Complex Sentences: Subordinate and Relative Clauses

Q: How can you show contrast in a complex sentence without using the word "but"?

You can use subordinating conjunctions such as although , even though , or while .

Q: Which conjunctions are useful for explaining reasons or causes in Writing Task 2?

Use because , since , or as to connect an event with its cause.

Q: How should you structure sentences to discuss conditions or hypothetical situations?

Use conditional words such as if , unless , or provided that .

Q: When should you use "who" versus "which" in a relative clause?

Use who for people and which (or that ) for things and objects.

IELTS Academic · International English Language Testing System (IELTS) · 5 min read · Updated: Aug 12, 2026

Introduction: Why Complex Sentences are Your Secret Weapon

Hello! If you are aiming for a Band 6.0 or higher in IELTS, you need to master Complex Sentences. Many students think "complex" means "long and difficult," but that is not true. In the IELTS world, a complex sentence is simply a sentence that connects different ideas using special words like "because," "although," "which," or "if."

In the Writing and Speaking tests, the examiners look at your Grammatical Range and Accuracy. If you only use short, simple sentences, your score will likely stay below a Band 6. To get a high score, you must show that you can use a variety of sentence structures accurately. Don't worry if this seems tricky at first—by the end of these notes, you will have the tools to build these sentences yourself!

1. What Exactly is a Complex Sentence?

Think of a simple sentence like a single train carriage. It can move on its own (e.g., "The city is crowded."). A complex sentence is like a train with a main engine and a smaller carriage attached to it. The smaller carriage (the Subordinate Clause) cannot move alone—it needs the engine (the Main Clause) to make sense.

Example:
Simple: The city is crowded.
Complex: The city is crowded because many people move there for work.

2. Subordinate Clauses: Using Conjunctions

Subordinate clauses help you show the relationship between two ideas, such as cause, contrast, or condition. This is vital for IELTS Writing Task 2, where you must explain your arguments clearly.

A. Showing Contrast (The "But" Upgrade)

Instead of using "but" all the time, use although, even though, or while. This makes your writing look more academic.

Weak (Band 5): Technology is helpful but it can be distracting.
Improved (Band 7+): Although technology is helpful, it can be extremely distracting for students.

B. Showing Cause and Reason

Use because, since, or as to explain why something happens. This helps you meet the "Task Response" criteria by providing supporting details.

Weak (Band 5): People exercise more. They want to be healthy.
Improved (Band 7+): Many individuals exercise regularly since they want to maintain a healthy lifestyle.

C. Showing Condition

Use if, unless, or provided that. These are excellent for making predictions or discussing hypothetical situations in Speaking Part 3.

Example: If governments invest in green energy, pollution levels will likely drop.

Quick Review: When a sentence starts with Although, Because, If, or While, you must put a comma after the first clause.
Correct: Because the weather was bad, the flight was delayed.

3. Relative Clauses: Adding Detail with "Who" and "Which"

Relative clauses act like adjectives. They give more information about a person, place, or thing without starting a new sentence. This is the easiest way to improve your Grammatical Range.

A. Using "Who" for People

Weak: Doctors work long hours. They deserve high salaries.
Improved: Doctors who work long hours deserve to receive high salaries.

B. Using "Which" or "That" for Things

Weak: The system is very old. It needs to be replaced.
Improved: The system, which is very old, needs to be replaced.

C. Using "Where" for Places

Example: This is a problem in cities where the population is growing too fast.

Key Takeaway:

Relative clauses allow you to pack more information into a single sentence, which shows the examiner you have good control over English grammar.

4. How This Earns You Marks (The Examiner's Perspective)

In the official IELTS marking criteria for Grammatical Range and Accuracy:

Band 5: Uses mostly simple sentences. Attempts some complex sentences but makes many mistakes that can confuse the reader.
Band 6: Uses a mix of simple and complex sentence forms. You can make some mistakes, but the reader should still understand you.
Band 7: Uses a wide range of complex structures. Most sentences are error-free.

Did you know? You don't need every sentence to be complex. A good essay uses a mix. If every sentence is 40 words long, it becomes difficult to read!

5. Common Mistakes to Avoid

1. The "Fragment" Error: Writing a subordinate clause and stopping.
Wrong: Because the cost of living is rising. (This is an incomplete thought!)
Right: Because the cost of living is rising, people are saving less money.

2. Overusing "And": Using "and" to connect every idea makes you sound like a basic speaker.
Weak: I like the city and it has many shops and I go there often.
Improved: I frequently visit the city because it offers a wide variety of shops.

3. Punctuation with "Which": When using "which" to add extra information, always use a comma before it.
Example: The air quality, which has been declining for years, is now a major concern.

6. Useful Patterns for the Exam

Here are three patterns you can memorize and adapt for almost any Writing Task 2 essay:

Pattern 1 (The Contrast): While some people argue that [Idea A], I believe that [Idea B].
Pattern 2 (The Reason): This is a significant issue because [Reason], which leads to [Result].
Pattern 3 (The Condition): Unless the government takes action, the problem of [Topic] will continue to worsen.

Summary Checklist

Before you finish your practice test, ask yourself:
1. Did I use "although" or "while" to show two sides of an argument?
2. Did I use "which" or "who" to add detail to my nouns?
3. Did I use "if" or "unless" to talk about consequences?
4. Are my commas in the right place when I start a sentence with a connector?

Don't worry if this seems tricky at first! Start by trying to include just three complex sentences in your next practice essay. As you get more comfortable, you can increase the variety. Happy studying!

Quick check

Can you answer these now?

Open each question to check the key ideas from this chapter.

What is the definition of a complex sentence in the IELTS context?

A complex sentence is a sentence that connects different ideas using subordinating conjunctions or relative pronouns like "because," "although," or "which."

What are the two essential parts of a complex sentence?

The two parts are a Main Clause (which can stand alone as a sentence) and a Subordinate Clause (which relies on the main clause for its meaning).

How can you show contrast in a complex sentence without using the word "but"?

You can use subordinating conjunctions such as although, even though, or while.

Which conjunctions are useful for explaining reasons or causes in Writing Task 2?

Use because, since, or as to connect an event with its cause.

How should you structure sentences to discuss conditions or hypothetical situations?

Use conditional words such as if, unless, or provided that.

What is the punctuation rule for starting a sentence with a conjunction like "If" or "Because"?

When the subordinate clause comes first, you must place a comma after it to separate it from the main clause.

What is the main benefit of using relative clauses in IELTS writing?

Relative clauses allow you to add descriptive detail to nouns without having to start a new, simple sentence.

When should you use "who" versus "which" in a relative clause?

Use who for people and which (or that) for things and objects.

What level of grammatical complexity is required for a Band 7 score?

To achieve a Band 7, you must use a wide range of complex structures, and most of your sentences should be error-free.

What is a "sentence fragment" and how can you avoid it?

A fragment is an incomplete sentence that contains a subordinate clause but lacks a main clause.

Why is it a mistake to use "and" too frequently to connect ideas?

Overusing "and" makes you sound like a basic speaker and prevents you from demonstrating the grammatical variety needed for higher bands.

What punctuation is required when using "which" to provide extra information?

You should place a comma before the word "which" when adding non-essential, extra information to a sentence.

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