Commas for Lists

I didn't know until today that commas are among the oldest of our modern punctuation marks, having been "invented" in stages by the Italians in the 15th and 16th centuries. According to punctuation guru Lynne Truss, commas serve two main functions: to indicate the grammar of a sentence and to emphasize elements such as "rhythm, direction, pitch, tone and flow."

Probably the first thing you learned about commas was that they're required to separate elements in a list. It's quite a simple rule, and generally doesn't lead to any discussion or disagreement, except in the case of the Oxford comma, which I defined in my last post. This rule is an example of a comma illuminating the grammar of a sentence.

Sometimes a list can be quite complex, however. Some sentences are made up of lists of phrases that contain other commas. This is where some writers might begin to worry about what they're doing.

Take a look at this example.

Spring is the busiest time for gardeners because they must plan their method of attack, prepare sites, fork compost, clear off mulch and other less valuable debris, divide perennials, prune trees, shrubs and vines, and sow seeds.

Note that I've used the Oxford comma here (the comma after the word vines) because I want to do all I can to aid my reader's comprehension.

In sentences like this one, a semi-colon could be employed to separate the various phrases from one another. But don't worry about that now. I'm getting ahead of myself. I won't be discussing semi-colons for weeks yet.

When using a comma to separate the items in a list, the rule is that the comma should be able to replace the word and or or.

In the gardening example above, the list-separating commas could all be replaced with the word and.
Except for the Oxford comma, of course. It's the exception to the rule.

Next time, I'll talk about using commas as list-separators when the list is made up of adjectives. I hope it will be an informative, useful and interesting post. (For some reason I didn't feel like using the Oxford comma here. Isn't English a wonderful language?)