There are four main problems that prevent people from writing complete, grammatically correct sentences. These problems include: (a) the sentence fragment; (b) the run-on sentence; (c) lack of subject-verb and pronoun-reference agreement; and (d) lack of parallel structure.
Sentence Fragments
A fragment is a sentence which is not complete, and therefore not grammatically correct. Sentence fragments are problematic because they are disjointed and confusing to the reader. There are three main causes of fragments: (a) a missing subject; (b) a missing verb; (c) "danger" words which are not finished.
There are three ways to check for sentence completeness:
1. Find the subject. A subject is the noun or pronoun about which something is written. To find the subject of a sentence, identify who or what is doing the action. If there is no subject, the sentence is a fragment. Consider the two examples below.
"The student felt nervous before the speech."
"Thought about leaving the room."
The first sentence above is complete, because it contains both a subject and a verb. The subject of this sentence is the student. The sentence contains a subject which answers the question, "who or what felt nervous?" The second sentence is a fragment, because there is no identifiable subject. The sentence does not contain a subject which answers the question, "who or what thought about leaving?" To correct the second sentence, one could write: "He thought about leaving the room." Alternatively, one could combine the two sentences to form one complete sentence: "The student felt nervous before the speech, and thought about leaving the room."
2. Find the verb. A verb is the action word in a sentence. Verbs express action, existence or occurrence. To find the verb in a sentence, identify what happened. If there is no identifiable action, the sentence is a fragment. Consider the two examples below.
"Many scientists, such as Einstein, think in strange ways."
"Many scientists think in strange ways. Einstein, for example."This first example above has one complete sentence followed by a fragment. "Einstein, for example" is a fragment because there is no verb. "Einstein" serves as the subject (he is the one doing something), but the rest of the sentence does not express what action he is taking. The second example is a complete sentence. In this case, the sentence contains both a subject (scientists) and a verb (think). Alternatively, one could write the following: "Many scientists think in strange ways. Einstein, for example, could not tolerate more than one bar of soap in his home." In this case, there are two complete sentences. In the second sentence, the subject is Einstein and the verb is "could not tolerate."
3. Check for "danger" words. A danger word is one which introduces a thought that requires a follow-up phrase. Such words are sometimes called "cliff-hangers" because they begin a statement, but leave it "hanging" without a finish. Consider the phrases below.
"If you come home..."
"When the rain falls..."
"Because he is mean..."
The danger words in the sentences above are "if," "when" and "because." When these words are used at the beginning of a phrase, they require a follow-up phrase to conclude the thought.
Example: If you come home on time...then what?
Correct:If you come home on time, I will buy you a present.
Example: When it rains...what happens?
Correct:When it rains, the gutters become clogged.
Example: Because he is mean...what is the result?
Correct:Because he is mean, I will not take a class from him.
Danger words are helpful when writing sentences, but one must be sure to include a concluding phrase when these words are used.
Commonly used danger words include: after, unless, although, how, as if, when, because, where, before, while, if, until, once, so that, since, whether.
