Compound sentence
A compound sentence joins two or more independent clauses of equal weight, linked by a coordinating conjunction, a semicolon or a colon: 'the lock turned and the door swung in'.
The lock turned, and the door swung in. Two clauses that could each be a sentence, joined as equals. That is a compound sentence.
How to build one
There are three ways to join two independent clauses:
- A comma plus a coordinating conjunction. The seven are for, and, nor, but, or, yet, so, often remembered as FANBOYS. I studied all night, but I still failed.
- A semicolon. More pause, and no stated relationship. I studied all night; I still failed.
- A semicolon plus a transition word such as however, therefore or meanwhile, with a comma after it. I studied all night; however, I still failed.
A comma alone is not enough. I studied all night, I still failed is a comma splice.
Compound sentence examples
- He rang the bell, and nobody came.
- You can wait here, or you can come with me.
- She was tired, yet she kept driving.
- The shop was closed; the lights were still on.
What coordination says
Joining two clauses as equals is a claim: they matter the same amount. That is often the right claim, as in He rang the bell, and nobody came, and the wrong one whenever a sentence is really about one thing with a condition attached. When every sentence on a page is compound, the prose reads as a list of equally important events, which is another way of saying nothing on the page is important. The fix is usually a complex sentence: demote one clause and the other rises.
Variants worth knowing
Drop the conjunctions entirely and you get asyndeton: The lock turned, the door swung in, the hall was empty. Repeat them past the point of need and you get polysyndeton: and the lock turned and the door swung in and the hall was empty. Same clauses, three different speeds.
Add a dependent clause to a compound sentence and it becomes a compound-complex sentence. And whether the main point comes first or last is a separate question, covered under loose sentence and periodic sentence.
Frequently asked questions
What is a compound sentence?
A compound sentence is two or more complete sentences, called independent clauses, joined into one. They are usually linked by a comma plus and, but, or, nor, for, so or yet, or by a semicolon.
Do you need a comma in a compound sentence?
Usually, yes: put a comma before the conjunction that joins the two clauses. Very short clauses can skip it ('I called and she answered'), and a semicolon replaces both the comma and the conjunction.
Is 'She locked the door and left' a compound sentence?
No. It has one subject with two verbs, which is a compound predicate inside a simple sentence. It becomes compound when the second half has its own subject: 'She locked the door, and she left.'