A complex sentence is made up of an independent clause and a subordinate clause. Here are some subordinate clause words that can begin a complex sentence: after, before, because, if, since, unless, when, while
Anytime you begin a sentence with one of these words, you are writing a subordinate clause. You have to put a comma after the clause and then finish the sentence with an independent clause.
Think of a thought that begins with the word after.
After I eat breakfast
After I get done with my homework
After the guests leave
Each one of these thoughts is a subordinate clause – and a fragment – unless you add a comma and some more information.
After I eat breakfast, I will do the laundry.
After I get done with my homework, I will take a shower.
After the guests leave, I will go to bed.
When a sentence begins with a subordinate clause word, you must add a comma and more information to make a complete sentence.
▶ Now you try it. Use one of these subordinate clause words – if, until, or when – to begin a sentence. After you have written the subordinate clause, add a comma and then finish the sentence with an independent clause. How did you do? Did you make a complete complex sentence? Good for you!