If you had the chance to take a contract out on one punctuation mark, most people would probably choose the comma. Unfortunately, that’s not possible although modern journalists are doing their best to make it into an optional extra!

Punctuation should be there to help the writer and the reader, and the comma is no exception. If I know the rules for using commas, I expect one in certain situations and not in others. If there isn’t one when there should be, or there is one where there shouldn’t be, then I end up getting confused.

I may even have to re-read the passage to make sure I understand it. There are certainly ‘grey areas’ when even experts don’t know whether a comma is required or merely optional, but those should be the exception rather than the rule.

You might say that nobody has the right to decide what grammatical rules are ‘correct’ and that the plethora of rules I go by were taught to me back in the 1970s, but clarity comes first in my view, so here goes…

• Lists are the obvious example of using a comma. In the old days, people used to use what’s called an ‘Oxford comma’ before the word ‘and’, but we don’t any more, eg ‘I went to the market and bought apples, pears and bananas’. There are some circumstances when using the Oxford comma makes the sense of the text clearer, but most people would agree that you don’t need it. The list may also be a list of adjectives before a noun, eg ‘It was a juicy, ripe, delicious peach’.
  

• Conjunctions (or connectives) make two sentences into one ‘compound’ or ‘complex’ sentence with two separate clauses.
  • ‘Coordinating conjunctions‘ are used to make a ‘compound’ sentence when the clauses are equally important, and the two ‘main clauses’ should always be separated by a comma, eg ‘The sun was warm, but it was cooler in the shade’. There is a useful way of remembering the coordinating conjunctions, which is to use ‘FANBOYS’. This consists of the first letter of ‘for’, ‘and’, ‘nor’, ‘but’, ‘or’, ‘yet’ and ‘so’. If a FANBOYS word is NOT used to separate two clauses, then you don’t need a comma, eg in lists.
  • ‘Subordinating conjunctions‘ are used to make a ‘complex’ sentence when there is a main clause and a subordinate clause. (Subordinate just means less important.) If the sentence starts with a subordinating conjunction, the clauses need a comma between them, eg ‘Even though it was very hot, he wasn’t thirsty’. However, if the subordinate clause comes at the end, there is no need for a comma, eg ‘He wasn’t thirsty even though it was very hot’. There are lots of subordinating conjunctions, such as ‘after’, ‘although’ and ‘because’, but the easy way to remember it is to ask yourself if the conjunction is in FANBOYS. If it is, it’s a coordinating conjunction; if it’s not, it’s a subordinating conjunction. Alternatively, subordinating conjunctions are sometimes known as ‘WABBITS’ or ‘WABITS’ because some of the commonest ones start with those letters (when, where, while, after, although, before, because, if, though and since).

• Which (but not that) needs a comma before it when used as a relative pronoun, eg ‘The sky, which was tinged with orange, was getting darker before sunset’ or ‘He looked up at the sky, which was tinged with orange’. If you don’t know whether to use which or that, the word ‘which’ describes something, whereas the word ‘that’ defines it. The rule about commas also applies to ‘who’ when it comes to describing people, although you still use the same word whether you’re defining or describing someone. Relative pronouns such as ‘which’, ‘that’ and ‘who’ all create a relative clause, which is a type of subordinate clause, so the sentence will be a complex sentence.

• Openers (or sentence starters or fronted adverbials) are a useful way of starting a sentence, usually to specify a particular time, place or manner, eg ‘At half-past three, we go home to tea’, ‘At the end of the road, there is a chip shop’ or ‘With a smile on his face, he went to the ice-cream parlour’. They need a comma after them because the subject of the sentence (ie the noun or pronoun that governs the verb in the main clause) should come first.

• Direct speech needs something to separate what’s actually said from the description of who said it, and this is normally a comma (although it can sometimes be a question mark or exclamation mark if it’s a question or a command), eg
  “Hello,” he said.
  …or…
  He said, “Hello.”
  The tricky bit comes when the description of the speaker comes in the middle of what’s being said. Here, the rule is that a comma should be used after the ‘he said’/’she said’ if the speaker hasn’t finished the sentence yet, eg
  “On Wednesday evening,” he said, “we’re planning to go to the cinema.”
  When the sentence is over, though, you need a full-stop afterwards, eg
  “I like chocolate biscuits,” she said. “They’re so delicious.”

• Vocatives (people’s names or titles) and interjections are simply interruptions to a normal sentence – usually when someone is speaking – to include a name or words such as ‘well’ or ‘now’. They should be separated with one or more commas – even if that leads to a long list of words followed by commas, eg “Well, now, Mum,” he said, “let me explain.”

• Certain adverbs fall into the same boat, such as ‘however’, ‘nevertheless’, ‘furthermore’ and the humble ‘too’, and should be separated by commas, eg ‘She played on the swings and the roundabout, too.’

• Extra information (or embedded clauses or interrupters) is sometimes added to a sentence to describe something or someone. If the sentence would still make sense without it, you should put commas before and after the phrase to separate it from the rest of the sentence, eg ‘He stood, cold and alone, before his fate.’
  A tricky example of this is when you introduce people with a description of who they are, for example by saying ‘his best friend, James, is coming for dinner’. This is extra information, so there does need to be a comma before and after the word ‘James’. However, that’s only because the meaning is NOT changed by adding his name: nobody can have more than one ‘best friend’, so it HAS to be James, and including his name therefore makes no difference as to his identity.
  On the other hand, if you said ‘his friend James is coming for dinner’, you shouldn’t put commas around ‘James’ because James is not the man’s only friend – or let’s hope not, anyway!  Adding the name ‘James’ DOES change the meaning of the sentence, so it’s no longer just extra information.
• Present participles (ie verbs ending in -ing) are often used to describe what someone is doing, and they need to be separated by a comma, eg ‘He stood at the gate, jingling the keys in his pocket.’

• Eg and ie are useful shorthand to mean ‘for example’ (exempli gratia in Latin) and ‘that is’ (id est) and should be preceded by a comma, eg ‘He knew lots of poetic devices, eg metaphors and similes.’

• Names and places sometimes need a comma to separate their different parts. If the day comes after the month and before the year, it should have one, eg ‘December 7, 1941′. If someone has a qualification or letters after his or her name, you should use a comma, eg ‘John Smith, PhD’. If a town is followed by a state or country, the state or country should be separated by commas, eg ‘He lived in Lisbon, Portugal, for five years.’

• Numbers need commas to separate each power of a thousand. Start on the right at the decimal point and work left, simply adding a comma after every three digits, eg 123,456,789.0.

• Repetition of a word or phrase also demands a comma, eg “Half a league, half a league, half a league onward…”

Quiz

Put the correct punctuation in the following sentences:

1. I like music shopping and dancing
2. The food was good but he didn’t like the service
3. The book arrived after she went to the shops
4. He put on a jacket that was thick enough to keep out the cold
5. She called her mother which is what she usually did on Sunday evenings
6. At the end of the road he saw a fox
7. These apples are expensive he said
8. What are you doing she cried I need those biscuits for the charity bake sale
9. When Im on my own she admitted I watch a lot of daytime TV
10. Could you help me please David he asked
11. Fortunately he was experienced enough to avoid capsizing the boat
12. He stood nervous and bashful in front of the prettiest girl hed ever seen
13. He loved 19th Century novels eg Emma
14. She was persona non grata ie she wasnt welcome
15. He lived in Paris France
16. The Germans invaded Poland on September 1 1939
17. He watched 1001 Dalmations
18. All he could see was rain rain rain