Five Comma Rules for Essay Writing

As you become more able to express your ideas clearly and in sufficient depth, you will probably also become more adept at catching your own mechanics errors. This post is focused on one type of punctuation that serves several useful purposes and in the end makes it easier for your reader to understand you--the comma.

Here are the five situations in which you should use a comma:
1. In a compound sentence before the coordinating conjunction
2. To set off introductory elements, even a single word, from the main clause
3. To separate items in a series, following the A, B, and C model
4. To set off interrupting elements in the middle of the sentence
5. When two adjectives come before a noun

1. Compound sentences in fact don't always have a coordinating conjunction, what at our school we refer to as the FANBOYS (an acronym for the conjunctions thus used: for, and, nor, but, or, yet, so). That's because two independent clauses can be joined with a semicolon instead. However, when you do use the conjunction, it requires a comma. I call this the "married couple" rule for commas, as in, "The conjunction and the comma are a married couple. Put the comma with its spouse."

2. When you have an introductory word, phrase, or dep. clause ahead of your main clause, separate the two parts with a comma, so that the reader can easily follow your ideas as the sentence unwinds. This can begin to seem silly with single words such as "Then," or "Now," but for the present, follow the rule, so that you can become attuned to the general need for the comma there.

3. Believe it or not, there's a bit of controversy about the serial comma, since some stylistic experts feel quite strongly about which way to do it, as you come to the last item in your series. Follow the A, B, and C approach (with the comma before the last element--before the simple conjunction actually) for now, and as you become more confident as a writer, you can decide if you need that last comma or not.

4. Interrupting elements--what are those? Typically, they are phrases (or words) that could be placed elsewhere, but are being set here for emphasis, and require commas to keep the sentence's ideas clear. The key with these commas is that a writer must put one at the beginning and the end of the interrupting element.

Here are a few examples, some simple, some more complicated:

Martin Luther King, a civil rights activist, was arrested in Birmingham, Alabama in 1963.
Some in the movement criticized him; King decided, therefore, that he would write an essay to explain why he had been involved in the activities for which he was jailed.

He wrote a now-famous letter to other clergymen to explain why, under the circumstances, he had felt it necessary to lead protests in Birmingham at that time.

Some possible interrupting elements that might require commas include the following: appositives, conjunctive adverbs ("therefore" is one of them), restrictive clauses, and prepositional phrases. There are, of course, others.

One last important note about using interrupting commas. You will know you have placed the commas properly if everything inside the two commas could be pulled away, and the rest of the sentence still would make sense. The examples above pass this test.

5. Use a comma to separate two adjectives that come before a noun. This can be tricky, since sometimes one adjective really modifies the next adjective. If you can read the sentence with just one of the adjectives, and each time it makes sense, then you need the comma.

Example: He wore a fashionable, sporty outfit to the party.

BTW: Don't stack up more than two adjectives before a noun! It gets clunky.

I give you these guidelines with the understanding that, as with many such "rules," this advice is important to learn, but that gradually you may find you don't always need a comma in every case. What matters is that you know when a comma is technically called for, so that if you decide to leave it out, you know why stylistically it is acceptable, and that you are not creating confusion in so doing.