Simple, compound and complex sentences

Sentences can be simple, compound or complex. A simple sentence has one clause: ⟦The cat slept.⟧ A compound sentence joins two main clauses with ⟦and⟧, ⟦but⟧, ⟦or⟧ or ⟦so⟧: ⟦It was late, so we went home.⟧ A complex sentence has a main clause and a subordinate clause: ⟦We stayed inside because it was raining.⟧ Mixing all three makes writing interesting to read.

Key facts

• Simple: one subject and one main verb: ⟦My sister plays the piano.⟧ It can still be long: ⟦Every morning, Grandad reads the newspaper.⟧
• Compound: two clauses that could each be a sentence, joined by ⟦and⟧, ⟦but⟧, ⟦or⟧, ⟦so⟧: ⟦I like tea, but my brother likes coffee.⟧
• Complex: a main clause + a subordinate clause starting with ⟦because⟧, ⟦when⟧, ⟦if⟧, ⟦although⟧, ⟦until⟧, ⟦unless⟧…: ⟦Kai smiled when he saw the cake.⟧
• A subordinate clause first needs a comma: ⟦Because the road was icy, the bus was late.⟧
• Don't join two sentences with only a comma: ⟦It was cold, I put on my coat.⟧ is wrong. Use a full stop, a joining word or a complex sentence.

Worked examples