Punctuation: commas (,)

 We use commas to separate a list of similar words or phrases:

It’s important to write in clear, simple, accurate words.

They were more friendly, more talkative, more open than last time we met them.

We do not normally use a comma before and at the end of a list of single words:

They travelled through Bulgaria, Slovakia, the Czech Republic and Poland.

American English does use a comma in lists before and:

We took bread, cheese, and fruit with us.

We use commas to separate words or phrases that mark where the voice would pause slightly:

I can’t tell you now. However, all will be revealed tomorrow at midday.

We had, in fact, lost all of our money.

James, our guide, will accompany you on the boat across to the island.

Separating clauses with commas

When main clauses are separated by and, or, but, we don’t normally use a comma if the clauses have the same subject. However, we sometimes use commas if the clauses have different subjects:

They were very friendly and invited us to their villa in Portugal. (same subject)

Footballers these days earn more money but they are fitter and play many more matches. (same subject)

It was an expensive hotel in the centre of Stockholm, but we decided it was worth the money.(different subjects)

When a subordinate clause comes before the main clause, we commonly use a comma to separate the clauses. However, we do not always do this in short sentences:

If you get lost in the city centre, please don’t hesitate to text us or phone us.

If you get lost just phone us.

When we use subordinate or non-finite comment clauses to give further details or more information, we commonly use commas to separate the clauses:

You do need to wear a darker jacket, if I may say so.

To be honest, I thought they were very very rude.

Commas and relative clauses

We use commas to mark non-defining clauses. Such clauses normally add extra, non-essential information about the noun or noun phrase:

The ambulance, which arrived after just five minutes, took three people to the hospital immediately.

Hong Kong, where the first ASEAN meeting was held, is a very different city now.

The same is true for non-finite clauses:

The storm, lasting as it did for several days, caused serious damage to villages near the coast.

Warning: 

We don’t use commas to mark defining clauses:

Barcelona was the Spanish city that was selected for the Olympic Games.

Not: … the Spanish city, that was selected …

Commas and speech forms

We commonly separate tags and yes-no responses with commas:

They are going to the party, aren’t they?

No, thank you. I’ve already eaten too much.

We also usually separate vocatives, discourse markers and interjections with commas:

Open the door for them, Kayleigh, can you. Thanks. (vocative)

Well, what do you think we should do about it? (discourse marker)

Wow, that sounds really exciting. (interjection)

We use commas to show that direct speech is following or has just occurred:

He said in his opening speech, ‘Now is the time to plan for the future.’ (or He said in his opening speech: ‘Now is the time to plan for the future.’)

When the direct speech is first, we use a comma before the closing of the quotation marks:

‘We don’t want to go on holiday to the same place every year,’ he said impatiently.