Punctuation
Commas, semicolons, colons, dashes and apostrophes each have one job. Match the mark to the job.
The rules
- A comma plus a conjunction (and, but, so, or) joins two complete sentences. A comma alone cannot.
- A semicolon joins two complete sentences without a conjunction. Test it: could each side stand alone as a sentence?
- A colon must follow a complete sentence. It introduces a list, an explanation or an example.
- Use a pair of commas or a pair of dashes around extra information, never one of each. If you can remove the phrase and the sentence still works, it needs the pair.
- Do not separate a subject from its verb, or a verb from its object, with a single comma.
Watch out: A single comma splitting the subject from the verb ("The girl who won the race, was tired"). If a comma isn't doing one of the jobs above, it's wrong.
Worked example
My brother, who plays the cello practices every night. What punctuation is missing?
- The phrase "who plays the cello" is extra information.
- Extra information needs a comma before and after it.
- The correct version is "My brother, who plays the cello, practices every night."
Answer: A comma after "cello."
Try it yourself
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