Broadly speaking, there are two main comma modes. One is pretty chilled, the other quite uptight. A Grateful Dead fan versus a pernickety traffic warden.
At its most relaxed, a comma is little more than a lilt in a sentence, a gentle pause. This is what the Chicago Manual of Style calls ‘the smallest interruption in continuity of thought or sentence structure’, considering its use to be ‘mainly a matter of good judgment, with ease of reading the end in view’.
Fiction writers will sometimes push this freedom to its limits. Cormac McCarthy once said that ‘if you write properly you shouldn’t have to punctuate’, and James Joyce tiresomely ended Ulysses on a twenty-four-thousand-word soliloquy containing only one comma and two full stops.
For most of us, though, these relaxed commas create pauses in which to draw breath; they help the reader ride the peaks and troughs of our rolling prose.
One way to sea-test your writing is to read it out loud. Seek out the natural pauses: these are often the places that deserve commas, which will usually help make your writing buoyant and intelligible. As a rule of thumb, you could add a comma at the points where subjects change in a compound sentence — for instance:
Three o’clock came and went. Fido nosed in the shrubbery for a bone that he had lost a week earlier, and I had a third cup of green tea to wash down the rather stale cake.
With shorter sentences, the comma becomes less necessary:
Three o’clock came and went. Fido searched the bushes for a lost bone and I had some more tea and cake.
A comma is omitted when two or more verbs share the same subject:
• Fido is forgetful in his old age and loses almost every bone we give him.
• Jamila drives a flashy new Peugeot and takes evening classes in postmodernist architecture.
In their more uptight mode, commas perform more critical functions.
You can use clauses and adverbial phrases.
• Jenny, who doesn’t suffer fools at the best of times, was livid.
• In readiness for the march, I put on my loudest pair of socks.
• Tomorrow, weather permitting, we’ll tour the new premises.
• Having polished off the cake, I went to help Fido.
• The bone, which lay among the dahlias, was grubby and smelly.*
*In this last example, the commas remove ambiguity. Without them, it might be assumed the writer was being restrictive in specifying a particular bone: this one among the dahlias, rather than that one among the lupins. (But this point also leads us astray on to questions of ‘which’ versus ‘that’, which warrants a separate post.)
You can address people.
• ‘Let’s eat, Grandpa.’
(Now try that sentence without the comma!)
• Cheers, Aunt Betty, I really wanted a pet pig.
You can list things.
Carefully, though. Here are two well-known examples of comma abuse:
- ‘To my parents, Ayn Rand and God.’
This (invented!) book dedication conjures an alarming mental image. To make good, we could add a comma after ‘Rand’, or reorder the dedicatees — for instance, ‘To God, Ayn Rand and my parents’.
- ‘Peter Ustinov retraces a journey made by Mark Twain a century ago. The highlights of his global tour include encounters with Nelson Mandela, an 800-year-old demigod and a dildo collector.’
This is a genuine TV listing from the newspaper. Mandela was many good things, but he wasn’t a centuries-old demigod with a penchant for sex toys. Again, a second comma or a reordering would clarify the sentence.
You can string together coordinate adjectives . . .
. . . but I won’t go too far into this because I reckon it deserves a blog post all of its own. Let’s just note for now that commas can often be omitted for fluency, as in the comment below by Clive James; ditto if the final adjective has a close relationship with the noun (e.g., ‘Berkshire pig’ or ‘pork sausage’, below).
‘Michael Howard looks like a small brown sausage.’
Bertie was a Berkshire pig. He was a beautiful Berkshire pig. He was a beautiful, big black Berkshire pig.
I ate three delicious pork sausages.
You can use appositives.
A term or phrase in apposition to a noun is separated by a comma.
• The school principal, Smedley, tried to soothe my irate mother.
• I sold it to my brother, Bill.*
*Watch out for restrictive appositives. In that second example, the comma tells us the writer has only one brother (‘. . . to my brother, who is Bill’). But if she had two brothers (say, Bill and Ted), the noun would need to assume a restrictive function and we would remove the comma: ‘I sold it to my brother Bill.’ By the same token: ‘I sold it to my brother Bill, and not to my brother Ted.’ ‘I sold it to my brother Bill, and not to my other brother, Ted.’
Commas doing other stuff
Commas feature in direct speech . . .
• ‘Bertie,’ said Betty wistfully, ‘was such a nice pig.’
• ‘Bertie was such a nice pig,’ said Betty wistfully.
. . . and in indirect questioning:
• I asked myself, would I have done the same?
Commas follow abbreviations such as ‘etc.’, ‘i.e.’, ‘e.g.’, ‘that is’:
• You’ll find knives, forks, spoons, etc., in the left-hand drawer.
Commas set off geographical terms:
• We wound up in Paris, Texas, rather than the French capital.
Q. What do commas and chinchillas have in common?
A. Soft pause.