How to use Commas

1. The comma [,] is used to show a slight pause in a sentence.

2. It is the lightest mark of punctuation.

3. It is also used to separate and clarify clauses.

He will never do it, whatever he says.

She bought some butter, a pint of milk, and some jam.

Cars should turn left here, whilst vans should turn right.

4. The comma is used to separate words, clauses, or phrases.

5. It separates two clauses when the first is not closely associated with the second:

She is a famous singer, whilst her husband remains unknown.

6. It is used to clarify the sense of statements and to prevent ambiguity.

7. It creates a pause where you might mistake the sense of what is written:

AMBIGUOUS
In the valley below the villages looked small.

CLEAR
In the valley below, the villages looked small.

8. It separates a sequence of adjectives qualifying a noun:

He was an arrogant, pompous fellow.

9. But when the adjectives are of a different order, no comma is necessary:

He was a distinguished foreign visitor.

10. It marks a parenthetical phrase within a sentence:

I am quite sure, despite my reservations, that he's the best man for the job.

11. A very common use for the comma is to separate the items in a list:

The box contained a book, some pencils, and a knife.

12. Opinions differ on the need for the final comma in such examples. If the items are all of the same kind, it can usually be omitted. If they are not, it is safer to retain the comma. This is sometimes called the 'Oxford comma'.

13. The need for it is very well illustrated by this howler from a best-selling novelist:

"This book is dedicated to my parents, Anne Rice and God."

14. Sometimes confusion is created by the insertion of commas where they are not really necessary. This is an example of bad usage:

The strangest of all these new sensations, was the onset of profound happiness.

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15. Commas should not be used to connect separate sentences as a casual substitute for the full stop:

A party has been arranged, it will not take place until next week.

A party has been arranged, but it will not take place until next week.

16. Even though in some cases a comma may not be absolutely necessary for retaining grammatical coherence (as in the previous example), it may still be useful in order to clarify the meaning for a reader. Here's another example of poor writing.

Each night you stay at a Roberts-Plaza Moat Houses UK hotel at the fully published or corporate rate you are entitled to a special discount voucher.

Each night you stay at a Roberts-Plaza Moat Houses UK hotel at the fully published or corporate rate, you are entitled to a special discount voucher.

17. What follows is an example of an entire paragraph which has been punctuated using only the comma and the full stop.

The central thought or main controlling idea of a paragraph is usually conveyed in what is called a topic sentence. This important sentence which states, summarises or clearly expresses the main theme, is the keystone of a well-built paragraph. The topic sentence may come anywhere in the paragraph, though most logically and in most cases it is the first sentence. This immediately tells readers what is coming, and leaves them in no doubt about the overall controlling idea. In a very long paragraph, the initial topic sentence may even be restated or given a more significant emphasis in its conclusion.