Complex Sentences

Independent clause + dependent clause working together

Master subordinators, clause relationships, and punctuation rules to create sophisticated, varied sentence structures. Includes interactive activities and a downloadable worksheet.

Lesson Objectives

Identify

Recognize complex sentences and their parts.

Build

Create complex sentences using subordinators.

Punctuate

Apply comma rules correctly.

Vary

Use different clause positions and relationships.

What is a Complex Sentence?

One independent clause + one (or more) dependent clauses

  • Independent clause: Can stand alone as a complete sentence
  • Dependent clause: Cannot stand alone; needs the main clause
  • Subordinator: Word that makes a clause dependent (because, although, when, if, etc.)
Example Because it was raining, we stayed inside.
Example She studied hard so that she could pass.

Pro Tip: Remove the subordinator. If the clause no longer makes sense alone, it's dependent!

Parts of a Complex Sentence

Independent Clause

• Has subject + predicate

• Complete thought

• Can stand alone

Example: "The dog barked"

Dependent Clause

• Has subject + predicate

• Incomplete thought

• Needs main clause

Example: "when the mailman arrived"

Subordinator

• Makes clause dependent

• Shows relationship

• Connects ideas

Examples: because, when, if, although

Note: The subordinator is the key! It transforms an independent clause into a dependent one.

Common Subordinators

Time

when, while, after, before, until, since, as soon as

"After the rain stopped, we went outside."

Reason/Cause

because, since, as

"Because I was tired, I went to bed early."

Contrast

although, though, even though, while, whereas

"Although it was expensive, we bought it."

Condition

if, unless, provided that, as long as

"If you study hard, you will succeed."

Place

where, wherever

"I'll go wherever you go."

Purpose

so that, in order that

"She saved money so that she could travel."

Memory Tip: Think about what relationship you want to show: time, reason, contrast, condition, place, or purpose.

Punctuation Rules

  • Dependent clause first: Use a comma after it
  • Independent clause first: Usually no comma
  • Exception: Use comma with contrast subordinators (although, though, even though)
DC first When I arrived, the meeting had started.
IC first The meeting had started when I arrived.
Contrast We enjoyed the movie, although it was long.

Pro Tip: If you can move the dependent clause to the front and it needs a comma there, it probably needs one at the end too (for contrast words).

Complex vs. Other Sentence Types

Simple The cat slept on the couch. (One independent clause)
Compound The cat slept, and the dog played. (Two independent clauses)
Complex The cat slept because it was tired. (IC + DC)
Compound-Complex When the cat slept, the dog played, and I read a book. (DC + IC + IC)

Quick Test: Look for subordinators. If you find one making a clause dependent, it's complex!

Building Complex Sentences

Step-by-step process

  1. Start with two simple sentences: "It rained." + "We stayed inside."
  2. Choose the relationship: Cause and effect
  3. Pick a subordinator: "because"
  4. Make one clause dependent: "Because it rained"
  5. Combine and punctuate: "Because it rained, we stayed inside."
Method 1 Because it rained, we stayed inside.
Method 2 We stayed inside because it rained.

Strategy: Always think about which idea is more important—that becomes your independent clause!

Creating Sentence Variety

Time After the concert ended, we walked to the car.
Condition If it rains tomorrow, the picnic will be cancelled.
Contrast Although the test was difficult, most students passed.
Reason She brought an umbrella because the forecast predicted rain.
Purpose We left early so that we could avoid traffic.
Place Wherever he goes, his dog follows.

Writing Tip: Use different subordinators to show different relationships and make your writing more interesting!

Common Mistakes

Fragment Error

WrongBecause I was tired.
FixBecause I was tired, I went to bed.

Missing Comma

WrongWhen it rains we stay inside.
FixWhen it rains, we stay inside.

Wrong Subordinator

UnclearWhile I like pizza, you prefer salad.
BetterAlthough I like pizza, you prefer salad.

Unnecessary Comma

WrongI study, because I want good grades.
FixI study because I want good grades.

Error Prevention: Always check that your dependent clause is attached to an independent clause!

Guided Practice

Combine "I was late" + "The traffic was heavy" → Because the traffic was heavy, I was late.
Fix Fragment "Although she studied hard" → Although she studied hard, she was nervous about the test.
Add Comma "When the movie ended we left" → When the movie ended, we left.
Choose Subordinator "___ it was raining, we went hiking" → Although it was raining, we went hiking.

Think about: What relationship am I showing? Time? Cause? Contrast? Condition?

Activity: Find the Subordinators

Click on the subordinators in each complex sentence.

Although the weather was cold , we enjoyed our hike .

She will succeed if she works hard .

When the bell rings , class will begin .

Hint: Subordinators are the words that make clauses dependent. Look for words like: because, when, if, although, since, after, before.

Activity: Comma or No Comma?

Choose whether each sentence needs a comma.

  • I'll call you when I arrive home.
  • When I arrive home I'll call you.
  • We went to the park although it was crowded.
  • Because she studied hard she passed the exam.

Remember: Dependent clause first = comma. Independent clause first = usually no comma (except contrast words).

Activity: Independent or Dependent?

Identify whether each clause is independent (IC) or dependent (DC).

  • when the movie ended
  • we went home
  • because it was late
  • she enjoys reading books
  • if you need help

Quick Test: Can it stand alone as a complete sentence? If yes, it's independent. If no, it's dependent.

Activity: Build a Complex Sentence

Combine the clauses with the appropriate subordinator and punctuation.

Choose Independent Clause:

Choose Subordinator:

Choose Dependent Clause:

Clause Order:

Your Sentence:

Select options above to build your sentence...

Remember: Dependent clause first needs a comma. Independent clause first usually doesn't (except for contrast).

Activity: Fix the Fragments

Complete these sentence fragments by adding an independent clause.

Because it was raining heavily
When the teacher entered the classroom
Although she was very tired
If you finish your homework early

Tip: Your independent clause should have a subject and predicate and make complete sense with the dependent clause.

Practice: Multiple Choice

Question:

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Strategy: Look for subordinators to identify complex sentences. Check punctuation based on clause order.

Score: 0

More Practice

Additional practice to strengthen your skills.

Question:

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Score: 0

Real World Applications

Academic Writing

"Although many studies have been conducted, researchers still debate the causes of climate change."

Use: Show relationships between ideas clearly.

Business Communication

"When the project is completed, we will evaluate the results and plan the next phase."

Use: Express conditions and timelines professionally.

Creative Writing

"As the sun set behind the mountains, the village settled into peaceful silence."

Use: Create flowing, sophisticated prose.

Daily Conversation

"If you're free this weekend, we could go to the beach."

Use: Express conditions and make suggestions.

Pro Tip: Complex sentences help you sound more sophisticated and express nuanced relationships between ideas.

Writing Tips with Complex Sentences

  • Vary your sentence structure: Mix simple, compound, and complex sentences
  • Show clear relationships: Use subordinators that match your intended meaning
  • Avoid overcomplicating: Don't chain too many dependent clauses together
  • Read aloud: Complex sentences should flow naturally when spoken
  • Practice transitions: Use complex sentences to bridge ideas between paragraphs
Good Mix The weather was perfect. When we arrived at the beach, we set up our umbrellas. The water was warm, so we went swimming immediately.
Too Complex When we arrived at the beach, which was crowded because it was a holiday, we set up our umbrellas while other families were looking for spots.

Balance Tip: Aim for clarity first, sophistication second. Your reader should understand your meaning easily.

Quick Review

Complex Sentence Independent clause + dependent clause (with subordinator)
Comma Rule Dependent first = comma; Independent first = usually no comma
Subordinators because, when, if, although, since, after, before, while, unless...
Purpose Show relationships: time, cause, contrast, condition, place, purpose

Remember: Every subordinator has a job—it shows how two ideas relate to each other!

Assessment

Instructions: Choose the best answer for each question, then click Check Answers.

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Download Worksheet

Assessment Tip: Look for subordinators to identify complex sentences. Check that dependent clauses are properly connected.

Key Takeaways

Complex sentences combine independent and dependent clauses.
Subordinators show relationships between ideas.
Comma after dependent clause when it comes first.
Use variety to make writing more sophisticated.
Avoid fragments—dependent clauses need independent clauses.
Choose subordinators that match your intended meaning.

Master's Checklist: (1) One IC + one DC? (2) Correct subordinator? (3) Proper comma placement? (4) Clear meaning?

Next Steps

Continue Your Learning Journey

  • Practice Daily: Write 5 complex sentences with different subordinators
  • Read Actively: Identify complex sentences in books and articles
  • Edit Your Writing: Convert some simple sentences to complex ones
  • Learn More: Study compound-complex sentences next
  • Apply Skills: Use complex sentences in your essays and reports

Download the worksheet to practice offline!

Excellent Work!

You completed the Complex Sentences lesson

You now understand how to create sophisticated sentence structures!

What's Next?

  • Practice with the downloadable worksheet
  • Apply complex sentences in your writing
  • Explore compound-complex sentences
  • Share your knowledge with others

Remember: Great writing uses a variety of sentence types. Complex sentences are your tool for showing sophisticated relationships between ideas!