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Sentence Structure

This page about sentence structure will focus on the differences between simple sentences, compound sentences, complex sentences and compound-complex sentences.

You must know how to correctly write these sentence types for IELTS as the examiner will be looking for them when they grade you for your 'grammatical range'.

Clauses are the buliding blocks of sentences. So, before you go any further, make sure you understand what clauses are by looking at the previous lesson.

The Four Sentence Types

1. Simple Sentences

A simple sentence is one clause with a subject (S) and verb (V).

  • Computers are important in the modern world 
  • = SV

However, it can have more than one subject and verb:

2 subjects (SSV):

  • Computers and other technological devices are important in the modern world.

2 Verbs (SVV):

  • I search for information and play games on my computer.

2 subject and 2 verbs (SSVV):

  • My brother and I search for information and play games on our computers.

2. Compound Sentences

A compound sentence consists of 2 or 3 clauses. It is when simple sentences are joined together. In this sentence structure, the clauses are joined with the following coordinating conjunctions:

F = for
A = and
N = nor
B = but
O = or
Y = yet
S = so

The word 'fanboys' is an easy way to remember the different conjuntions that make up compound sentences. Obviously the most common are 'and', 'but', 'or' and 'so'.

Here are some examples of compound sentence structure:

Computers are important, but they can be dangerous too.

  • SV but SV

Computers are important, but they can be dangerous too, so we must be careful.

  • SV but SV so SV.

Avoid writing too many clauses as the sentence may get difficult to follow, and you cannot use each one more than once in a sentence to join clauses.

This is wrong:

Computers are used widely in most countries now and they are a sign of progress, and everyone should own one.

  • Incorrect formula = SV and SV and SV. X

Two possible corrected versions:

Computers are used widely in most countries now and they are a sign of progress. Everyone should own one.

  • Formula = SV and SV. SV.

Computers are used widely in most countries now and they are a sign of progress so everyone should own one.

  • Formula = SV and SV so SV.

Using semicolons

There is an instance when you can have a compound sentence structure without a coordinating conjuntion, and this is when you join two clauses with a semicolon. It is used when two ideas are related.

For example:

  • Computers are used widely in most countires; they are a sign of progress.

3. Complex Sentences

Complex sentences are more complicated (which is maybe why they are called 'complex'!).

This type of sentence structure is important for IELTS because to get awarded a band 6 or higher for your 'grammatical range and accuracy', you need to demonstrate that you are able to use them.

The more varied and the more accurate your complex sentences are, the higher the band score for this.

There are different types of complex sentences and these will be looked at in more detail later, so here you are just provided with the basics.

Complex sentences are two (or more) clauses joined together, but they are not joined by 'fanboys' (coordinating conjuntions). They are joined by subordinating conjuntions.

These are subordinating conjunctions:

as if
as long as
as much as
as soon as
as though

even if
even though
in order to
in case
so that


For example:

  • People take natural health supplements even though they may not have been tested.
  • Our children may not be properly educated if we don't spend more on schools.
  • I went to bed as soon as he left because I was tired.

These are all adverbial clauses. In these types of complex sentence, the second clause can be used to start the sentence. In this case, a comma is needed in the middle.

  • Even though they may not have been tested, people take natural health supplements.
  • If we don't spend more on schools, our children may not be properly educated.
  • As soon as he left, I went to bed because I was tired.

Noun clauses and relative clauses are also a type of complex sentence structure.

4. Compound-Complex Sentences

Compound-complex sentences are the same as complex sentences but they also have a simple (or compound) sentence before or after the 'complex' part.

For example:

  • I ate a lot when I got home, but I was still hungry.

The part that is underlined is the complex sentence. As you can see, it also has a simple sentences connected to it. It can also have a full compound sentence attached to it:

  • I ate a lot when I got home, but I was still hungry, so I went shopping to buy some more food.

These are compound-complex sentences.

Sentence Structure Quiz

Now have a practice in the quiz. Identify what type of sentence each is.
  1. I was late for work.





  2. He failed the test because he did not study hard enough.





  3. Even though pollution is widespread, people are doing little to prevent it.





  4. Animals should not be killed for their fur, but this is still occuring, so action must be taken.





  5. I came to study in the UK because I wanted to improve my English, so I talk to as many English people as possible.





More IELTS Grammar Lessons & Practice:

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