Clauses and conjunctions

Main clause

A clause is a group of words built around a verb. A main clause makes sense on its own — it tells you what happened and who or what it happened to.

• the heron lifted off the water
• Amir counted the change twice

Give a main clause a capital letter and a full stop and you have a simple sentence: The heron lifted off the water.

Joining two main clauses

Two main clauses can be joined with a coordinating conjunction to make a compound sentence. There are seven, and the two halves stay equally important: and, but, or, so, for, nor, yet.

• The heron lifted off the water and the surface closed behind it.
• Amir counted the change twice but it was still short.

A comma alone cannot do this job. The heron lifted off, the surface closed behind it is the most common punctuation error in Key Stage 2 writing.

Subordinate clauses

A subordinate clause has a verb but cannot stand on its own. It begins with a subordinating conjunction — because, although, if, while, when, until, after, before, since, unless, whereas — and it needs a main clause to attach to. Together they make a complex sentence.

• Because the tide was rising — not a sentence; the reader is left waiting.
• We stayed on the rocks because the tide was rising. — now it works.

Either half can come first. When the subordinate clause comes first, put a comma after it: Because the tide was rising, we stayed on the rocks.

Relative clauses

A relative clause adds information about a noun and starts with who, which, whose, that, where or when. Dropped into the middle of a sentence, it takes a comma at each end.

• The heron, which had been standing there since dawn, lifted off the water.
• Amir, whose bus was already late, counted the change twice.

Cover the part between the commas and the sentence should still stand up. That is the test — and it is exactly what Relative Clauses KS2 practises.

The four sentence types

“Types of sentence” means two different things, and both come up in Key Stage 2. The sections above are about how sentences are built — simple, compound and complex. This one is about what a sentence does.

• A statement tells you something and ends with a full stop. The heron lifted off the water.
• A question asks something and ends with a question mark. Why did the heron fly away?
• A command tells someone to do something and usually starts with a verb. Watch the heron carefully.
• An exclamation shows strong feeling. In the national curriculum sense, an exclamation starts with What or How and contains a verb: What a noise that heron made! Many sentences end with an exclamation mark without being exclamations in this technical sense.

The two systems overlap rather than compete: a question can be simple or complex, and a command can contain a subordinate clause. A sentence always has both a structure and a job.

Adverbials are not conjunctions

Words like however, meanwhile, therefore, later that morning are adverbials. They link ideas, but they do not join two clauses into one sentence — the sentences stay separate.

• ✅ The rain stopped. Later that morning, the path dried out.
• ❌ The rain stopped, however the path stayed wet. — this needs a full stop or semicolon before however.

An adverbial placed at the front of a sentence is a fronted adverbial, and it takes a comma after it.

If you were taught the word connective at school, it covered both of these at once. The national curriculum dropped the term precisely because it hid the difference that matters here.