Commas add clarity
Commas aid clarity, prevent ambiguity and indicate where you need to pause. Often you can tell if you need a comma by reading your work out loud though this won’t always work because punctuation is mainly for the eye, not the ear.
We tend to use more minimal punctuation today than we did in the past, and editors don’t always agree about whether a comma is necessary. Sometimes, if the meaning is clear either way, commas are a matter of personal preference.
At other times, commas – or the lack of them – can change the meaning. Some examples are:
A woman without her man is nothing.
A woman, without her, man is nothing.
He wasn’t killed mercifully.
He wasn’t killed, mercifully.
Writing clearly isn’t easy.
Writing, clearly, isn’t easy.
In all of the above examples, commas are used to prevent confusion. Here are some other guidelines to help you with the correct use of commas.
To separate items
Use commas to separate items in a series or list within a sentence, as in this example:
The details required are name, date of birth, address and phone number.
To provide extra information
Commas are used to set apart incidental or extra information that could be removed from the sentence without fundamentally changing its meaning. (These clauses are known as non-restrictive or non-defining). Compare:
All players who are now back in town deny the charges.
All players, who are now back in town, deny the charges.
Note that in the first example, there could be other players who are not back in town — there is no need for commas here. In the second example, all players deny the charges and, incidentally, they are all back in town. You need the commas in this sentence.
If the extra information is in the middle of the sentence, you must put a comma at either end. Often the extra information is introduced by the words which, who or while. For example:
The report, which we filed on Friday, was incomplete.
To separate clauses
You can use a comma to separate two independent clauses or ideas when they’re joined by any of these seven coordinating conjunctions: and, but, for, or, nor, so, yet.
The proposal looked promising, but some information was missing.
In my opinion, there is often no need for these commas if the meaning is clear without them.
After introductory statements
Use commas after introductory statements. For example:
On Tuesday 4 September, we plan to discuss the new housing development.
Although it rained all weekend, the convention was still held.
I’ve noticed that some writers are now omitting such commas if the meaning is clear.
With a string of adjectives before a noun
We often use commas with a string of adjectives before a noun.
The shrub has large, serrated, shiny, heart-shaped leaves.
As a rule of thumb, if you can reverse the order of the adjectives, use a comma. If you can’t reverse the order, you don’t need a comma. For example, compare:
The room was damp, dirty and untidy.
The girl had bright blue eyes and dark red hair.
To avoid repeating words unnecessarily
We use commas to avoid repeating words unnecessarily.
In 2000 there were seven cases; in 1999, five; and in 1998, four.
To prevent confusion at the end of a list
A comma is sometimes needed between the last two items in a list. This is known as the serial or Oxford comma.
They should seek the support of landholders, philanthropists, government, and community and industry groups.
An urban myth tells the story of a woman who left her estate to Jane, William, Mary and Anne. Jane and William argued that the estate should be divided into three, with Mary and Anne sharing a third. Use of an Oxford comma (Jane, William, Mary, and Anne) would have prevented this dispute.
Commas separate names from titles.
Ms Marika Weinberg, chief executive officer, presented the prizes.
If the title comes before the name, you don’t need commas, but most organisations use initial capitals (this is a question of style).
Managing Director John Smith proved an able leader.
Use commas before and after words and phrases that ‘interrupt’ the sentence. For example:
He is, however, going to sit the exam again.
She agreed, reluctantly, to re-sit the exam.
This article first appeared in Flying Solo.
Register for my online Grammar, Punctuation and Usage course.
Sign up for my monthly e-newsletter to receive writing and grammar tips.