Several business writers have told me they were taught never to put a comma before ‘and’. Now, I could understand if they’d been told not to put one after ‘and’, but before? So I decided to look at occasions when we can use a comma before ‘and’.

There are two occasions where a comma can be used before ‘and’:

• Serial comma (also called the Oxford comma)
• Coordinating conjunctions (joining words)

Serial commas can add clarity

The serial comma is used before a final ‘and’ in a list for clarity.

An urban myth is that a woman left her estate to John, Martha, Alan and Joyce. John and Martha argued that the estate should be divided into three and that Alan and Joyce should share a third.

Another example given on Wikipedia is:

To my parents, Ayn Rand and God.

Some writers go overboard with the serial comma and use it in every list with a final ‘and’. I think that’s unnecessary. Let sense dictate usage, and use a serial comma only when it adds clarity.

And is a coordinating conjunctions

The traditional rule is that you should put a comma before a coordinating conjunction that joins two clauses of equal weight. The most common coordinating conjunctions are known as the FANBOYS – for, and, nor, but, or, yet and so.

The following examples are from YourDictionary

She did not cheat on the test, for it was not the right thing to do.
They got there early, and they got really good seats.
There was no ice cream in the freezer, nor did they have money to go to the store.
I would have gotten the promotion, but my attendance wasn’t good enough.
I think I will buy the red car, or I will lease the blue one.
I am counting my calories, yet I really want dessert.
He ran out of money, so he had to stop playing poker.

In my opinion, you can often omit the comma if the sentence is clean and clear without it. In several of the above sentences, I would leave out the comma.

Read different newspapers online and look at the way writers use commas. There is a huge variation in usage because we use commas based on both syntax and sound. Many of the commas that were traditionally used to indicate a pause are dropping out if the meaning is clear.

In 2010, we introduced new policies.
In 2010 we introduced new policies.

Most of the time, comma usage is not an issue unless the punctuation trips us up or is ambiguous. That doesn’t stop people debating usage. The following dedication in Lynne Truss’s book on punctuation (Eats, Shoots and Leaves) caused controversy because of the position of a comma.

In the memory of the striking Bolshevik printers of St Petersburg who, in 1905, demanded to be paid the same rate for punctuation marks as for letters, and thereby directly precipitated the Russian Revolution.

It was not her comma before ‘and’ that caused the controversy, but her lack of a comma before ‘who’. I would not have punctuated that sentence the way she did, but she had her defenders, who argued that a comma before ‘who’ would have led to a comma overload.

How would you have punctuated her sentence? I think I would have broken the sentence into two to avoid the clumsy punctuation.

If only punctuation was black and white!

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