Use commas correctly

Commas separate different parts of a sentence. There are many ways to use commas; however, people often use commas incorrectly, which can make their writing confusing. This article explains how to use commas correctly, and points out the most frequent mistakes people make with commas, so you can avoid them.

Ten ways to use commas correctly

Use a comma to separate items in a list

When you are using a list in a sentence, separate the items in the list with a comma. In British English it is usual to omit the comma before the final ‘and’ or ‘or’ in a list (the opposite rule applies in American English, and is called a ‘serial comma’). Here’s an example:

When we design the new community centre we will consult with local residents, community groups, businesses and authorities.

If leaving out the final comma could confuse your reader, keep it in. For example:

We had fish, potatoes, vegetables, and bread and butter.

Use a comma to separate non-essential items from a sentence

You can separate non-essential information from the rest of the sentence by using commas or round brackets.

We have requested, and are still waiting for, an answer to our questions.

Don’t use commas within commas. If your non-essential information contains commas, replace the commas with round brackets or en dashes, or separate the sentence into two sentences. Here’s an example:

Waka Kotahi, a government agency that invests in roads and rail, and walking, cycling and public transport, has its headquarters in Wellington. Incorrect

Here are three ways to rewrite this sentence to make it easier to read.

Waka Kotahi (a government agency that invests in roads and rail, and walking, cycling and public transport) has its headquarters in Wellington.

Waka Kotahi − a government agency that invests in roads and rail, and walking, cycling and public transport − has its headquarters in Wellington.

Waka Kotahi has its headquarters in Wellington. The agency invests in roads and rail, and walking, cycling and public transport.

Use a comma with a coordinating conjunction, if it helps avoid ambiguity

Coordinating conjunctions are ‘for’, ‘and’, ‘nor’, ‘but’, ‘or’ and ‘so’. They join two clauses in one sentence. It’s not essential to use a comma before a coordinating conjunction, but often it helps to avoid ambiguity.

System upgrades can be inconvenient, but they are necessary.

The new trail has excellent signage, so people won’t get lost.

Use a comma after an introductory phrase or a dependent clause

A dependent clause is a group of words that doesn’t express a complete thought. It cannot exist alone as a standalone sentence. It is correct to use a comma after a dependent clause, such as the dependent clauses shown in bold in these examples:

To get a promotion, you must work hard.

Since the COVID-19 lockdowns, many people have chosen to continue working from home.

Use a comma after a transitional element

A transition word or phrase links words, phrases or sentences. Phrases like ‘in other words’, ‘in spite of’, ‘in order to’, ‘on the other hand’ and ‘because of’ are all transition phrases. Use commas correctly by placing them after transitional elements like these ones shown in bold:

The people in our team are good at baking; in other words, we have fabulous morning teas!

As an illustration, this morning we had pavlova, chocolate brownies and fruit cake.

Here’s a complete list of transition words and phrases.

Use a comma to separate elements in your sentence that could confuse your reader

Without the comma in this example, the reader may need to read this sentence more than once to properly understand it.

When wet, tarpaulins should be laid flat to dry out.

Use a comma with quotations

Use a comma after ‘said’ to introduce a quotation, or to separate the quotation from the speaker.

The manager said to her staff, ‘Take the rest of the week off work.’

‘Take the rest of the week off work,’ said the manager to her staff.

If the comma is part of the quotation, place it inside the quotation marks.

‘Take the rest of the week off work,’ the manager told her staff, ‘but come in early on Monday’.

In the previous example, the full quotation would read: ‘Take the rest of the week off work, but come in early on Monday.’

Use a comma with coordinate adjectives

If you want to describe a noun with more than one adjective, it’s correct to use commas to separate them.

The long, winding, hilly road often gets closed in bad weather.

But, don’t use commas if the combination of adjectives makes one single entity.

My first car was an old red Ford Escort.

Use a comma to separate a name from a personal title

Each of these examples uses commas correctly. To check if your sentence is correct, remove the fragment enclosed in brackets – the sentence must still make sense without it.

Jacinda Ardern, New Zealand’s prime minister, spoke about the new policy.

Prime Minister Jacinda Ardern spoke about the new policy.

The Prime Minister, Jacinda Ardern, spoke about the new policy.

Use a comma to separate elements in place names

I went to school in Dallas, Texas.

She comes from Wellington, New Zealand.

Five situations when commas are not needed

Avoid adding commas when they aren’t needed, because this may change the meaning of your sentences.

Don’t use a comma after time when the time is integral to the point

Commas can indicate non-essential information. If your sentence includes a time that is essential to the meaning don’t separate it from the rest of the sentence with commas.

In 1995 a crucial piece of piece of legislation was introduced. Correct

In 1995, a crucial piece of piece of legislation was introduced. Incorrect

Don’t use a comma when a sentence contains an ‘if’ clause that is essential to the point

Commas can indicate non-essential information. If your sentence includes an ‘if’ clause that is essential to the meaning don’t separate it from the rest of the sentence with commas. You can test this by removing the clause altogether and seeing if the sentence still makes sense.

Our position is that if the minister asks for a briefing note we must make sure it is accurate and relevant. Correct

Our position is that, if the minister asks for a briefing note, we must make sure it is accurate and relevant. Incorrect

Don’t use a comma when words are placed next to each other for definition

Commas can indicate non-essential information. If your sentence includes words that are used for definition don’t separate them from the rest of the sentence with commas.

My colleague Jane always arrives on time for work.

In this example, because I have many colleagues, writing ‘Jane’ specifies which colleague I’m talking about. It is essential to the meaning of the sentence.

Grant Robertson, Minister of Finance, supported the new law.

In this example, ‘Minister of Transport’ is non-essential information as there is only one Grant Robertson.

Don’t use a comma when your sentence includes ‘that’ to define something

Commas can indicate non-essential information. If your sentence includes ‘that’ to define a clause don’t separate it from the rest of the sentence with commas.

The dog that needs clipping has brown paws.

This sentence means indicates there is more than one dog, but the one with brown paws is the one that needs clipping. See how separating this information with commas changes the meaning of the sentence:

The dog, that needs clipping, has brown paws.

Don’t use a comma to join two independent clauses

An independent clause is a group of words that expresses a complete thought. It can exist as a standalone sentence. To join two independent clauses into one sentence, use a coordinating conjunction or a semicolon.

For example, in this sentence the comma is incorrect:

It was raining, I drove to work. Incorrect

Here are some alternative ways to present this sentence:

It was raining, so I drove to work. Correct use of a coordinating conjunction.

It was raining; I drove to work. Correct use of a semicolon.

It was raining; therefore, I drove to work. Correct use of a semicolon

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