Commas are a bit of a curiosity in writing because some people seem to use them very regularly while others never appear to use them at all. Not surprisingly, both approaches are wrong.
The comma is an important element of punctuation which is required in some circumstances and highly desirable in others. There are, however, some occasions where there is an element of choice and this is sometimes where people become a little uncertain.
Here are the main ways in which we use commas in English:
We use commas to separate items in lists:
- He put his torch, map, guidebook, sandwiches and a drink in his bag.
- The teacher said that he was lazy, insolent, aggressive and disruptive.
- He lives in Paris, shops in London, and holidays in Spain.
- He told me to park the car, pay at the machine, walk to the doors and wait for him.
Note how the last item is introduced with and but there is normally no comma, although see the third sentence.
However, there can also be some uncertainty with lists where an adjective is being modified in some way. For example:
- She was pretty wet and covered with sea-weed when I first met her.
Or could this be:
- She was pretty, wet and covered with sea-weed when I first met her.
- He described his approach as new, Labour, liberal, democratic and open.
Or could it be:
- He described his approach as new Labour, liberal-democratic and open.
We use commas to separate two independent clauses that are joined by words like and, but, or, nor, so:
- The path was steep, but the walkers were determined.
- The accident was due to carelessness, and he was very annoyed.
- All he had to do was to pay a small monthly sum, or so he thought.
(Note that an independent clause is a group of words that could stand alone as a sentence.)
We use commas to separate a dependent clause (introduced by words like as, because, since, when, after, while etc.) from a main clause:
- As she was tired, he carried her rucksack. (dependent clause followed by main clause)
- Because she had a headache, she stopped working for a while. (dependent clause followed by main clause)
(Note that a dependent clause cannot stand alone but must be linked to another clause.)
Commas are used after an introductory word or phrase, or before an afterthought:
- However, winters are not always cold and wet.
- Nevertheless, it’s time you started to take your work more seriously.
- First, before you do anything else, I want you to see a doctor.
- She wanted to do well but she didn’t, unfortunately.
They are used to enclose extra information that interrupts the flow of the sentence:
- The old dog, once so lithe and strong, was reduced to skin and bone.
- She is, in terms of her results, the best triathlete in the world.
- His jacket, or what remained of it, could not hide his injury.
We use a comma where we add in an appropriate name or descriptive phrase to add further information about an individual or an object:
- The youngest driver, Lewis Hamilton, was the winner.
- The driver, an unemployed Russian, had no licence or insurance.
- The judge, a very charismatic man, led the demonstration.
We find commas after time phrases:
- At 9 o’clock, the meeting started:
- By 2006, the evidence for global warming was overwhelming.
- By the time of his retirement, he was quite famous.
Commas are used to balance contrasting phrases:
- He might lose his hair, (but) never his sense of humour.
- He might bark, but he’d never bite.
- The meeting is on Tuesday, not Thursday.
Commas are important in direct speech:
- “He’s very angry,” she said.
- “I’ll always love you,” he murmured.
- “I’ll see what I can do,” he said, “but I can’t promise anything.”
We often use commas to avoid ambiguity:
- My second sister, who lives in France, is teaching English.
- I’m hot, and bothered about what to do with the children.
- I’m feeling sick, and tired of listening to this speech.
We use commas to show that some words have been left out:
- Birmingham and London are the preferred venues; Bristol, the other option.
- French and German are doing well; Chinese, much better.
We need commas with some types of clauses:
Commas are also very important with a special group of clauses which are called essential and non-essential clauses, also known as defining and non-defining clauses.