IELTS Writing- How To Write a Complex Sentence

How to write a complex sentence IELTS


One of the biggest mistakes students make in IELTS writing is to try and show off and be overly ambitious with their grammar. This is because many students think that all of their sentences need to be ‘complex’ (they don’t!) and them not understanding what a ‘complex’ sentence is. Trying to write overly complicated sentences leads to grammar mistakes and this will lead to lost marks in many different areas.

This post will look at:

• how many ‘complex’ sentences you actually need in each paragraph
• what a ‘complex’ sentence actually is
• how to make complex sentences
• examples to help us understand and transfer this knowledge to our own writing

What does the examiner expect?

If we look at the examiners’ marking scheme it states that in order to get a band 6 for grammar we need to:

• use a mix of simple and complex sentences.

For band 7 it states:

• Use a variety of complex structures.

This obviously means that we should use complex sentences in our writing, but it does not mean that we should try to make all of our sentences complex. All band 9 answers that I have seen use a mixture of both simple and complex sentences. The key is to know when to use them and we will look at this below. But first, we need to understand what a complex sentence actually is.

What is a complex sentence?

The main problem here seems to be the word ‘complex’. Complex, in this situation, does not mean complicated, long or impressive. This is a common misconception and leads to students writing very long and grammatically incorrect sentences that are very difficult to understand.

For example:

‘In the modern world, global warming is one of the most popular topics causing many environmental difficulties and tough challenges arising from its serious consequences.’

This is a very typical sentence from an essay that is trying to be overly complex. This student has tried to put four simple ideas in to one paragraph and the result is an awkward and incoherent sentence. They have lost control of the grammar and this affects the meaning. When meaning is affected it stops the reading understanding what is being said and that is really bad for you IELTS writing band scores.

‘Complex’ sentences are not actually very complex; they are just simple two or more simple sentences put together. Putting them together makes the essay more coherent and cohesive.

Let’s look at the first example again. In the sentence above there are four simple ideas that we can put in to simple sentences:

1. Global warming is a common topic these days.
2. Global warming causes environmental problems.
3. There are tough challenges associated with global warming.
4. Global warming has very serious consequences.

If we write all of our sentences in the IELTS exam like this we lose marks because they are too simple. What we need to do is put them together to make complex sentences.

Complex Sentence Examples

For example:

One of the most common environmental issues is global warming which causes many serious environmental problems. There are tough challenges associated with this issue and its effects have very serious consequences.

I don’t think there is anything ‘complex’ about these sentences, just simple ideas, simply put together.

‘Complex’ is just a label, not a description.

What I have done is take each of the four simple sentences and put them together in two complex sentences. This result is a grammatically correct, easy to understand paragraph.

When should I use complex sentences?

In general, we should use simple sentences when making main points; normally at the beginning of a paragraph. We should then use complex sentences when expanding on the main point, for instance when giving a supporting example or explaining your main point.


This is a question about whether ‘fast food’ or ‘junk food’ should be taxed at a higher rate than normal food.

‘Increasing taxes would raise prices and lower consumption. Fast food companies would pass on these taxes to consumers in the form of higher prices and this would lead to people not being able to afford junk food. For instance, the cost of organic food has proven prohibitively expensive for most people. Despite this, people in many developed countries, where the problem is most acute, can afford price hikes and will continue to eat high fat meals.’

The first sentence is the ‘topic sentence’ and makes the main point. It is therefore acceptable for this to be a simple sentence.

The second sentence explains the main point and uses the word ‘and’ to link two simple sentences together, to make one complex sentence.

The third sentence gives an example and uses the linking phrase ‘for instance’. The final sentence makes a concession (shows the limitation of the argument) and is also a complex sentence, linking more than one idea together.

This paragraph has a mix of simple and complex sentences and therefore satisfies the marking criteria.

How do I make a complex sentence?

Remember that a complex sentence is just more than one simple sentence put together to make one sentence. We therefore need to learn and become confident using the various grammatical structures that allow us to do that. Below are a few ways we can link ideas together in a sentence.

To make a complex sentence we normally should have two things- a dependent clause and an independent clause. A clause is a group of words with both a subject and a verb.

An example of a dependent clauses is ‘….because the weather was cold.’ This is a dependent clause because it has a subject and a verb but it doesn’t make any sense on its own. To make sense we need to add an independent clause.

As the name suggests, an independent clause can make sense on its own. For example, ‘I wore a warm coat.’ If we combine these two clauses we get a complex sentence- ‘I wore a warm coat because the weather was cold.’

As you can see, ‘complex’ sentences don’t have to be complicated. Let’s now look at other ways we can make complex sentences.

1. Relative Clauses

You can use relative clauses to give essential or extra information about a person, place, or thing. This makes our writing more fluent and more coherent. We do this by using relative pronouns like who, which and that. For example, ‘He’s the kind of person who is always friendly.’

For example:

Air pollution can cause health problems. Air pollution is largely caused by motor vehicles.

We can convert these two simple sentences in to one complex sentences by using the word ‘which’.

Air pollution, which is mostly caused by motor vehicles, can cause health problems.

For example:

There is evidence that some people are more likely to smoke. These people have parents and friends who smoke.

We can link both of these sentences together by using the word ‘that’.

There is evidence that people who have parents and friends that smoke are more likely to smoke.

2. Subordinate Clauses

A subordinate clause can describe nouns and pronouns; describe verbs, adverbs, and adjectives; or act as the subject or object of another clause. They are made by connecting an independent clause with a dependent clause with words like as, because, while, until, even though, although, when and if.

3. Conditional Clauses

Also known as ‘If clauses’, they are used to express that the action in the main clause can only take place if a certain condition is met.

For example:

If I had a million dollars, I would quit my job.

I will be really happy, if I pass the IELTS test.

These clauses are good for giving examples in IELTS writing part 2.

For example:

‘Increasing taxes would raise prices and lower consumption. Fast food companies would pass on these taxes to consumers in the form of higher prices and this would lead to people not being able to afford junk food. If the cost of organic food proves prohibitively expensive for most people, they will simply not buy it. Despite this, people in many developed countries, where the problem is most acute, can afford price hikes and will continue to eat high fat meals.’

They are also useful for talking about unreal situations or to speculate about results in the past or present.

There are four different kinds of conditionals which I will outline below:

Zero Conditionals are used to talk about information that is true or facts. We can use if or when to introduce the conditional.

Example: Nowadays when we travel long distances, we usually use air travel.

First conditionals are used to talk about things in the present or future.

Example: If the city’s population continues to grow, we will need to build more infrastructure.

Second Conditionals are used to talk about things that are impossible.

Example: If the sun didn’t come up tomorrow, we wouldn’t have any life on earth.

Third Conditionals are used to speculate about past events. It is often used when we regret something or to imagine a past unreal situation.

Example: The Second World War would have never happened, if Germany had been given a fairer peace settlement in Word War One.

4. Compound Sentences

Compound sentences consist of two independent clauses linked together with a conjunction such as ‘and’, ‘for’ or ‘but’.


I really want to study, but I’m too tired.
She got to the test centre early, and she did really well on her IELTS test.

Some students think these sentences are too simple to count as complex but they are wrong.


The crucial thing is to understand and be able to use these grammar structures before your IELTS test. Some students memorise lots of structures and try to insert them in to their essays without giving much thought to how they work or if they are accurate. This will only lead to unnatural and incoherent sentences. Remember that your sentences need to be also error free so only use structures you are confident using.

They key is to only use them appropriately. Concentrate on answering the question and if you know how to use these structures they will flow naturally.

Next Steps

I hope this post has demonstrated that you can write your ideas down in a clear and simple way and still satisfy the marking criteria for complex sentences.

When you are practicing IELTS writing questions try to think of what you want to say in simple sentences and then think of how these might be linked in to complex sentences. After enough practice it will become a natural thing to do and your writing will really improve.

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  1. Khalidah says

    Amazing explanation. Thank you ^^

  2. Tien says

    Dear teacher,

    Thank you for your useful lesson. Can I have the following question about it? I actually dont understand why you use “would” in this sentence “Fast food companies would pass on these taxes to consumers in the form of higher prices and this would lead to people not being able to afford junk food” instead of “Will”. Thank you so much!


  3. Taovyc says

    this is an excellent post,i look forward to your contribution on speaking too

    1. Maisa says

      Yes. that is absolutely right I strongly agree with. Due to the purpose of writing is to show the examiner that the candidate can write smoothly and give the idea correctly, even though, in simple words or simple grammar. Not use complex sentences overly more and more, in person I think that.

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