Count the main clauses: simple, compound, complex
The Short Answer
A simple sentence is one main clause with no subordinate clause. A compound sentence is two main clauses, usually joined by and, but or or, and sometimes by a semicolon. A complex sentence is a main clause plus a subordinate clause. So the question is really counting: find the clauses, decide which are main, and the label follows. A comma on its own is not a correct way to join two main clauses.
What is a sentence type question?
Your child is given a sentence and asked whether it is simple, compound or complex.
If they can already sort clauses, this question is arithmetic. If they cannot, it is guesswork — which is why we teach clauses first and treat this as the thing that follows.
The three labels
| Label | What it contains |
|---|---|
| Simple | One main clause, and no subordinate clause |
| Compound | Two main clauses joined by and, but or or (or by a semicolon) |
| Complex | A main clause plus a subordinate clause |
So the method is counting. Find the clauses. Decide which could stand alone. Read off the label.
The diagram shows one sentence of each kind, with the clause count that gives it its label.
Can you show me a worked example?
A comma does not make a compound sentence
This is the trap in this family, and it appears constantly.
The tide turned, the boats swung round.
Two clauses that could each stand alone — so far so compound. But there is no joining word, only a comma, and a comma on its own is not strong enough to hold two main clauses together. That is a punctuation error. The clauses have not gone anywhere; what is wrong is the join.
Mend the join and it is a correctly written compound sentence: The tide turned and the boats swung round, or, with a semicolon, The tide turned; the boats swung round. A full stop instead would make two simple sentences.
So there are two separate questions, and it helps to keep them apart. How many main clauses? is about structure. Are they joined correctly? is about punctuation.
Where do pupils lose marks?
Judging by length. A long sentence with one clause is simple; a five-word sentence with two is compound.
Missing a comma splice — counting two main clauses correctly and not noticing that the comma joining them is an error.
Stopping at the first verb and concluding there is only one clause.
Try it yourself
Find the clauses first and decide which could stand alone. Then name the sentence, or answer the question asked.
- The lanterns hung above the harbour.
- Nadia repaired the engine although the storm had started.
- Bilal spoke and the hall fell silent.
- Ola practised the violin until her fingers ached, and her brother waited outside. How many main clauses does this sentence have, and how many subordinate clauses?
- The tide turned, the boats swung round. How many main clauses are there, and what is wrong with the way they are joined?
- Simple. One main clause, nothing attached that has a verb of its own, and it stands alone.
- Complex. 'Nadia repaired the engine' is a main clause; 'although the storm had started' cannot stand alone, so it is subordinate.
- Compound. Two clauses, each of which would work on its own, joined by and.
- Two main clauses — 'Ola practised the violin' and 'her brother waited outside' — and one subordinate clause, 'until her fingers ached'. A sentence with both is called compound-complex. Where a question offers only simple, compound and complex, go by the definitions that question gives rather than a rule of thumb.
- Two main clauses, each of which would stand alone, joined by nothing but a comma. That is a punctuation error called a comma splice. The clauses are fine; the join is wrong. Written as 'The tide turned and the boats swung round', or with a semicolon in place of the comma, it is a correct compound sentence.
How much practice does this type need at home?
Build rather than label. Give your child a simple sentence — the lanterns hung above the harbour — and ask them to turn it into a compound one, then a complex one.
Making a complex sentence forces them to produce a subordinate clause, and producing one teaches the difference far more reliably than identifying somebody else's. It also takes about a minute, which means it can be done while the kettle boils.
Free: an English workbook
Questions across the English question types, with the method printed at the top and full answers at the back. One workbook for the whole strand, not a sheet per question type.
Frequently Asked Questions
Why does a comma not make a compound sentence?
Because a comma on its own is not a correct way to join two main clauses. A compound sentence joins them with a joining word — and, but, or — or with a semicolon. 'The tide turned, the boats swung round' has the two main clauses and only a comma between them, which is a punctuation error called a comma splice. The clauses are fine; the join is wrong. This matters because it appears in both the punctuation and the sentence type questions, wearing a different hat each time.
How does my child count the clauses quickly?
Count the verbs first, since every clause has one. Two verbs usually means two clauses. Then ask of each whether it would stand alone. That gives you the number of main clauses, and the number of main clauses is what decides the label — one with nothing else is simple, two is compound, and one plus a clause that cannot stand alone is complex.
What if a sentence has both a joining word and a subordinate clause?
Then it has two main clauses and a subordinate clause, and the name for that is compound-complex. If your child meets four labels, count properly: two main clauses and at least one subordinate makes compound-complex. Where only simple, compound and complex are offered, no single rule of thumb is safe, so go by the definitions the question itself gives and count the clauses against them. Counting correctly is the skill; the label follows from the wording in front of you.
Is a longer sentence always more complex?
No, and it is worth saying plainly. 'The exhausted climbers rested briefly beside the icy lake after their long ascent' is one main clause with a phrase attached — a simple sentence, despite its length. Meanwhile 'I ran and he followed' is compound in five words. The label is about clauses, not about length.
Sources
- GL Assessment — 11+ familiarisation materials and question type descriptions Published 2025.
- Clever Clogs Academy — our own Year 4 and Year 5 lesson records, Winslow Published September 2025 to July 2026.
We are not affiliated with, endorsed by or connected to GL Assessment or Buckinghamshire Council. Test arrangements change; always check the council's own pages for the current year's dates.
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