Compound & Complex Sentences

Learn how to connect ideas to make longer, more natural sentences.

Compound sentences — joining two equal ideas

A compound sentence joins two complete sentences with a coordinating conjunction. Both parts could stand alone.

Sentence 1 + and / but / so / or + Sentence 2

and

adds information

I like coffee and she likes tea.

but

shows contrast

I studied hard but I failed the exam.

shows result

It was raining, so we stayed inside.

shows alternative

You can take the bus or walk to school.

Complex sentences — a main clause + a subordinate clause

A complex sentence has a main clause (a complete idea) and a subordinate clause (an extra idea that depends on the main clause). They are joined by a subordinating conjunction.

Main clause + connector + Subordinate clause

— or —

Connector + Subordinate clause + , + Main clause

because

gives a reason

I left early because I was tired.

although

shows surprise / contrast

Although it was cold, we went out.

when

refers to a time

I felt nervous when I gave the presentation.

while

two things at the same time

She listened to music while she studied.

states a condition

If you practise every day, you will improve.

unless

except if / only if not

You won't pass unless you study.

📌 Comma rule: When the subordinate clause comes first, use a comma before the main clause.
Although it was cold, we went out. ✓ | We went out although it was cold. ✓ (no comma needed)

Compound vs Complex — what is the difference?

Compound

two equal, independent ideas

I was tired, so I went to bed.

Complex

one main idea + one dependent idea

I went to bed because I was tired.

💡 Tip: So and because are easy to confuse. So introduces the result. Because introduces the reason.
It was cold, so I wore a coat. (result) | I wore a coat because it was cold. (reason)

Exercise 1: Sentence Transformation

Rewrite each sentence using the connector given. Do not change the meaning.

Exercise 2: Error Identification

Each sentence contains one error. Click the wrong word, then select the reason why it is wrong.

Exercise 3: Error Correction

Each sentence has one wrong word. Click on it.

Exercise 4: Gap Fill

Choose the correct connector from the menu.

Exercise 5: Matching

Match each sentence beginning on the left with the correct ending on the right. Click a left item, then a right item.

Exercise 6: Sentence Sort

Drag each sentence into the correct category: Compound or Complex.

Exercise 7: Paragraph Gap Fill

Read each paragraph and choose the connector that best fits the meaning and flow of the whole text.

Your Scores

Complete the exercises to see your results here.