A fragment is a smaller part broken off from something larger. It is incomplete. Thus, a sentence fragment is a part of a sentence; it is a group of words not complete in itself, but incorrectly punctuated as if it could stand alone.
In order to be a sentence, a word group must meet three criteria: (1) it must contain a subject (2) it must have a verb, and (3) it must make a complete thought (that is, it must make sense by itself).
A sentence fragment is not a sentence because it does not meet these two criteria: either (1) it does not contain both a subject and a verb, or (2) it does contain a subject and verb but does not make sense by itself.
Fragments That Do Not Contain a Subject and a Verb
This type of fragment is often a phrase – that is, a group of words that go together to form a unit but that cannot function as a sentence. Sometimes, this type of fragment contains an ing word or an infinitive that looks like a verb, so the writer is deceived into thinking that a verb is present.
Examples:
(a) I opened the door. Expecting to see my brother standing on the porch.
Here, we have two word groups punctuated as sentences. The first one really is a sentence – it contains the subject I and the verb opened , and it makes a complete thought.
The second one, however, does not contain a subject or a verb. The word brother is a noun, which could certainly be used as a subject, but it is not acting as the subject of a verb here. One reason is that there is no verb to go with it.
The two ing words, expecting and standing , may look like verbs, but they are not. Remember that an ing word cannot be a verb unless it has a helper with it (for example, are expecting or was standing ). Similarly, to see may look like a verb, but it is an infinitive and cannot function as a verb. Therefore, there is neither a subject nor a verb in this word group. It is a fragment.
This fragment can be corrected in either of two ways – it can be attached to the sentence before by replacing the period with a comma, or it can be expanded to make a complete thought:
I opened the door, expecting to see my brother standing on the porch.
I opened the door. I was expecting to see my brother standing on the porch.
(b) With a sudden loud bang and a shower of multicolored sparks. The mixture exploded.
Once again, we have two word groups punctuated as sentences. The second one is a sentence because it contains the subject mixture and the verb exploded and makes a complete thought.
The first, however, is merely a long word group consisting of two prepositional phrases. Although there are many words, there is no subject or verb. Therefore, the word group is a fragment. In order to be correct, it needs to be attached to the sentence that comes after it:
With a sudden loud bang and a shower of multicolored sparks, the mixture exploded.

Fragments That Contain a Subject and a Verb
This type of fragment is usually a dependent clause. Every dependent clause contains a subject and a verb, but it does not make sense by itself. For example, consider the following word groups:
Donald was checking his trapline.
He saw an enormous black bear.
Both word groups contain a subject and a verb and make a complete thought; therefore, they are sentences.
However, if I put a subordinating conjunction in front of the first sentence, it will no longer make sense by itself.
While Donald was checking his trapline. He saw an enormous black bear.
The addition of the subordinating conjunction while has changed the first sentence into a dependent clause; it no longer makes sense by itself, so it cannot stand alone as a sentence. It is a fragment, even though it contains a subject and verb. Now it must be attached to the sentence which comes after it:
While Donald was checking his trapline, he saw an enormous black bear.
A dependent clause can also be formed with a relative pronoun, such as who or which.
Consider the following examples:
I have a lovely carved wooden box. Which a friend brought me from India.
Several years ago, I met a woman. Who had traveled around the world.
In both cases, the first word group is a sentence, while the second word group is a dependent clause beginning with a relative pronoun. The dependent clause does not make sense by itself and is therefore a fragment; in order to be correct, it needs to be attached to the sentence before it:
I have a lovely carved wooden box, which a friend brought me from India.
Several years ago, I met a woman who had traveled around the world.
Exercise One
In the following sentences, identify the fragments, and correct them either by attaching them to another sentence or by expanding them so that they make a complete thought. Two of the sentences are correct.
1. Alex went with Melissa to see the play. Although he was feeling ill and would rather have stayed home.
2. On the very edge of the cliff, where the ground fell away abruptly. A lone pine grew out from the sheer rock wall at a dizzying angle.
3. The glass teetered for a moment on the edge of the table. Then it fell.
4. The man was arrested very soon after the crime. Having left his fingerprints all over the crime scene before fleeing in the victim’s car.
5. Rob hurried past the group of protesters. Without even a glance at the signs that they were carrying.
6. The boy crept silently past the sleeping figures and had almost reached the outer perimeter of the encampment, undetected. When he suddenly sneezed
7. The first time that I went skiing. I fell and tore all the ligaments in my knee.
8. Even with all the work being done by so many different committees. It is unlikely that the project will be finished in time.
9. Because of budget cuts, we will have to downsize. We will try to minimize the number of positions to be eliminated.
10. Whenever you reach a decision. It is essential that you let me know immediately.