Complex Sentences: A Complete Guide For Primary Teachers

As your students become more confident writers, you'll probably notice that simple sentences start to feel a little limiting. Once they've mastered writing complete thoughts, the next step is learning how to connect ideas in more interesting and meaningful ways. That's where complex sentences come in.

Teaching complex sentences is an important part of English grammar, but it's also one of those skills that has a real impact across every area of writing. Learning to create variety through sentence structure improves every type of writing, from narratives to persuasive texts, even information reports. 

If you've already taught simple and compound sentences, introducing complex sentences is naturally the next step. Your students probably already use complex sentences every day when they're chatting with friends or telling you about their weekend. As students become more confident using different sentence types, their writing becomes more purposeful, engaging and enjoyable to read.

Complex Sentence Definition: A complex sentence contains one independent (or main) clause and at least one dependent (or subordinate) clause. These clauses are typically connected using a subordinating conjunction.

What Is a Complex Sentence?

A complex sentence contains one independent clause and one dependent clause (also called a subordinate clause). These two clauses are typically joined by a subordinating conjunction.

Unlike a simple sentence, a complex sentence allows students to connect ideas by explaining when, why, how, or under what conditions something happens.

For example:

Because it was raining, the students stayed inside during lunch.

Complex sentences help students explain their thinking, add meaningful detail and create more variety in their writing.

When introducing complex sentences to students, it can be helpful to look for three key parts:

• an independent (main) clause
• at least one dependent (subordinate) clause
• often, a subordinating conjunction that shows the relationship between the ideas

Let's take a look at these three parts of a complex sentence. 

The Key Parts of a Complex Sentence

One of the easiest ways to teach complex sentences is to break them into their individual parts. Once students understand what each part does, putting them together becomes much more straightforward.

We'll use the same sentence throughout this guide.

Because it was raining, the students stayed inside during lunch.

In this sentence:

• Independent clause: the students stayed inside during lunch
• Dependent (subordinate) clause: because it was raining
• Subordinating conjunction: because

Now let's understand each part in detail. 

Independent and Dependent Clauses

Every complex sentence contains two different types of clauses.

An independent clause expresses a complete thought and can stand alone as a sentence.

The students stayed inside during lunch. 

A dependent clause (also called a subordinate clause) cannot stand alone as a complete sentence. It relies on an independent clause to complete its meaning.

Because it was raining...

One simple question can help students tell the difference:

"Does this make sense on its own?"

If the answer is yes, it's an independent clause.

If the answer is no, it's a dependent clause.

Here are a few more examples of dependent clauses:

• Although she was nervous...
• When the bell rang...
• After the lesson finished...
• If you need help...
• Until the timer sounded...

Notice that none of these examples can stand alone as a complete sentence. Each one relies on an independent clause to complete its meaning.

Subordinating Conjunctions

A subordinating conjunction is a word that joins a dependent (subordinate) clause to an independent clause. It helps explain the relationship between the two ideas, showing when, why, where, under what conditions, or in contrast to something else.

Let's go back to our example:

Because it was raining, the students stayed inside during lunch.

In this sentence, because is the subordinating conjunction. It connects the dependent clause to the independent clause and explains why the students stayed inside.

Many students already use subordinating conjunctions naturally when they're speaking. Teaching them how these words work simply helps them use them more intentionally in their writing.

Some common subordinating conjunctions include:

• because
• although
• when
• since
• while
• if
• after
• before
• until
• unless
• whereas

Rather than asking students to memorise a long list, it can help to group these words by the relationship they show.

Check out the relationship association of common subordinating conjunctions in the list below:

Once students understand the purpose of each conjunction, choosing the right one becomes much easier than simply trying to memorise every word.

There are two acronyms commonly taught to help students remember subordinating conjunctions: I SAW A WABUB or A WHITE BUS. Both sets of displays can be downloaded for free from Mrs Learning Bee.

Download your free conjunctions displays here.

Complex Sentence Examples

Now that we've broken down the different parts of a complex sentence, let's see how they come together. As you read through the examples below, notice how each sentence contains an independent clause and a dependent clause, with a subordinating conjunction showing the relationship between the two ideas.

You'll also notice that complex sentences don't all begin the same way. A dependent (subordinate) clause can come before or after the independent clause, and some subordinate clauses can be embedded within another clause.

Showing students different complex sentence structures helps them create greater variety and make more deliberate choices in their writing.

Complex Sentences vs Compound Sentences

As students become more confident writers, they'll begin using a wider variety of types of sentences. It's helpful to compare simple, compound and complex sentences, as students can easily confuse the different sentence structures.

The easiest way to tell the difference between a complex and compound sentence is to look at the clauses.

A compound sentence joins two independent clauses, meaning both parts can stand alone as complete sentences.

For example:

The class finished early, so they played a grammar game.

Both clauses make sense on their own:

• The class finished early.
• They played a grammar game.

A complex sentence, on the other hand, combines one independent clause with one dependent (subordinate) clause. The dependent clause cannot stand alone because it doesn't express a complete thought.

For example:

Because the class finished early, they played a grammar game.

If you remove the independent clause, you're left with:

Because the class finished early...

Teaching students to ask, "Can this clause stand alone?" is one of the simplest and most effective ways to help them distinguish between compound and complex sentences.

Teaching Complex Sentences in the Classroom

The name might suggest otherwise, but teaching complex sentences doesn't need to be complicated. For example, start with “The students went outside.” Then give students a dependent clause or conjunction to work with: “when the rain stopped”, “although it was cold” or “because the sun came out.” Ask them to notice how each choice changes the meaning of the sentence.

You can model this live on The Hive's Buzzboard, colour-coding the independent clause in one colour and the dependent clause in another, so students can see how the two parts fit together.

As students become more confident, encourage them to think about why they're choosing a particular conjunction and how different sentence structures can change the meaning or flow of their writing. Understanding how independent and dependent clauses work also helps students avoid common mistakes such as run-on sentences and comma splices.

Complex Sentences Year 4

In Year 4, students develop their understanding that complex sentences contain one independent clause and at least one dependent clause, typically joined by a subordinating conjunction. They explore how clauses can be connected to show relationships such as time and causality, and apply complex sentences in their own writing.

The Hive has a range of teaching activities, explicit teaching slides and games to help students develop their understanding of complex sentences and subordinating conjunctions.

Explore all of our subordinating conjunction resources here.

Complex Sentences Year 5

In Year 5, students build on this knowledge by understanding that a complex sentence contains a main clause and at least one dependent clause. They explore how writers can use complex sentence structures deliberately for effect, helping them make more purposeful choices in their own writing.

Complex Sentences Year 6

By Year 6, students continue developing control over simple, compound and complex sentence structures, selecting and combining structures to express and connect ideas effectively. They can explore how conjunctions and clause choices help extend, elaborate and explain ideas in increasingly sophisticated ways.

Explore our complex sentence resources here.

Ready To Teach Complex Sentences? 

Teaching complex sentences is easier when your tools, lessons and resources live in one place. Inside The Hive you'll find Buzzboard for modelling and colour-coding clauses, sentence-building activities, Australian-curriculum grammar lessons and printable resources, plus planning tools to build it into your week.

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