The comma (,) is very frequently used and very frequently used wrongly. In fact, the rules for using commas are really rather simple, though complicated by the fact that the comma has four distinct uses. To begin with, forget anything you've ever been told about using a comma "wherever you would pause", or anything of the sort; this well-meaning advice is hopelessly misleading. In this document, the four uses of the comma are called the listing comma, the joining comma, the gapping comma and bracketing commas. Each use has its own rules, but note that a comma is never preceded by a white space and always followed by a white space.
Copyright © Larry Trask, 1997
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