The Comma - 7 Rules

I’m kicking off this editing blog series with one of the trickiest of punctuation marks, the one that plagues us all – the Comma.

As a writer I often ask myself, have I put in too many? Have I put them in the right place?

There are many rules to the comma, and many involve all the technical words relating to sentence structure and breaking it down. But I am going to try and simplify this to make it easier for every day writers to understand – the writer who is initially more concerned with content than technical correctness. 

So here are 7 rules for the comma. Settle in, this could get lengthy:

1) A comma between two complete sentences:

One of the first tips I give when asked about comma placement, is one my English Language teacher used repeatedly:

‘Don’t put a comma where you can put a full-stop.’

If you have two complete sentences there is no reason to use a comma. To this day I say this to myself when writing, especially when unsure about the placement of a comma. 

2) A comma when using a connecting word between two complete sentences:

Use a comma between two complete sentences that are joined by But, Nor or For.

A comma is optional when joined by And or Or. A comma can be omitted when statements are short and closely related. 

But do NOT use a comma before And or Or unless there is a complete sentence on either side. If the second sentence depends on the first there is no reason for a comma – even when using a joining word.

For example:

It seems a small task but it’s not to be taken lightly.      

Close enough to watch her but far enough to avoid the unpleasant sound of her sobs

He turned his back to her and continued down the path.

3) The comma in lists and descriptions:

Use a comma between each item when listing a series of three or more words, phrases or clauses. For example:

Milk, bread, and cheese.

But don’t repeat the comma in a longer sentence:

Milk, bread, and cheese, were found on the table.

(The comma after cheese is wrong.)

In description, if you can insert the word ‘and’ between descriptive words, then a comma is required. For example:

Tall and dark and handsome = Tall, dark, handsome

Cold and shaking hands = Cold, shaking hands

But if the first descriptive word changes the second word, and the word ‘and’ would NOT work between them, then don’t use a comma:

High suspension bridge (can not be ‘high and suspension bridge’)

Long length of rope (can not be ‘long and length of rope’)

4) Use a comma to set off phrases and clauses within a sentence

a) When saying something in the middle of a sentence that is an aside or provides more information connected to the subject of the sentence, but is not the main point of the sentence:

She was, after all, right most of the time.

b) Using commas instead of brackets:

Wilson, who had travelled a long way, joined them at the table.

c) Identification or title:

John Smith, Senior Executive, was present.

d) Introductory words/Phrases/clauses

On the whole, he was glad she came. 

However, they decided that now was not the time.

5) When words demands a comma

Why a comma is needed – otherwise it might not make sense:

From behind her, feet pounded against the linoleum

6) Omitting words

Rather than repeat words in a sentence use a comma. For example:

John went to the pub for the company; Mark, for the darts. 

7) After introductory words or phrases, or abbreviations:

Use a comma after: For example, namely, that is

An abbreviation such as ‘i.e.’ is not followed by a comma, but ‘e.g.’ can be.

But it is optional to use one after: Furthermore, however, therefore, thus, nevertheless, consequently. 

Commas in the case of 'Which' and 'That':

'That' is a connecting word as it continues on the sentence. The information it provides is leading on from the first part of the sentence, so you do NOT require a comma. (rule 2)

He told me that it did matter to him.  

Although often in current writing we use it to start sentences when listing items, so then we would use a comma. (rule 3) For example:

He told me that it did matter, that it meant the world to him, that he couldn't live without it.

Whereas 'Which' leads to an aside or additional information so it would have a comma before it. (rule 4) For Example:

He thought it should be upside down, which looked better anyway. 

Jenny came into the shop and saw all the wool, which was on a huge display.

In this way we can also decide which word is appropriate as well - either 'which' or 'that'. 

(Note my use of 'which' in a different context, such as 'which one' hence no comma needed - told you it was tricky!)

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There are more rules for commas, but I feel these ones help clarify the majority of those needed in every day writing. 

Find more editing tip posts HERE. 

If you find any more, feel free to share them in the comments below.