Complex Sentences for IELTS Writing and Speaking

Grammatical Range and Accuracy is a quarter of your Writing and Speaking scores, and one of the clearest signs of range is the ability to use complex sentences. But complex does not mean long and confusing. This guide explains what complex sentences are, shows five patterns that work well in IELTS Writing and Speaking, and helps you avoid the errors that cancel out the benefit.

What is a complex sentence?

A simple sentence has one clause: Cities are growing.

A compound sentence joins two main clauses with and, but or so: Cities are growing, and traffic is getting worse.

A complex sentence contains a main clause and at least one dependent (subordinate) clause, which cannot stand alone: As cities grow, traffic becomes worse.

The dependent clause adds a relationship between ideas: time, reason, condition, contrast or extra information. That is why complex sentences help you express more precise ideas, not just longer ones.

Why they matter for your band score

At the higher bands, examiners look for a wide range of structures and a good proportion of error-free sentences. At lower bands, candidates rely mostly on simple sentences, or attempt complex ones with frequent errors. So your aim is a natural mix: some short, clear sentences and some well-built complex ones, all mostly accurate.

Five patterns worth mastering

1. Relative clauses (who, which, that, where)

These add information about a noun.

• Students who study abroad often become more independent.
• Public transport, which is cheaper than driving, should be expanded.

Use commas around the clause when the information is extra (non-defining), as in the second example.

2. Adverbial clauses of reason and contrast

• Because housing is expensive, many young adults live with their parents.
• Although online learning is convenient, it can feel isolating.
• While some people prefer cities, others value the calm of the countryside.

3. Conditionals

Conditionals are excellent for Task 2 arguments and Speaking Part 3.

• If governments invested more in cycling lanes, fewer people would drive to work.
• Unless action is taken soon, the problem will become more serious.

4. Noun clauses

A whole clause acts as a subject or object.

• What worries many parents is the amount of time children spend online.
• It is often argued that university education should be free.

5. Participle clauses

These are compact and sound mature in writing.

• Having finished their studies, many graduates look for work overseas.
• Faced with rising costs, some families are cutting back on travel.

Make sure the subject of the participle is the same as the subject of the main clause, or the sentence becomes illogical.

Worked example: building complexity step by step

Start with three simple sentences:

Many people work from home. They save time. They sometimes feel lonely.

Combine them into one accurate complex sentence:

Although many people who work from home save time on commuting, they sometimes feel lonely.

This includes a contrast clause and a relative clause, and it expresses the idea more clearly than the three separate sentences. That is the goal.

Complex sentences in Speaking

In Speaking, complex grammar should sound natural rather than written. Useful spoken patterns include:

• I think the main reason is that ...
• If I had more free time, I'd probably ...
• It depends on whether ...
• The thing I like most about it is that ...

These fit especially well in Part 3, where you are asked to explain and speculate. See our post on giving developed answers in Speaking Part 3 for how to combine these with reasons and examples.

Common errors to avoid

• Fragments: Because the city is crowded. (a dependent clause on its own is not a sentence)
• Double conjunctions: Although it is cheap, but it is slow. (use only although)
• Run-on sentences: several clauses joined by commas without proper linking words.
• Wrong verb forms in conditionals: If I will have time, I will go. → If I have time, I will go.
• Overlong sentences: more than about 35 words is hard to control and hard to read.

Many of these also appear in our list of 10 common IELTS writing mistakes. Punctuation is closely linked to complex sentences, so it is worth reviewing the rules for commas with relative clauses too.

How to practise

1. Take a paragraph you have written and find three places where two simple sentences could become one complex sentence.
2. Choose one pattern a week and use it deliberately in every piece of writing and every speaking practice.
3. Read good-quality articles and notice how writers connect clauses.
4. Record yourself answering a Part 3 question and count how many complex sentences you used.

Our IELTS grammar guide explains each structure in more detail, with extra examples. When linking ideas, remember that clear logic matters more than fancy connectors; the IELTS Writing Task 2 structure guide shows how sentence-level and paragraph-level organisation work together.

Next steps

Pick two patterns from this post that you rarely use and write five sentences with each on common IELTS topics such as education, work and technology. Check every sentence for accuracy before adding more complexity.

To see how your grammar holds up under exam timing, take a free sample mock test.