English Learning Box


The Complex Sentences Exercise

Before doing the exercise, let’s review the complex sentences.

Grammar Rules


  • Definition: A complex sentence is a sentence that contains one independent clause (a complete thought that can stand on its own) and at least one dependent clause (a phrase that cannot stand on its own as a sentence because it doesn’t give a complete thought).
  • Purpose: Complex sentences show relationships between ideas, such as cause and effect, time, contrast, or conditions.
  • Structure: The independent clause ( or main clause) is the main part of the sentence, while the dependent clause (or subordinate clause) provides additional information or modifies the main clause.
  • Connecting Words: Subordinating conjunctions are used to connect the dependent clause to the independent clause. Common subordinating conjunctions include:
    • although, even though, though, as, because, since, before, after, so that, if, unless, until, till, when, whenever, where, wherever, while, once, by the time, as soon as

(Check compound sentences and coordinating conjunctions here.)


  1. Cause and Effect:
    • I stayed home because I was sick. (Independent clause: I stayed home; Dependent clause: because I was sick)
    • Since it was raining, we canceled the picnic. (Dependent clause: Since it was raining; Independent clause: we canceled the picnic)
  2. Time:
    • We’ll meet you when the movie ends. (Dependent clause: when the movie ends; Independent clause: We’ll meet you)
    • I’ll call you before I leave. (Independent clause: I’ll call you; Dependent clause: before I leave)
  3. Contrast:
    • Although she was tired, she finished her work. (Dependent clause: Although she was tired; Independent clause: she finished her work)
    • Even though I studied hard, I didn’t pass the test. (Dependent clause: Even though I studied hard; Independent clause: I didn’t pass the test)
  4. Conditions:
    • If you finish your homework, you can watch TV. (Dependent clause: If you finish your homework; Independent clause: you can watch TV)
    • Unless you apologize, I won’t forgive you. (Dependent clause: Unless you apologize; Independent clause: I won’t forgive you)


  • We can write more than one dependent clause to make a complex sentence.
  • We can switch the order of the clauses without changing the meaning of the sentence, but the punctuation may need to be adjusted. If the sentence starts with the dependent clause, we separate it with a comma. But if the independent clause comes first, we do not need a comma.

When I arrive home, I will tell you what happened.

I will tell you what happened when I arrive home.

  • Complex sentences can be combined with compound sentences to create even more complex structures (often referred to as compound-complex sentences).

Although she was sick, she continued working, for she had to submit the project the next day.

Time to practice!
Connect each pair of simple sentences to make a complex sentence using the subordinating conjunctions provided. Remember to use a comma after the subordinating (dependent) clause if it comes at the beginning of the sentence.
1. We visited London. We visited the Clock Towers. (when)

2. He had opened the gift. He realized it wasn't sent to him. (before)

3. You finish your homework. You can play video games. (if)

4. They didn't like each other. They had to work together. (although)

5. I stayed at college till 8 p.m. I wanted to finish my biology project. (because)

6. He fell down. He was fixing the light bulb. (while)

7. She won't decide on what to study. She gets the exam results. (until)

8. The guests had already left. I arrived home. (by the time)

9. I will eat. I make an urgent phone call. (after)

10. She was sick. She applied for a day off from work. (since)

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