So many writers are uneasy and unconfident about how to use commas, but though the humble comma has several different jobs, when you separate them out none is really very complicated. And commas really are crucial in helping you to say what you want to say and have the effect on your reader that you want to have. So here's a whistle-stop tour through the main ways that commas are used and useful, for you to play with and practice until this crucial tool comes naturally.
1) Commas in lists. Everyone knows this one:
- He bought fish, broccoli, a birthday cake and a sink plunger.
- He had long, dark, curly but rather lank hair
In American English, and at Oxford University Press, the "Oxford comma" is one popped in before the final "and":
- He bought fish, broccoli, a birthday cake, and a sink plunger.
And everyone puts a comma in before an and to make things clear when items in the list are themselves pairs:
- After supper they played Sardines, Cluedo, Hide and Seek, and Scrabble.
2) Joining Commas. I think of these as commas which link separate units of meaning - clauses - within a sentence: they quite literally articulate it. These examples definitely need a comma:
- Some separate off an opening clause or word from the main clause:
- Some separate off an ending clause after the main clause:
- All the soldiers got back safely, which we didn’t expect.
- I got stuck in a hole in the road, causing a terrible fuss when the tow-truck couldn’t haul the car out.
- He feels obliged to wade in and defend his friend, though it will delay him horribly
- Some work with a co-ordinating conjuction (and, but, or, while, or yet) to articulate two connected sentences. A comma might not be essential, but the sentence is often clearer and more rhythmic with one:
- I sleep, but he lies awake and reads.
- She hit him, and it was the only time she hit him.
- He swore never to do it again, yet the next day he got drunk, passed out, and woke up in a police station. [here, you definitely need the last comma, assuming he didn't pass out in the police station]
However, a comma is not strong enough to hold two complete sentences apart on its own; this mistake is called a comma splice. For that job you need a semi-colon or a full stop.
3) "Bracketing" or "parenthetical" commas separate out a clause which is a mild interruption to the main sentence. You should be able to remove the clause from inside the commas, and the sentence should still make sense.
- I sleep, which comes easily to me, but he reads for a while.
- He slept under a duvet, goose-down since you ask, and he'd never had such a good sleep in his life.
- If you asked me about my trip, though I bet you don't want to, you'd learn the most amazing things.
4) Gapping commas replace a word which would otherwise be clumsily repeated:
- I decided to go to sleep and the dog, to go hunting.
- Italy is famous for food and music but France, for wine and philosophy.
5) When one person addresses another, the name should be separated off with a comma:
- Aisha, can you grab my bag?
- Have you seen Billy, Kareem?
- I don’t like you, Carrie, and I don’t care who knows it.
- Fido's asleep, my Lord.
- But, madam, that’s your wretched husband all over. [Though, after reading this aloud, I'd be tempted to cut the comma after but.]
6) Reading aloud can help show where the commas should go, because you will naturaly separate out the separate units of meaning with a slight lift of the voice. However, punctuation has two jobs - to articulate the grammatical meaning and to express the way a voice would speak it - and sometimes they clash. To my mind, eye and ear, these have subtly different effects but are both perfectly correct:
- It began to rain as she walked away and, in battling with her umbrella, she stopped worrying about anything except keeping dry.
- It began to rain as she walked away, and in battling with her umbrella she stopped worrying about anything except keeping dry.
