Changing Compound Sentences to Complex Sentences

Here's an example of a compound sentence and a complex sentence.

What makes this sentence compound?

Well, it's made up of two independent clauses, each with a subject and a verb, joined together by the coordinating conjunction "but." Think of compound sentences as being two or more simple sentences joined together.

What makes this sentence complex?

Here, it has an independent clause, and here it has a dependent clause—that is, one that doesn't make sense on its own. The subordinating conjunction "unless" has been used to join these clauses.

Let's have a go at changing the compound sentence to a complex sentence.

We'll have to replace the coordinating conjunction with a subordinating conjunction, and in doing so, change one of the independent clauses to a dependent clause.

Here are some subordinating conjunctions we could use to help. Let's separate our two independent clauses:

• Rick has a test today.
• He hasn't studied.

Here are some dependent clauses we could join to each clause:

• Although he looks relaxed
• If the schedule is correct
• As he had a busy weekend
• Since he already knows the content

Here are some complex sentences we could create:

• Although he looks relaxed, Rick has a test today.
• Rick has a test today if the schedule is correct.
• Rick hasn't studied as he had a busy weekend.
• Since Rick already knows the content, he hasn't studied.

Here are the independent clauses, and here are the dependent clauses. And here are the subordinating conjunctions.

Notice that if the dependent clause begins the sentence, as it does in these two examples, we must add a comma between the clauses. Now, we need to be careful—just because we use one of these words doesn’t mean we will have created a complex sentence.

Take these sentences, for example:

• Because of the weather, they stayed indoors.
• It has been raining since last Friday.

Even though the words "because" and "since" have been used, they have not been used to form a dependent clause. Remember, a clause must have a subject and a verb.

Let's see how we could turn these into complex sentences:

• Because they were cold, they stayed indoors.

Here, we have added a subject and a verb, so now we have a dependent clause to go with our independent clause.

• It has been raining since Paul arrived last Friday.

By adding a subject and a verb, we have created a dependent clause to go along with our independent clause.

Have a go at changing the following compound sentences into complex sentences.

Use this list of subordinating conjunctions to help you, but remember, there are many more. Share your sentences in the comments below. Hope to see you soon for our next lesson.