Simple, compound and complex sentences explained for parents (Australia)

Your Year 4 child's writing comes home with a sticky note from the teacher: Great ideas! Next step: try using some complex sentences. Your child shrugs. You look at the story, see plenty of long sentences joined with "and then, and then", and wonder what counts as complex if those don't.

Simple, compound and complex are the three basic sentence types taught in Australian primary schools. The names sound technical, but the idea underneath is straightforward: it's all about how many ideas a sentence holds and how those ideas are joined together. Once you know what to look for, you can help with both reading and writing in a few minutes a day.

This guide explains clauses in plain language, each sentence type with clear examples, quick tests to tell them apart, why sentence structure affects reading comprehension, what the curriculum expects from Prep to Year 6, and games you can play at home.

Start with the clause

A clause is a group of words built around a verb, usually with someone or something doing it (the subject). "The kookaburra laughed" is a clause: kookaburra is the subject and laughed is the verb.

Clauses come in two kinds:

• An independent clause makes sense by itself and can stand alone as a sentence: The kookaburra laughed.
• A dependent clause has a subject and verb but leaves you hanging: because the dog slipped in the mud. You want to know what happened as a result.

Everything else in this guide builds on that difference. If your child is still unsure what a verb is, the guide to nouns, verbs and adjectives is a good first stop.

Simple sentences: one clause, one idea

A simple sentence has a single independent clause. It describes one event, action or idea.

• The bus was late.
• Jaxon kicked the footy.
• The tired old kelpie slept under the verandah all afternoon.

That last example surprises many parents. It's fairly long, yet it's still simple because it contains only one verb idea (slept). Length and type are not the same thing. Extra describing words and phrases make a simple sentence richer without changing its type.

Simple sentences are clear and punchy. Good writers use them on purpose, especially for drama: Then the lights went out.

Compound sentences: two equal ideas joined up

A compound sentence joins two or more independent clauses, usually with a coordinating conjunction. Each part could stand alone as its own sentence.

The coordinating conjunctions are often remembered with the word FANBOYS: for, and, nor, but, or, yet, so.

• I wanted a swim, but the beach was closed.
• Mum cooked the sausages, and Dad made the salad.
• We can catch the train, or we can walk.
• It started to rain, so we packed up the picnic.

Cover either half and the other still makes sense on its own. That's the clue that the ideas are equal partners.

Notice the comma before the conjunction in most of these examples. In shorter compound sentences many teachers let it go, but a comma before but or so is a helpful habit. The guide to punctuation covers commas in more detail.

Complex sentences: a main idea plus a supporting idea

A complex sentence has one independent clause and at least one dependent clause. The dependent clause is usually introduced by a subordinating conjunction, a joining word that shows how the ideas are connected.

Common ones in primary school include because, when, if, although, while, after, before, until, since and unless.

• We stayed inside because it was hailing.
• When the bell rang, everyone raced to the canteen.
• You can have dessert if you finish your veggies.
• Although she was nervous, Priya sang beautifully.

The bolded part can't stand alone. "Because it was hailing" is a fragment; it needs the main clause to finish the thought.

Complex sentences are powerful because the joining word tells the reader exactly how two ideas relate: cause (because, since), time (when, after, until), condition (if, unless) or contrast (although, while). That precision is why teachers nudge older children towards them.

Flipping the order

A dependent clause can go first or last. When it comes first, it's usually followed by a comma.

• We went to the park after we ate lunch.
• After we ate lunch, we went to the park.

Careful, though: After lunch, we went to the park is a simple sentence, because "after lunch" has no verb. It's a phrase, not a clause. Spotting that difference is a great Year 4 to 6 challenge.

The three types side by side

Two quick tests your child can use

The count-the-verbs test. Find the verbs (or verb groups). One verb idea usually means a simple sentence. Two or more means compound or complex.

The cover test. Cover one part of the sentence with a finger. If both parts make sense alone, it's compound. If one part leaves you hanging, it's complex.

Try them on "Lily laughed because the joke was silly." Two verbs (laughed, was), and "because the joke was silly" can't stand alone, so it's complex.

Why sentence types matter for reading

It's easy to think of sentence types as a writing topic only, but they affect how well children understand what they read.

Long sentences carry more load. A Year 4 reader meeting "Although the storm had passed, the river kept rising because water was still flowing down from the hills" has to hold three ideas and track how they connect. Children who can see the parts of a sentence are less likely to get lost. When a sentence confuses your child, the strategies in clarifying while reading help.

Joining words signal meaning. Because and so flag a reason or result, the backbone of cause and effect. When, before and after show order, which links to understanding sequence. Although and but point to contrast, useful when you compare and contrast.

Phrasing and expression. Readers who notice where clauses begin and end pause in sensible places, which makes reading aloud smoother. That's a big part of reading fluency.

Author's choices. Writers use short simple sentences to build tension and longer complex ones to slow down and explain. Noticing that is part of understanding suspense and how a text feels.

Why they matter for writing

Variety is the main goal. Writing made only of simple sentences sounds choppy: I went to the beach. It was hot. I swam. I had a pie. Writing made of endless "and then" sentences runs on and loses the reader.

Mixing the three types lets children show how ideas link: It was so hot that we raced into the water. After a long swim, I bought a pie, but a seagull stole half of it.

Two common problems teachers look for:

• Run-on sentences: several clauses squashed together with no joining word or punctuation. We went to the beach it was hot we swam.
• Fragments: a dependent clause left by itself. Because it was hot. This often appears when children start a sentence with because and forget the main clause.

Beyond the basics: embedded clauses

In the upper primary years, children meet clauses tucked inside other clauses, often starting with who, which or that.

• The girl who lives next door has a pet axolotl.
• The book that I borrowed was brilliant.

These are sometimes called embedded or relative clauses. They let writers pack extra detail into one smooth sentence. Most Year 6 children are still practising them, so don't worry if they feel tricky.

Where sentence types sit in the curriculum

Sentence structure is part of Language, one of three strands in the Australian Curriculum: English (version 9). In Foundation, children recognise that sentences are key units for expressing ideas. Year 1 students learn that a simple sentence is a single independent clause representing one event or idea. In Year 2, they learn to connect ideas with compound sentences made of two or more independent clauses, usually linked by a coordinating conjunction.

Year 3 introduces the clause as a unit of grammar, usually containing a subject and a verb that need to agree. Year 4 covers complex sentences: one independent clause and at least one dependent clause, typically joined by a subordinating conjunction to show relationships such as time and cause. In Year 5, students look at how writers use the structure of complex sentences for effect, and Year 6 explores how embedded clauses can expand complex sentences to elaborate and explain. Victoria's Curriculum 2.0 follows a similar progression, and schools choose their own teaching order within each year.

Sentence skills from Prep to Year 6

Prep: hearing and saying whole sentences; knowing a sentence starts with a capital and ends with a full stop. See Prep reading.

Years 1–2: writing simple sentences that make sense; joining ideas with and, but and so. Overviews: Year 1, Year 2.

Years 3–4: understanding clauses, using because, when and if, fixing run-ons. Guides for these years: Year 3, Year 4.

Years 5–6: choosing sentence types for effect, starting with a dependent clause, using embedded clauses. More detail: Year 5, Year 6.

Six games for home

1. Sentence stretch. Start with a simple sentence: "The cat sat." Take turns adding a joining word and a new idea. "The cat sat because it was tired." Keep going until it collapses into giggles.
2. Joining word cards. Write and, but, so, because, when, although on cards. Draw one and make a sentence using it about your day.
3. Finish my sentence. Say a dependent clause, such as "Unless it stops raining..." Your child finishes it.
4. Chop it up. Find a long sentence in a book. Can your child break it into shorter sentences that still make sense? Then glue them back together a different way.
5. Spot the type. While reading, point to a sentence and guess: simple, compound or complex? Check with the cover test.
6. Choppy to smooth. Write four short sentences about a weekend outing. Your child combines them into two better ones.

Keep sessions brief and fun. If practice becomes a battle, homework without tears offers gentler ways in.

Mix-ups worth expecting

Thinking long means complex. Remind your child to check the clauses, not the length.

"And then" everywhere. Not wrong, but repetitive. Offer alternatives: after that, when, so, but.

Starting with "because" and stopping. Read it aloud and ask "Because of that... what happened?"

Missing the comma after an opening clause. "When we got home we had dinner" reads more easily with a comma after home.

Confusing a phrase with a clause. "After lunch" has no verb, so it isn't a clause. "After we had lunch" does.

If sentences stay hard to follow

Most children grow into longer sentences with plenty of reading and talk. If a child in Year 3 or above regularly loses the meaning of longer sentences, can't retell what a paragraph said or writes only in very short, disconnected sentences, raise it with the teacher.

Broader reading worries are covered in signs a child is behind with reading and in when to worry about reading. No article can assess your own child, so if language or reading problems persist, talk with your child's teacher, a speech pathologist or a similarly qualified specialist.

FAQ

What is the difference between a compound and a complex sentence?

A compound sentence joins two ideas of equal importance with words like and, but or so, and each half could stand alone. A complex sentence has a main idea plus a supporting idea that can't stand alone, joined by words like because, when or although.

Can a sentence start with "because"?

Yes, as long as it includes a main clause too. "Because it was raining, we stayed home" is a correct complex sentence. "Because it was raining." on its own is a fragment.

What does FANBOYS stand for?

It's a memory aid for the coordinating conjunctions: for, and, nor, but, or, yet, so. These join independent clauses to make compound sentences.

What year do kids learn complex sentences in Australia?

Under version 9 of the Australian Curriculum, simple sentences appear in Year 1, compound sentences in Year 2 and complex sentences in Year 4, with more advanced structures in Years 5 and 6.

Try this tonight

When you finish a story together, pick one longer sentence and read it aloud. Ask your child to find the joining word and say what it tells you: a reason, a time or a contrast. One sentence a night is enough to make sentence types feel like a reading tool rather than a grammar lesson.

Curious where your child's reading sits right now? Try Ziado's free check, taking roughly ten minutes from home. Questions get easier or harder as your child goes, some results are shown right away with no account or card details needed, and signing up reveals the full placement. Sentence structure isn't reported as its own score, NAPLAN isn't what it's built for, and it can't diagnose dyslexia, language disorders or medical conditions. To see what everyday practice looks like, visit Ziado reading. Individual and Family plans start with 14 days free, and current prices sit on the pricing page.