Sentence structure is the order and arrangement of the clauses in a sentence, which is a group of words that express a complete thought. Three of the most common types of sentence structure are simple, compound, and complex sentences. Each of these can be identified by the number and types of clauses found within them.
Types of Clauses
The term "clause" simply refers to a group of words that form an idea, somewhat synonymous with "sentence." An "independent clause" is a phrase that includes a subject and predicate and can stand on its own as a full statement. In contrast to this, a "dependent clause" might have both a subject and predicate but what it expresses is incomplete. This distinction is important, as various types of sentence structure are created by combining these two forms.
Subject-Predicate Structure
Many times, but not always, sentences start with a subject. This subject is commonly a noun or noun phrase. In the clause, "Matt washed the dishes," the subject is "Matt." The predicate normally comes at the end in sentence structure and is usually comprised of the verb and its modifiers. In the example above, "washed the dishes" is the predicate; "washed" is the verb or action and "the dishes" is the direct object, which identifies what the subject acts upon.
Simple
A simple sentence structure consists of one independent clause. The previous example is simple and expresses a complete idea. While it is a short example, sentence length cannot be used to judge its type. "The man walked down the street to see if the newspaper had arrived at his favorite corner store," is simple, with only a single independent clause, though it is much longer than the previous example.
Compound
Compound sentences consist of two or more simple or independent clauses, joined by a coordinating conjunction such as "and" or a coordinating adjective like "however." "I walked to the store," and "The clerk waved hello," are both simple sentences. They can be joined together to create the compound, "I walked to the store, and the clerk waved hello."
Complex
A complex sentence has one independent clause joined together with a dependent clause. Since dependent clauses do not express complete ideas, they often become subordinate clauses that do not have as much strength as independent ones. For example, "Both gold and coal are valuable, although gold is worth more," consists of the independent clause "Both gold and coal are valuable" and the dependent clause, "although gold is worth more." This dependent clause does not express a full idea, and it is a subordinate because the conjunction "although" indicates that what follows it is less important than the other clause.
Compound-Complex
The combination of the compound and complex forms create a sentence structure known as "compound-complex." This occurs when a simple and complex sentence are combined together, or two complex types become connected. For example, "I walked to the store, and I bought some milk, though I really wanted ice cream," is compound-complex. It begins with a simple sentence, "I walked to the store," which is connected by "and" to a complex sentence consisting of the independent clause "I bought some milk," and the dependent clause, "though I really wanted ice cream."
Fragments and Imperatives
When dealing with sentence structure, it is important to avoid fragments. A fragment is an incomplete thought or a dependent clause by itself. "However, I went to the store," is a fragment, since there is clearly something missing from the idea expressed by it. It contains a subject and predicate, but the conjunction "however," indicates a missing element.
Fragments should not be confused with "imperatives," which give commands. The subject of an imperative statement is the understood or implied "you." "Come here" is an example of such a command, understood as "You, come here." Many people distinguish a fragment from an imperative by adding the word "you" before it and seeing if it makes sense.