Commanding the comma
The humble comma has to be one of the most used and abused pieces of punctuation besides the apostrophe, which I dealt with in a previous blog post, here. If you’re having trouble figuring out where to put your commas, you’re not alone. I don’t always get it right, either.
Some people suggest placing a comma where you might naturally pause when reading a piece of writing out loud. And yes, that works a great deal of the time. Unless you’re William Shatner
Punctuation rules, are for, people, who aren’t, William, Shatner.
So how do the rest of us know when to use a comma? Here are some useful rules.
In a list
Whenever you’re writing a list, you need a comma to separate each item.
At the supermarket, he picked up cat food, pizza, tonic water, and a large bottle of gin.
She packed a nightshirt, toothbrush, deodorant, and a hairbrush into her overnight bag.
The last comma in the list is known as a serial, or ‘Oxford’, comma and there are strong opinions about whether the serial comma is necessary. I like to use them to avoid confusion. With the Oxford comma:
I am inspired by my parents, Terry Pratchett, and Mary Wollestonecraft.
Without the Oxford comma, this becomes:
I am inspired by my parents, Terry Pratchett and Mary Wollestonecraft.
As impressive as having Terry Pratchett and Mary Wollestonecraft for parents might be, I’m very attached to the mother I already have. It’s best to avoid that kind of ambiguity.
When there are two clauses that could each stand as a complete sentence in their own right, we call these independent clauses. We only use a comma between two independent clauses if there is also a conjunction (and, if, or, but).
Fifteen minutes of reading in bed at night helps my mother fall asleep, but if I read in bed, I get too engrossed and end up staying up half the night.
If we don’t use a conjunction and if the clauses are related to one another, we use a semi-colon.
Fifteen minutes of reading in bed at night helps my mother fall asleep; if I read in bed, I get too engrossed and end up staying up half the night.
If the clauses are unrelated, we make them into two separate sentences with a full stop.
Fifteen minutes of reading in bed at night helps my mother fall asleep. The first thing she does in the morning is make a cup of tea.
We don’t use a comma on its own to separate two independent clauses.
Fifteen minutes of reading in bed at night helps my mother fall asleep, if I read in bed, I get too engrossed and end up staying up half the night.
This is known as a comma splice and should be avoided.
Separating dependent clauses
We use commas to separate dependent clauses from the main clause in compound sentences. The main clause is one that could stand alone as a sentence.
I love cats.
A dependent clause is one that can’t stand alone and needs the main clause to give it meaning.
I love cats, they are so amusing to watch.
As you can see, the comma in this case comes after the main clause. Sometimes we put the dependent clause first, but we still use a comma between them.
After the concert, we drove home.
A dependent clause beginning with ‘who’, ‘which’, ‘that’, ‘whom’, or ‘where’, is known as a relative clause. There are two kinds of relative clauses: non-restrictive and restrictive.
Non-restrictive relative clauses
When a clause can be removed from a sentence and the sentence still makes sense (usually a bit of extra information), we call it a non-restrictive relative clause. We place a comma either side of this clause.
The tall gentleman with the umbrella, who was at the front of the train, waved his newspaper to catch her attention.
We can take out the clause that sits between the commas and the sentence will still make sense. We just lose that bit of extra information.
The tall gentleman with the umbrella waved his newspaper to catch her attention.
Restrictive relative clauses
When a piece of extra information is essential to the meaning of the sentence, we call it a restrictive relative clause. In this case, we don’t use a comma either side.
People who have big heads need large hats.
If we remove the clause, the meaning is altered.
People need large hats.
An aside works in a similar way to a non-restrictive relative clause. It’s a part of the sentence that can be taken away without altering the meaning. We always use commas at each end of an aside.
My mother is, of course, a very independent woman.
Without the aside, the sentence means the same.
My mother is a very independent woman.
With direct speech
We need a comma before direct speech begins, if it’s at the end of a sentence. The comma always comes before the quotation marks.
Sophie looked sideways at Dave and said, “My favourite part was where you interrupted, every time I spoke.”
When the speech comes at the beginning of a sentence, the end comma comes before the quotation marks.
“I think we need to take this out of the meeting, otherwise we’re going to run out of time,” Jenny said.
Of course, if the speech is a question or an exclamation, we’d use the proper punctuation mark in place of the comma.
“Do you seriously have to try to explain everything for me, Dave?” Sophie asked.
I hope this helps you to decide whether or not to use a comma. If there are any situations you think I’ve missed, let me know in the comments and I’ll add them.