Punctuation: The Comma and Its Uses

From the Oxford comma to an omission comma, the little curly punctuation mark is a small, simple thing that can cause so much confusion amongst writers. We probably all think we have an idea when it should be used and yet still puzzle over it at times.

Many people will tell you a comma is used as a natural pause in a sentence, particularly when a breath would be taken when reading out loud. Is that so?

In neither Strunk and White: The Elements of Style nor The Little Red Writing Book could I find anything that mentions a pause. Indeed, both books are quite specific about when commas should be used.

What is a comma?

Commas are used to break up sentences to make meaning. Take the title of a well-known book, Eats, Shoots and Leaves by Lynne Truss, which is described as ‘a hilarious tour through the rules of punctuation’. The title alone can have different meanings depending on how you write it, which is the point of the book.

Eats shoots and leaves (possibly a panda?)

Eats, shoots and leaves (a panda with a gun?)

Eats shoots, and leaves (a panda on his way somewhere after a meal?)

Eats, shoots, and leaves (a panda with a gun on his way somewhere after a meal?)

This quite clearly demonstrates the power of a simple mark to alter the meaning of a sentence.

Types of comma

The Little Red Writing Book suggests thinking of the comma as categorised into one of four types: a listing comma, a bracketing comma, a joining comma, or an omission comma. A small, simple thing starts to appear more complicated. But wait, the explanations will reveal that it is still simple, we just have to think of it in a different way.

Oxford serial listing comma

Also referred to as the Oxford comma – or serial comma – it is used when three or more items are listed within a sentence. As a general rule a comma goes after each item.

This one’s quite a controversial subject in writing circles too. Whether or not to use the Oxford comma.

There is a great article on Melissa Donovan’s blog, Writing Forward, about the use of serial commas. It’s well worth reading.

Both of the following examples are correct.

A writer’s materials consist of pens, paper, ink, and books

A writer’s materials consist of pens, paper, ink and books

The final comma preceding and is optional. If the sentence were to continue after the listed items with information other than the list itself, you would write it as follows:

A writer’s materials consist of pens, paper, ink, and books in abundance

A final comma after books is not necessary because abundance is not part of the list. Try re-writing the sentence with an additional comma and see how it looks and sounds.

Bracketing comma

For this one I shall be using words like parenthesis and parentheses. You need to get used to these words as you will come across them in most style books and authoritative books on writing. They’re more difficult to type than bracket, but I will persevere.

According to the Oxford Dictionary of English

Parenthesis a word or phrase inserted as an explanation or afterthought into a passage which is grammatically complete without it, in writing usually marked off by brackets, dashes, or commas      (parentheses) a pair of round brackets ( ) used to include such a word or phrase

So now you know. A parenthetical expression, or element, is one that gives additional information not essential to the sentence. Think of it as an aside, where the additional information is given to explain more about the essential part of the sentence.

The chauffeur, a tall man, wore a black uniform (a tall man is additional but non-essential information)

Don’t forget to close the additional information with a comma, otherwise you could be left with:

The chauffeur, a tall man wore a black uniform

This almost sounds like two separate sentences not necessarily related to each other.

When using the words which, when, and where in parenthetical expressions the comma precedes them.

The chauffeur’s uniform, which was neatly pressed, was black

The chauffeur, when he was working, wore a black uniform

Are there exceptions to the bracketing rule?

Yes, when one part of a sentence explains another and is put at the beginning of the sentence, or at the end of the sentence.

Having worked for the company for nine years, Chris was delighted when he finally got a pay rise

It’s almost as if the parenthetical expression has been moved from the middle of the sentence to the beginning. Following the bracketing rule, the sentence could have been written thus:

Chris was delighted, having worked for the company for nine years, when he finally got a pay rise

Joining comma

The words and, but, yet, nor, or, for all indicate a separate clause that could also be used as a complete sentence.

Chris had been quite happy working for the company for nine years, but he was disappointed that a pay rise had taken this long to come about

If you remove the comma and the word but and place a full stop (period) instead, you will have two separate sentences that say the same thing. As two sentences it may read in a halting manner and the use of the joining comma to unite the two clauses makes the sentence flow more pleasingly.

Chris is still waiting for his pay rise, by the way.

Omission comma

Commas can also be used to indicate a missing word, particularly and.

It was a long, poorly written, badly acted play with no intermission

If you can substitute any or all the commas with the word and then this is the correct use. The comma in this instance makes the sentence less tedious to read. An incorrect use of the omission comma might read:

The play was a long, poorly written, badly acted, affair with no intermission

The comma after ‘badly acted’ cannot be substituted by and, therefore it should not be there. The phrase ‘badly acted and affair’ does not make sense.


Don’t just pop commas in willy-nilly because you think they should be there. Readers generally know where to pause in a sentence and the proper use of commas will help by making the sentence legible and meaningful. Commas in wrong places will certainly make a reader pause. Not because you want them to, but because they are trying to make sense of what is being said.

When uncertain about the use – look it up. Read what you have written to yourself and decide what you are trying to say. Are you making an aside or putting in extra information? Are you writing a list? Are you joining two clauses together to make one sentence? Or are you omitting a word, like and?