When completing a sentence or choosing from several sentences to select the most effective one, you must beware of two common writing errors: run-ons and sentence fragments. If you are familiar with what an incorrect sentence sounds like, it will set off alarms for you, and you will be able to quickly move on to find the right one.
When a sentence consists of more than one clause (a group of words that contains a subject and a verb), those clauses must be joined properly. It is never acceptable to hook two clauses together with a comma, as the “sentence” below does. That’s called a run-on sentence.
Wrong: Nietzsche moved to Basel in 1869, he planned to teach classical philology.
There are a number of acceptable ways to fix a run-on.
Correct: Nietzsche moved to Basel in 1869. He planned to teach classical philology.
Also correct: Nietzsche planned to teach classical philology; therefore, he moved to Basel in 1869.
Also correct: Nietzsche moved to Basel in 1869, and he planned to teach classical philology. (The words and, or, for, but, nor, so, and yet are called coordinating conjunctions.)
Also correct: Because Nietzsche planned to teach classical philology, he moved to Basel in 1869. (The words because, although, if, though, etc. are called subordinating conjunctions.)
Also correct: Nietzsche, who planned to teach classical philology, moved to Basel in 1869. (The words who, which, where, whom, that, and whose are called relative pronouns.)
Sentence fragments are usually pretty easy to spot. When you read one, your reaction is usually, “Huh?” There is something crucial missing. In more technical terms, a sentence fragment is a group of words that looks like a sentence, but it is either grammatically or logically incomplete. Here is the grammatical test: to be a sentence, the group of words has to contain both a subject and a verb related to one another.
Take a look at this example:
The man in the lineup wearing the plaid shirt.
Well, you have a subject—"the man." And you seem to have a verb—"wearing." But "wearing the plaid shirt" really just modifies the subject, giving us more details about the man. There is no verb. What about the man in the lineup? Did he do something? Or did someone do something to him? What was going on? Who knows?
You can complete the sentence by adding a verb:
The man in the lineup wearing the plaid shirt mumbled so much the witness couldn’t understand him.
The man in the lineup wearing the plaid shirt was the witness’s first choice.
But some sentence fragments do have a subject and verb; these are sentences that are logically incomplete. Look at this:
When the sergeant has to fill out a lot of paperwork.
There is the subject, "the sergeant." And there is a verb attached—"has to fill out a lot of paperwork." But what about that word "when" at the beginning of the sentence? That leads us to expect information that just isn’t there. Here’s how that fragment can be turned into a full sentence:
When the sergeant has to fill out a lot of paperwork, he gets very cranky.
The sentence may also be corrected by deleting "when":
The sergeant has to fill out a lot of paperwork.