Sentence Fragments, Comma Splices and Run-on Sentences

Sentence fragments, comma splices, and run-on sentences are grammatical and stylistic bugs that can seriously derail an otherwise polished academic paper. Learn how to identify and eliminate these errors in your own writing here.

Sentence Fragments

A sentence fragment is just another term for 'incomplete sentence.' As the name indicates, it's merely a piece of a sentence that can't stand on its own. As you might remember, all sentences need to have at least one independent clause - that's a clause with at least one subject and one verb that can stand on its own as a sentence. So the best way to determine if your sentence is a fragment is to try to find this independent clause. If there isn't one, voila - an undercooked egg of a sentence.

Okay, so how to find the independent clause? Remember that the subject is the person, place, idea, or thing that is either doing something or being something in the sentence. Find the main subject first by finding the verb - that's the part of the sentence that creates the action - and then determine what that verb is relating to. For instance, Desmond was haunted by a small, sword-wielding ferret. The action here is 'was haunted' - the main verb being 'haunted' - while the thing being haunted is Desmond - that's the primary subject. Here's the same sentence in fragments.

Desmond was haunted. Okay, that part's a complete sentence.

By a small, sword-wielding ferret. The second sentence is a fragment because it no longer contains a main verb or subject. We have the subject of 'sword-wielding ferret,' but it's hanging out on its own. Sentence fragments usually lack either a main verb or a subject (or both).

Here's an example of a fragment missing its subject:

Withholding his allowance for blowing up the car.

To correct it, we need to explain who is withholding what. The parents were withholding his allowance for blowing up the car. would be one example, because you've added both the subject ('parents') and verb ('were') to make the sentence complete.

What's particularly confusing about sentence fragments is that you see them all the time when reading news stories or fiction because a sentence fragment can be very effective for conveying a certain style or mood. Take this paragraph from a short story by contemporary fiction writer George Saunders, which contains a mix of sentence fragments and short sentences to help give the reader a certain impression of the narrator:

Oops. Missed a day. Things hectic. Will summarize yesterday. Yesterday a bit rough. While picking kids up at school, bumper fell off Park Avenue. Note to future generations: Park Avenue = type of car. Ours not new. Ours oldish. Bit rusty.

Here's the same paragraph now with all the fragments made un-fragmented:

Oops. I missed a day. Things got hectic. I will summarize yesterday. Yesterday was a bit rough. While I was picking kids up at school, bumper fell off Park Avenue. Note to future generations: Park Avenue = type of car. Ours is not new. Ours is oldish. It's a bit rusty.

Notice how making the sentences grammatically correct gives the paragraph a completely different tone and changes the way the reader perceives the narrator. I'm bringing this up because I don't want you to distrust me when you see sentence fragments in the wild. The rule is: when you're writing academic essays, stay away from fragments; when writing fiction, then you can feel free to experiment a little bit more.

Run-On Sentences

Let's check out run-ons. A run-on sentence, or fused sentence, is a sentence that's missing the right punctuation to make it flow properly. A run-on occurs when what could be two complete sentences - that is, two independent clauses - are connected in one sentence without being punctuated. In other words, they're fused together instead of each clause being distinguished from the other. Here's an example of a run-on:

Clark had vanished he left his eyeglasses and coat in the telephone booth.

You have two independent clauses here, Clark had vanished and He left his eyeglasses and coat in the telephone booth. To make this a proper sentence and not a run-on, you must add proper punctuation. You have several different options - which you choose is a matter of your personal style and how you want to make the sentence look and feel to your reader.

You can add a comma and a coordinating conjunction. You can remember coordinating conjunctions by the mnemonic FANBOYS - that's for, and, nor, but, or, yet, and so. So:

Clark had vanished, but he left his eyeglasses and coat in the telephone booth.

You can make the run-on into two separate sentences:

Clark had vanished. He left his eyeglasses and coat in the telephone booth.

Or you can add a semicolon:

Clark had vanished; however, he left his eyeglasses and coat in the telephone booth.

The choice is yours, and it doesn't really matter which you choose as long as you've fixed the run-on.

One other thing to remember is that even though we tend to think of run-ons as sentences that are too long, a run-on is really defined by improper punctuation. I sang I danced. - despite being just four words - is a run-on sentence.

Comma Splices

Technically, a comma splice is a kind of run-on sentence, but they're harder to spot, so we're giving them their own section. A comma splice occurs any time a comma is inserted between two main clauses without a coordinating conjunction to connect them. For instance:

Most of us liked to eat fish, Jerry preferred to devour the still-beating hearts of fresh artichokes.

A sentence like this sounds fine when you read it out loud and it even looks pretty okay when you see it on the page, but it's wrong. If you're going to use a comma to separate these two independent clauses, you need to insert a coordinating conjunction (that's FANBOYS like we talked about a little bit earlier) after the comma, making the sentence, for instance:

Most of us liked to eat fish, but Jerry preferred to devour the still-beating hearts of fresh artichokes.

Because a comma splice occurs between two independent clauses, you can also remove the comma and replace it with a period (making two separate sentences) or a semicolon, like so:

Most of us liked to eat fish; Jerry preferred to devour the still-beating hearts of fresh artichokes.

The most basic thing to remember about comma splices is that they're really just a misused comma where other punctuation would be more appropriate.