The Joining Comma

The joining comma is only slightly different from the listing comma. It is used to join two complete sentences into a single sentence, and it must be followed by a suitable connecting word. The connecting words which can be used in this way are and, or, but, while and yet. Here are some examples:

Norway has applied to join the EC, and Sweden is expected to do the same.
You must hand in your essay by Friday, or you will receive a mark of zero.
Britain has long been isolated in Europe, but now she is beginning to find allies.
Billions of dollars have been hurled into the Star Wars projects, yet we appear to have nothing to show for this colossal expenditure.
A dropped goal counts three points in rugby union, while in rugby league it only counts one point.

Remember, as I pointed out earlier, you cannot join two sentences with a comma unless you also use one of these connecting words. All of the following examples are therefore wrong:

*Bangladesh is one of the world's poorest countries, its annual income is only $80 per person.
*The British are notoriously bad at learning foreign languages, the Dutch are famously good at it.
*The proposal to introduce rock music to Radio 3 has caused an outcry, angry letters have been pouring into the BBC.
*Borg won his fifth straight Wimbledon title in 1980, the following year he lost in the final to McEnroe.

Joining two complete sentences with a comma in this way is one of the commonest of all punctuation errors, but one of the easiest to avoid if you pay a little attention to what you're writing. Either you must follow the comma with one of the connecting words listed above, or you must replace the comma with a semicolon.

Note also that most other connecting words cannot be preceded by a joining comma. For example, the connecting words however, therefore, hence, consequently, nevertheless and thus cannot be used after a joining comma. Hence the following examples are also wrong:

*Saturn was long thought to be the only ringed planet, however, this is now known not to be the case.
*Two members of the expedition were too ill to continue, nevertheless the others decided to press on.
*Liverpool are five points behind the leaders, therefore they must win both their remaining games.

Sentences like these once again require, not a comma, but a semicolon.

The rule is again easy:

• Use a joining comma to join two complete sentences with one of the words and, or, but, yet or while. Do not use a joining comma in any other way.

Copyright © Larry Trask, 1997

Maintained by the Department of Informatics, University of Sussex