication’s PR Daily.