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Three Common Grammatical Mistakes: Commas

Commas are a tricky beast for everyone. There are so many uses for the comma, and many times it feels like you’re just supposed to use your best judgment. But too often those pauses become unnatural and cumbersome, or, if you decide to be sparse, your readers feel like they’re galloping through a sentence. How do you find a balance?

Again, rules are key here, and today I’m going to tell you three rules about commas that I’ve seen misused a lot recently.

Before we begin, here are some ground rules. Excuse me if I’m being patronizing, but I want to make sure we’re all on the same page.

A clause is a phrase or set of words that all go together. For example, “I went to the store” is all one sentence, but it is also all one clause, an independent. “Without her knowledge of psychology”  is also a clause, but it’s only part of a sentence.

A complete sentence or independent clause is one that can stand on its own. Every sentence or independent clause requires a subject and verb. That’s it. “I went.” “You ate.” “That is.” These are all legitimate sentences. Unfortunately, sometimes constructing a complete sentence is harder than it sounds, as you might see below.

All right, now let’s begin.

1. Oxford Commas

A lot of people don’t appreciate Oxford commas anymore, and this makes me sad because they make so much sense to me. I like it because of its uniformity to the rest of the list. Others think it just clutters up the sentence.  Many stylebooks don’t call for Oxford commas, but Chicago Manual of Style does, so if you’re writing a novel, make sure to include them.

What are Oxford Commas?

When you have a list of three or more items, the Oxford comma is the one right before the and of the last item. For example, “I went to the store and bought grapes, juice, and soda.” The red comma is the one in question. Here’s another reason why I think Oxford commas are important. If you look at the image I linked in the previous sentence, you’ll see that without a comma, the two last items can be run together. And yes, sometimes this is necessary.

2. Independent vs. Dependent Clauses

So the rule of thumb here is that if the clause is dependent, there is no comma. If the clause is independent, add the comma. I think the easiest way to remember is that independent clauses want to have nothing to do with the first part of the sentence, because they’re so independent, so they need a comma to separate the two. I think a hundred years ago the rule was different, becuase I saw the exact opposite when I read Jane Eyre.

What is a dependent clause?

This is where it gets difficult. Let’s consider the two sentences below.

a. I went to the store, and I bought a pair of shoes.

b. I went to the store and bought a pair of shoes.

These two sentences are nearly identical except for one thing. In sentence A, the second clause, “and I bought a pair of shoes,” has its own subject, I. In sentence B, the second clause borrows the subject from the first clause (also I). Sentence A has an independent clause because of its seperate subject. Therefore, it requires a comma.

Sentence B is dependent because it can’t stand on its own. “Bought a pair of shoes,” while perhaps an acceptable facebook status, doesn’t qualify as a complete sentence. Therefore it depends on the first part of the sentence, “I went to the store,” to sustain it by lending it its subject.

3. Introductory Phrases

Most of us have a penchant for setting off every single introductory phrase with a comma. However, most of the time this leads to unnecessary pauses when really the phrase can just flow into the sentence. The longer the introductory phrase, the more likely you are to need a comma after it. The rule I follow is that if there are four or more words in your introductory phrase, add a comma. Otherwise, leave it alone.

What is an introductory phrase?

Well, it’s basically what it sounds like. It’s a phrase that is at the beginning of  your sentence but isn’t the main clause because it doesn’t contain your sentence or verb.

Before I went to the store, I put on my shoes.

The first six words in this sentence are an introductory phrase. “I put” is the actual sentence. “Before I went to the store” just qualifies when I put. Becuase it was longer than four words, I added a comma.

After lunch I went to the store.

Again, “after lunch,” denotes the setting of the main phrase. However, since it’s so short, you don’t need to put a comma after it. Adding a comma wouldn’t change the meaning of the sentence, but if you’re going for a sparse, clean look with easy readability, I suggest leaving the comma out.


Well, I hope I haven’t overwhelmed you too much for one week. Come back next month, and I’ll have some more grammatical tips for you. Happy writing!

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