Everyone is familiar with the comma. It’s a useful punctuation tool that can help to make sense of complicated sentences. But be wary! Used incorrectly, it can change the meaning totally…
Commas are used to mark a brief pause that’s much shorter than a full stop. It’s also used to separate words in a sentence to help make the meaning clear. This means they have to be used carefully or they can change the meaning of a sentence.
In this sentence the comma can save a life!
"Let's eat Grandma!"
"Let's eat, Grandma!"
The effect of not having a comma in the first sentence is that it reads as if you're eating Grandma, whereas, in the second, you're calling her to dinner (which is probably the intention – isn’t it?)
Commas in lists
Commas are used to separate the words in a list.
We will need hammers, nails and a saw.
Grandma is a cheerful, kind person.
He stopped, stared and ran.
Sam frightens the cat, teases the dog and annoys his neighbours.
Commas in long sentences
1. Two or more simple sentences that are joined together by conjunctions such as ‘but’, ‘or’, ‘so’ etc. are separated by a comma before the conjunction (joining word).
We queued for the concert for four hours, but we didn’t manage to get any tickets.
2. Complex sentences which are made up of main clauses and subordinate clauses need to be made clearer by commas separating the clauses.
When he saw the pirate ship on the horizon, the captain gave the alarm.
Commas with ‘and’
Commas aren’t generally used with ‘and’. However, sometimes it’s necessary to use a comma before ‘and’ to make the meaning clear.
I want to thank my parents, David Beckham and the Head Teacher. (This makes it sound like the parents are David Beckham and the Head Teacher. This is quite unlikely and needs to be made clearer.)
I want to thank my parents, David Beckham, and the Head Teacher. (This makes clear that all the people in the list are the ones being thanked.)
Commas to separate inessential words and phrases
Commas can be used to separate words that can be left out of a sentence without changing the overall sense of it, although they can add emphasis or meaning if they are left in.
1. The footballers, who were playing in the match, started to warm up.
In this sentence all of the footballers present were going to be playing in the match.
2. The footballers who were playing in the match started to warm up.
In this sentence it seems that there were footballers who weren’t taking part in the match.
Try reading the sentences below with and without the enclosed words and phrases to see how it changes the emphasis.
Harry Smith, our star player, broke his leg in the match last Saturday.
The man, who was wearing a blue hat, slid silently into the room.
The book was, without doubt, the best she had ever read.