Complex Sentences

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A complex sentence is a sentence that is formed by joining an independent clause with a dependent clause. An independent clause is a simple sentence and contains a subject, a verb, and expresses a complete thought.

A dependent clause is a clause that has a subject and a verb, but, by itself, does not express a complete thought. Dependent clauses are also called subordinate clauses because they are sub sentences or something less than sentences.

In a complex sentence, the dependent clause always begins with a subordinating conjunction. There are many words in the English language that function as subordinating conjunctions; the table below contains only a partial list.

Subordinating conjunctions used to indicate when
after, before, until (till)1, when, while
I couldn't go home until I met my friend downtown.
Subordinating conjunctions used to indicate a cause or result.
as, because, since, whereas
Since it was raining, we had to cancel the picnic.
Subordinating conjunctions used to indicate a condition or exception.
even though, although, if, though, unless
If you come with me, I'll treat you to dinner.

Caution: Many writers create sentence fragments by writing dependent clauses without a corresponding independent clause. In the following examples, notice the subordinating conjunction at the beginning of the clause.

    1. Since it was almost time to go home.
    2. Even though I had just gotten home.
    3. Before I go on vacation.

Each of the fragments above can be corrected by adding an independent clause. The independent clause can be added to either the beginning of the sentence fragment or the end. For example,

    1. Since it was almost time to go home, I got our coats from the closet.
      I got our coats from the closet since it was almost time to go home.


    2. Even though I had just gotten home, I had to go back to the office for another meeting.
      I had to go back to the office for another meeting even though I had just gotten home.


    3. Before I go on vacation, I have to finish this project.
      I have to finish this project before I go on vacation.

Note: When the subordinate clause begins the sentence a comma is needed after the dependent clause. When the independent clause begins the sentence no comma is needed.

Practice

Identify the subordinating conjunction and the dependent clause in the following complex sentences. Click the sentence to see the correct answer.

    1. You have to practice every day if you want to improve.
    2. When you are ready to go, call me.
    3. The children started playing again as soon as Margaret went to sleep.
    4. Although it was almost time to go home, we stopped to take one last look around.
    5. You can't go out and play until you finish your homework.


1Till is a shortened form of until and is used more often in spoken English than in written English. Till may be used in informal writing but should not be used in formal writing.