There are 4 distinct uses of commas, which make the simple rules seem more complicated. Trask in The Penguin Guide to Punctuation calls them the listing comma, the joining comma, the gapping comma and the bracketing comma. (Click on menu for examples.)
Listing comma: use in a list where and or or would be possible instead (example: the three Musketeers were Athos, Porthos and Aramis). In British English it is not usual to put a listing comma before the word and or or itself since it is a substitute for the word and, not an addition to it. This type of comma is common in US English, and is also referred to as the Oxford comma. Where it is needed to make the meaning clearer, however, please do so.
Joining comma: use before and, or, but, yet or while followed by a complete sentence. It is thus used to join two complete sentences into a single sentence. You cannot join two sentences with a comma unless you also use one of these connecting words. So, either you follow the comma with one of these connecting words, or replace the comma with a semicolon.
Gapping comma: use to show that words have been omitted instead of repeated.
Bracketing comma: always come in pairs, unless one of them would come at the beginning or end of a sentence. They always set off a weak interruption which could in principle be removed from the sentence.
|Last modified:||15 September 2017 9.00 p.m.|