A sentence must contain three things:
- A subject
- A verb
- A complete thought
A sentence fragment is missing at least one of these things. We speak in sentence fragments all the time; you would probably get a lot of strange looks if you only spoke in complete sentences. However, you should avoid writing sentence fragments if you want your message understood (except in very rare instances).
How can you tell if it’s a sentence fragment?
The best test is to read your sentence aloud. Does it sound right? If you walked up to a group of strangers and read your sentence, would it make sense to them, or would they be waiting for you to finish? Your sentence may make sense to you because you are the person who wrote it, but consider it from the perspective of someone else. Does your sentence have a clear subject, verb and thought?
Missing Subjects
Fragment: Bought milk at the store.
Who bought milk at the store? You? Some guy? Without a subject, this is not a complete thought and makes no sense. Add a subject, however, and you have a complete thought and complete sentence.
Complete: The breakfast cereal aficionado bought milk at the store.
Missing Verbs
Fragment: The yeti’s fur shining in the sun.
What about the yeti’s fur? What is it doing? Why does it matter? To turn this descriptive fragment into a sentence, you must add a verb and make the fragment a complete thought.
Complete: The yeti’s fur shining in the sun temporarily distracted me from its huge claws.
Incomplete Thoughts
Fragment: Until he mastered juggling cats.
The word until makes this a fragment. Until what or when? You can fix this fragment by adding an independent clause to finish the thought.
Complete: Until he mastered juggling cats, Percival was sure he would fluck this semester of Clown College.
Exceptions to the Rule: Commands or Requests
Consider the following sentences:
Turn in your assignment at the end of class.
and
Please take that diaper off his head.
These seem like sentence fragments——there is no clear subject in either sentence. However, commands and requests have an unstated subject: you. So, you interpret the sentences as:
(You) turn in your assignment at the end of class.
and
(You) please take that diaper off his head.
Run-on Sentences and Comma Splices
A run-on sentence occurs when two independent clauses are joined without the correct punctuation or conjunction. Run-on sentences come in two varieties:
- When a writer fails to include punctuation and a coordinating conjunction between two independent clauses
- When a writer creates a comma splice——two or more independent clauses joined with just a comma and no coordinating conjunction
Here is example of a run-on sentence:
A liger is a lion and a tiger mixed it is bred for its use in magic.
Join the independent clauses with a comma and coordinating conjunction (FANBOYS: for, and, nor, but, yet, so):
A liger is a lion and a tiger mixed, and it is bred for its use in magic.
Join the independent clauses with a semicolon:
A liger is a lion and a tiger mixed; it is bred for its use in magic.
Rewrite one of the clauses to make it a dependent clause and separate them with a comma:
Because a liger is a lion and a tiger mixed, it is bred for its use in magic.
Size Doesn’t Matter
A run-on sentence is not defined by its length! Short sentences can be run-on sentences, too. Consider the following sentence: He laughed she smiled. Even though the sentence only has four words, it is still a run-on sentence. Lack of correct punctuation and coordinating conjunctions, not length, are what define a run-on sentence.
Comma splices are a type of run-on sentence that occurs when two independent clauses are incorrectly joined with just a comma. To correctly join two independent clauses, you need a semicolon (;) or a comma and coordinating conjunction.
Here is an example of a comma splice:
Unicorns are great pets, you can roast marshmallows on their horns.
Here is the correct version with a semicolon:
Unicorns are great pets; you can roast marshmallows on their horns.
Here is the correct version with a comma and coordinating conjunction:
Unicorns are great pets, for you can roast marshmallows on their horns.
Grammaphile 