Grammar: Your Friend, The Comma

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When I first started this website, I didn’t think I’d be writing many– if any– posts about grammar. Then… well, I thought about papers my students and classmates had me review. One thing became abundantly clear: people have no idea how to use commas.

Fear not. I use commas all the time, and I’ll clear up any confusion surrounding the matter.

First, I’d like to point out the most common mistakes people make with commas.

1. Comma splicing.

This is when two independent clauses are connected with a comma, when they should be connected with a semicolon. Here’s an example:

The man couldn’t see out the window, it was very dark outside.

Because the two clauses are related, it’s okay to put them in the same sentence– sometimes, it’s better that way. But they shouldn’t be separated by a comma. Use a semicolon instead, and you have a perfectly good sentence.

2. Failing to include the comma within quotation marks.

This is pretty basic, but I see it all the time. When you use a quote in a sentence, the comma– in fact, all punctuation— goes inside the closing quotation mark. Don’t do this:

“Lemarck was wrong about acquired traits”, claimed Frederick.  

It’s never correct. Instead, it should look like this:

“Lemarck was wrong about acquired traits,” claimed Frederick.

3. Inserting a random comma in between subject and predicate.

Some sentences seem to entice people to put in an extra comma in order to break up the individual words into smaller pieces. Do not fall prey to their intoxicating lures! It is a trap! For example, this sentence should not have a comma:

Two flugelhorn players and their pet dogs, searched for the missing manuscript.

There’s no reason for the comma to be there. So, you know, don’t put one there.


Here is when you should use commas:

1. When separating items in a list or series.

This is the first one you learn in elementary school. I don’t feel the need to explain it too much, so here’s an example:

The spell required chicken blood, snake venom, rat tails, and the tears of a virgin princess.

2. Before a coordinating conjunction in a series.

That last comma after “rat tails” in the above example is called an Oxford Comma. Technically speaking, it doesn’t need to be there; the “and” serves the same function. However, when writing academically, it is required by the MLA, APA, and Chicago style guides, so use it.

3. Before a small conjunction and a subsequent independent clause.

This one can be a little tricky. Small conjunctions are words like “and,” “but,” “yet,” “so,” “or,” and “for.” You should use a comma combined with a small conjunction to connect independent clauses that you cannot use a semicolon for. Here’s an example:

The wizard stirred the mixture, and it immediately changed color.

Strictly speaking, you can just use a semicolon here if you remove the comma and “and,” making the sentence read:

The wizard stirred the mixture; it immediately changed color.

That doesn’t look quite as good, so you use the comma and conjunction to make it sound better. Remember, though, that both sides of the sentence should also be complete sentences. The only reason you would connect them into a single unit is because, while they can stand on their own, they are better served as one.

4. On either side of superlatives or parenthetical asides.

This one is pretty straightforward. You use the commas to separate information that is given in a sentence that is related, but not, in the strictest sense, necessary. For example:

Dumah, the most powerful sorcerer in Tragon, would soon be cast down by the wizard’s conjuration. 

The phrase “the most powerful sorcerer in Tragon” can actually be removed from the sentence completely, and the remaining words would still make sense. Remember, this rule is for elements of a sentence that add to its meaning, but are still removable.

5. After an introductory phrase.

An introductory phrase is exactly what it sounds like; a phrase that introduces something. This tends to be some kind of description, much like the parenthetical aside used in the example above. For example:

One hand raised in triumph, the wizard released the magical energy necessary to conclude his dark work.

Again, this rule only applies if you can remove the separate element and still leave a complete sentence.

6. To reduce or avoid confusion.

Technically speaking, you don’t need to include a comma in the following sentence:

Inside, the energy swirled in a raging tempest that threatened to consume the wizard.

But without it, you have:

Inside the energy swirled in a raging tempest that threatened to consume the wizard.

The first one makes it clear that the energy is inside the wizard. Without the comma, that can still be gleaned, but it at first looks like we’re talking about something inside the energy itself. It’s better to use a comma here to avoid any confusion on the part of the reader. Remember, your goal is to communicate your thoughts clearly when you write.

7. Before a phrase that is designed to contrast. 

This is when you throw a literary change-up, and begin a sentence by introducing an element and end it by comparing it to something it isn’t. Confused? Look at this example:

Dumah was powerful, not omniscient. 


It was his intellect, not his strength, that failed him in the end.

Any time you add an element that contrasts the subject, you should add a comma both before and after it, unless the sentence ends with the contrast.


Those are the basic rules for comma usage. Let me leave you with some general advice.

1. Remember that commas are designed to separate things, not really to connect them. Even when independent clauses are connected with commas, it’s actually the conjunction that brings them together. If you want to connect two ideas with punctuation, that’s what semicolons are for.

2. Don’t overuse commas. I find that you tend to use them more often than ending punctuation; on average, I use about 1.2 commas per sentence. This is based on both prose and academic writing, however. If you find that your ratio is creeping up, you’re using too many commas. Remember that you don’t need to put a comma in every place you would take a natural break in a sentence. The spoken word and the written word are different. So when people tell you to just read a sentence out loud to find the commas, they’re not necessarily giving you the best advice. Sometimes, you just don’t need one.

3. Don’t underuse commas. They serve a purpose! Use them for the purposes necessary. A paper without commas would be frustrating to read. Learn the times and places to use them, and go from there.

4. The above rules do not cover every time you would put in a comma. These are just the most common examples I could think of. Unfortunately, there aren’t enough hard and fast rules to apply to every possible sequence of words, so naturally there will be some gaps. When in doubt, check the style guide of whatever format you’re using, be it APA, MLA, Chicago or what have you.

5. Microsoft Word’s grammar check sucksDo not trust it to pick up on your comma errors. It can catch some bad ones from time to time, but I’ve had errors slip through with no squiggly green line to warn me. You really do need to learn the rules.

Comments? Questions? Leave a comment, and I’ll get back to you when I can.

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