Commas can cause a lot of confusion. People often ask me how to use them so I’m always on the look out for ways to explain them.
What about these guidelines from RL Trask in his book, the Penguin Guide to Punctuation?
He finds four types of commas:
Listing: use in a list where you could use ‘and’ or ‘or’ instead.
She used yellow, blue and brown pencils.
Joining: use to join two complete sentences with ‘and’, ‘or’ ,’but’, ‘yet’ or ‘while’.
The company has sold millions of products, but it has not yet made a profit.
Bracketing: use a pair of bracketing commas to set off a weak interruption.
The chef, hailed as the best in the world, has closed his restaurant.
I’m not so sure about the final type though. Seems to me it might be one that we could easily dispense with.
Gapping: use to show that one or more words have been left out when those words would repeat what has already been said.
Some students in the sixth form were puzzled by the exam; others, were enraged.
Trask says you can leave it out if the sentence makes sense without it and I think that will generally be the case.
There are more tips on commas in our grammar course.
Have you got any to add?