Clauses and conjunctions

Main clause

A clause is built around a verb. Many clauses also name a subject. A main clause can form a complete sentence, describing an action or a state.

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

This example is a simple sentence, with a single clause: The heron lifted off the water. It starts with a capital letter and ends with a full stop.

Joining two main clauses

A coordinating conjunction, such as and, but or or, can join words, phrases or clauses of equal grammatical status. Joining two main clauses in this way makes a compound sentence.

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

In Standard English writing, avoid joining two main clauses with only a comma. This is called a comma splice: The heron lifted off, the surface closed behind it. Use suitable punctuation or a conjunction to connect the ideas.

Subordinate clauses

A subordinate clause is grammatically dependent on another part of the sentence. Some begin with a subordinating conjunction, such as because, although or if. Relative clauses are another type of subordinate clause, so a conjunction is not the starting point of every subordinate clause.

The examples below use adverbial clauses, which explain a reason, time or condition. A main clause with a subordinate clause forms a complex sentence.

• Because the tide was rising is a subordinate clause. This example leaves the reader waiting for a main clause.
• We stayed on the rocks because the tide was rising. combines a main clause and a subordinate clause.

These adverbial clauses can come before or after the main clause. Use a comma after a fronted adverbial clause: Because the tide was rising, we stayed on the rocks. Other subordinate clause types do not all follow this pattern.

Relative clauses

A relative clause gives information about a noun. It can begin with who, which, whose, that, where or when. In some relative clauses, an object relative pronoun can be left out: The book that I chose was about birds can become The book I chose was about birds.

Use commas when a relative clause adds extra, non-essential information. When this clause sits in the middle of a sentence, use a comma at each end. A clause that identifies which person or thing you mean has no separating commas, as in the book example above.

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

The extra information in these two comma-marked examples can be removed while leaving the main clause intact. Grammar alone is not the whole test: decide whether the information identifies the person or thing. Relative Clauses KS2 practises the extra-information pattern with paired commas.

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 its grammatical form and usual purpose.

• A statement has declarative form and usually gives information. It often ends with a full stop, but can end with an exclamation mark. The heron lifted off the water.
• A question has interrogative form and usually asks for information. It is normally written with a question mark. Why did the heron fly away?
• A command uses imperative form to tell someone what to do. The subject you is often left unstated. It can end with a full stop or an exclamation mark. Watch the heron carefully.
• An exclamation can express strong feeling using a What or How pattern: What a noise that heron made! An exclamation mark can also end a statement or command, so punctuation alone does not identify the grammatical form.

See the DfE Writing Framework, page 110, for sentence-form examples. A question can be simple or complex, and a command can contain a subordinate clause. A sentence has both a structure and a job.

Adverbials are not conjunctions

An adverbial adds information, such as time, place or manner. Some adverbials, such as however, meanwhile and therefore, also help link ideas. They do not act as coordinating conjunctions between two main clauses. A full stop can separate those clauses, or a semicolon can connect them.

• ✅ 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 before the main clause is a fronted adverbial. The English curriculum for England teaches a comma after fronted adverbials.

Connective may be used as a broad classroom label. Identify the word’s grammatical job in the particular sentence, using terms such as conjunction and adverbial.