How to use Complex Sentences in IELTS writing?

The word “complex” might sound scary these days as everything “simple” is being promoted as the better alternative. But complexity can be simplified too! In fact, “complex” is nothing but a few “simples” joined together in different ways to serve a purpose. If you can manage complexity, you will be able to showcase your skills, which is very important in the IELTS writing test.

According to the IELTS marking scheme or band descriptors, you need to use a mix of simple and complex sentences in your writing test to get a band 6. If you are aiming for band 7, then you should use a variety of complex sentences. The higher the band you want to earn, the more complex sentences you should use. The reason is the grammatical range that you should reveal in your writing. You should however be aware that the expanded grammatical range must have accuracy too; otherwise, you will lose marks! Punctuation is also important to deliver clear meaning.

Complex sentences are not complicated. They are just more informative and cohesive and can prove your proficiency and depth of knowledge. They also make your writing more interesting and easier to read.

This article will help you master the art of writing complex sentences in IELTS writing. By the time you finish reading it, you know how to write complex sentences effortlessly to get higher band scores.

What are complex sentences?

Complex sentences are created by joining 2 or 3 simple sentences to expand the main idea or to explain it. They can also link more than one idea together.

Depending on the purpose of writing a complex sentence, the “simples” might be dependent or independent.

As the name implies, an independent sentence has its own meaning, but a dependent one is meaningless without the independent. Its purpose is to provide a fact about the independent sentence.

Complex sentences are a critical part of your grammar which accounts for 25% of your writing mark. They expand the range of your grammar, assuming you write them accurately!

How to write complex sentences?

There are many ways to write complex sentences, but we explain the four most common types to make it absolutely simple for you:

1.    Compound sentences

Use simple conjunctions such as “and, but, so and yet” to join two main ideas presented in two independent sentences.


  • Smoking causes lung diseases, yet some people smoke cigarettes.
  • The temperatures are rising everywhere, so air conditioners are increasing energy bills.
  • Plastic pollution is affecting the oceans’ ecosystem, but humanity doesn’t take serious action about it.

As you can see, each simple sentence is meaningful on its own, and when joined together, they represent two related facts.

2.    Relative sentences

Use relative pronouns such as “who, which and that” to elaborate on the main sentence. The relative might be dependent on the main sentence.


  • Air pollution is a huge global issue that causes many deaths every year.
  • Air pollution, which causes many deaths every year, is a huge global problem.
  • The mass graves found recently in Canada belong to children who were indigenous.

As you can see in the second example, sometimes a relative pronoun can come first to emphasize the more important fact.

3. Subordinate sentences

Use subordinate conjunctions such as “because, while, when, as, until, although, even though, if, unless and whereas” to describe some facts about the main sentence. The subordinate is dependent on the main sentence.


  • COVID pandemic is still raging throughout the world because the virus keeps mutating.
  • United States is relaxing COVID restrictions after vaccination, whereas many other countries are still struggling.
  • As I expected from the artist, the exhibition at the gallery was remarkable!

As you can see in the last example, the two sentences should be separated with a comma when the subordinate conjunction comes at the beginning of the complex sentence.

4. Conditional sentences

Use the “if…then” structure to express the condition in which the main clause would be true.

There are three types of conditional sentences that differ in their verb tenses:

Type 1: has “simple present tense” in the if-clause and “simple future tense” in the main clause.

Type 2: has “simple past tense” in the if-clause and “present conditional or present continuous conditional tense” in the main clause.

Type 3: has “past perfect tense” in the if-clause and “perfect conditional tense” in the main clause.


  • If solar power becomes the primary source of energy in more countries, then air pollution will be solved.
  • Globalization wouldn’t be a reality now if we held on to the racism of the past.
  • If they had taken the warnings seriously, the surfside condo would not have collapsed!

As you can see, sometimes the “if clause” comes after the main one, which makes the use of a comma unnecessary. “Then” can also be omitted because the conditionality of the statement is obvious. In this case, a comma should separate the two sentences.


You should write complex sentences in your IELTS writing because they prove the expanded range of your grammar, earning you a higher band score.

You can use a mix of compound, relative, subordinate and conditional types to construct beautiful complex sentences that are simple to comprehend. Memorize common conjunctions and play with them in the structure of the sentence. Get the punctuation right so the examiner clearly understands the meaning of the complex sentence. Avoid complicating your writing and only use the type of complex sentence that you are confident of delivering it!

The critical point is to write them accurately, or you will lose a mark. So, practice, practice and practice writing complex sentences, and when you think you are ready, take an online IELTS mock test to have your writing assessed by a certified IELTS examiner and see if you are using them right.

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