Comma On, Now!
Commas are, undoubtedly, a gray area when writing the English language. The key here – and in most places we are discussing conventions – is consistency.

Because language and conventions change over time, what you do today might not be considered “right” tomorrow, but as long as you are consistent within a document, fewer people will see your usage as “wrong.”

The Fewer the Better
With commas, a general rule of thumb to follow is “the fewer, the better.” DON’T believe that old saying of putting a comma everywhere you would pause for a breath when reading text out loud – you’ll end up with more commas and more inconsistent usage than you could imagine!

There are, however, a few places where commas should never go, as well as places where commas are expected. The following list reviews those places and offers examples to hopefully make comma usage a little clearer:

There should never be a single comma between the subject and main verb in a sentence OR between a verb and subject complement. Example – Last summer the same San Francisco court that shut down the old Napster, refused to do the same to the developers and distributors of Grokster and Morpheus software.

In the example, the subject is the noun, “court,” and the main verb is “refused.” Because you might want to emphasize certain parts of this sentence when it is read out loud, you might think you should put that comma in after “Napster.” But don’t. The convention is “no single comma between the subject and verb.”

So, what is the best way to correct it? First consider whether the sentence fits any of the categories below where the text requires a comma. If not, follow the general rule of thumb “the fewer, the better,” and don’t put one in, and definitely don’t expand it to two just so that it fits this rule.

Use a comma to tie two complete sentences together when they are joined by a coordinating conjunction. Example – The war on Internet piracy is raging, and now the Supreme Court is getting involved.

First, you need to know the coordinating conjunctions: and, but, or, nor, yet, for, so. Now take a look at the example. We have the complete sentence “The war on Internet piracy is raging.” We also have the complete sentence “Now the Supreme Court is getting involved.” They are joined by the coordinating conjunction “and.” In this example, the comma is correctly placed in front of the conjunction.

A comma should never tie two complete sentences together, all by itself. Example – The music labels appealed to the Supreme Court, a decision is expected some time this summer.

As you can see in the example, the comma is not correct. This is what, back in school, your teacher would call a “comma splice.” The sentence is actually two complete sentences (“The music labels appealed to the Supreme Court.” and “a decision is expected some time this summer.”) plopped side by side with a comma in the middle.

In order to correct the problem, you need to know that there are several ways to join complete sentences:

a. With a period and space – just two normal sentences side by side.

b. With a semi-colon.

c. With a coordinating conjunction and a comma, as listed in the previous tip.

d. With a variety of other punctuation marks (dashes, ellipses, etc.) that aren’t quite standard, but are becoming more so with the Computer Age.

Which method you choose is completely up to you. Many people have a tendency to see the three corrections in “a” through “c” as depending upon how closely the sentences need to be connected. If they aren’t really tied that closely together, then use “a.” For a little tighter connection, use “b,” and to show a clear connection, use “c.” For popular usage of the “d” method, see the later lesson in this series on The Computer Age and Writing.

Always use commas in lists. Example – Grokster has drawn extraordinary interest from groups like the Christian Coalition of America, the American Civil Liberties Union, the National Taxpayers Union and the commissioner of major league baseball. The example is punctuated correctly. However, an exception to the rule does exist. This particular rule is in transition right now: some people will insist on a comma before the word “and” that is between the last two items in the list, while others will insist no comma is necessary. This is one of those situations where consistency is more important than accuracy. Whichever way you choose, do it the same way throughout an entire document. Your company might even have editors or procedures that clarify existing company policy on the question of which method to use. • Always put commas around nonrestrictive information within a sentence. This can include appositives, non-restrictive relative clauses, and so on.

Example – The Pew Internet & American Life Project, a non-profit research group focusing on the Internet, said last week that some 17 million Americans are using a variety of technologies to get bootlegged music.

In the example, the commas enclose “a non-profit research group focusing on the Internet.” That noun phrase is an appositive for the subject noun phrase “The Pew Internet & American Life Project.” The appositive isn’t needed to explain WHICH Pew Internet & American Life Project is being talked about. If that were the case, the information would be restrictive (it would restrict the subject to a smaller group), and it would have no commas.

A simple example of this would be as follows:

Restrictive – The dog that barks a lot really gets on my nerves. Non-restrictive – The dog, which barks a lot, really gets on my nerves.

Here you can see that, in the first sentence, the relative clause “that barks a lot” restricts the possibilities for the subject: it’s only ONE dog we are talking about, the one that barks a lot. On the other hand, in the second example, the relative clause “which barks a lot” is just added information. Apparently, the reader/listener already knows WHICH dog the writer is talking about, so the additional information is offset by a pair of commas.

Use a comma to offset introductory information such as prepositional phrases, modifiers of time and place, conjunctive adverbs, relative clauses, and subordinate clauses. Example — In past piracy cases, the best the entertainment industry could hope for was a court order blocking a product from being manufactured.

The example is punctuated correctly by placing a comma behind the introductory prepositional phrase “In past piracy cases.” This convention is closely related to the previously listed one. Any time you have information at the beginning of a sentence that is really just additional information and not needed to form a complete sentence, it needs a comma behind it.

For a teaching lesson plan for this lesson see:
Business Writing Lesson Plan Introduction – Commas