Commas are one of the most misused and abused punctuation marks out there. I think part of this is because we’re taught in elementary school that they indicate a pause. This is correct, but people have a tendency to take this a bit too far, including commas whenever and wherever they would pause when speaking. It’s a good enough rule of thumb to get by in a pinch, but you run the risk of overusing them when putting it to practice.
So let’s take a closer look at the comma today. When is it needed, and when is it extra?
Use a comma to join simple sentences into a compound sentence.
You might remember us touching on this first one when we discussed compound sentences. When you connect two sentences using a conjunction such as and, but, or so, you must place a comma before the conjunction.
Tommy ran across the lawn, and he climbed a tree.
Sarah loved the pretty lace, but she didn’t like the dress it was on.
Think of the comma in this case like an interior wall with the independent clauses being separate rooms. Both rooms are part of the same building, but the wall indicates they are different rooms. Without the comma, the building would just be one huge room whose ceiling might collapse from lack of support.
Use commas to separate items in a list.
When you are writing a list of three or more items, without placing a conjunction between them, you must place a comma between each item, including the last two.
I realize there is a point of contention on this. AP style, the style in which newspaper and magazine articles are usually written, drops this final comma before the “and” connecting the last item in the series. This was done to save valuable printing space, and it eventually became so ubiquitous, the inclusion of this series or Oxford comma is often seen as “unnecessary.” However, what is done in AP style isn’t true for every style of writing, especially the formal writing done for school courses.
Outside of writing for print with a set number of pages, I’m a big believer in the Oxford comma, and I’ll tell you why. It changes the way a sentence reads. Take this rather silly illustration that’s floated around the Internet for years.
This morning I had eggs, toast, and orange juice for breakfast.
This morning I had eggs, toast and orange juice for breakfast.
In the first sentence, it’s clear all three things are separate items. In the second sentence, whether you picture the toast and orange juice as separate items or a piece of toast soaked in orange juice depends on how the individual reads it. The Oxford comma just makes things clearer, and a writer’s first duty is express their points in a clear way.
If you decide to list items with a conjunction between them for emphasis, a comma is no longer needed.
Tom still had to make his bed and wash his clothes and dust his room before he could go out to play.
When used this way, the added ands imply Tom’s begrudging attitude toward doing his chores. While an effective tool for writing fiction, this isn’t a technique I’d try for an essay or other formal school paper, and it’s certainly not one you’d use for a newspaper article. When in doubt, just use the commas.
Use a comma to set off an introductory clause.
Here’s something else we talked about earlier. Remember the lesson on complex sentences? Whenever you include a dependent clause at the beginning of a sentence, use a comma to separate it from the independent clause. I just used this rule in the sentence before this, but I’ll give you another couple of examples.
Running to the house, Mary waved and wished her friends a good evening.
While cleaning his room, Tom found the pair of rollerblades he lost two weeks ago.
Use commas to separate parenthetical clauses from the rest of the sentence.
We talked about when to use parentheses in our last lesson. Remember how they could be used to separate a phrase that adds to a sentence but isn’t necessary to understand it? Well, you can do the same thing with commas.
Aden took his son, Tom, to the skate park after he finished his chores.
Sarah took the trim, a delicate lace, off of the dress.
Use commas to separate dates from their years and to set off the states or country a city is in.
When writing a full date in a sentence, make sure to place a comma between the date and the year.
A deadly rash of tornadoes struck the southeastern United States on April 27, 2011.
Similarly, when a city name is followed by the state or country it’s in, the name of that state or country should be treated like a parenthetical clause.
The couple went to Miami, Florida, for their honeymoon.
Con Kasterborous is held in Huntsville, Alabama, every summer.
Use a comma to set off quoted elements.
Please see lesson on quotations for more on this point.
Use commas to separate out contrasting phrases.
I asked for vanilla ice cream, not chocolate.
A rat’s intelligence makes them an easily trainable, but mischievous, pet.
In the examples above, the clause separated out with commas contrasts to the rest of the sentence. The commas not only add clarity to the sentence as a whole, but they serve to emphasize the difference between both points.
Use commas to separate coordinating adjectives.
When you’re feeling particularly descriptive and want to add several adjectives before the noun, you might need commas. This doesn’t work with every phrase, so ask yourself if you could put “and” between the adjectives. If you can and it still makes sense, use commas instead.
She climbed down into the dank, dark cellar to retrieve a jar of tomatoes.
The witch lived in a quaint little house made of candy.
He looked up at the huge, snarling, blood-thirsty dragon with his knees shaking inside his armor.
Use a comma to separate a person’s title if it’s listed after their name.
Here’s the same sentence written two ways. Notice when the comma is used and when it isn’t.
Mayor Rigsby said he signed the new bill yesterday.
Gregg Rigsby, Mayor of Appleford, said he signed the new bill yesterday.
You don’t need a comma when the title is used before the person’s name, but you need a comma before and after the title if it is placed after their name.
Don’t put a comma between a subject and its verb.
This one should be clear cut most of the time, but sometimes the subject of a sentence reads like an introductory clause with the subject at the end. When this happens, don’t use a comma. A true introductory clause should end before the sentence’s subject, not include it.
Here you have the basics of when and where to use commas. They are a common and essential part of the written English language, but please do be careful of overusing them, which is the usual problem.
If you have comments or questions, please leave them below. I try to answer each within twenty-four hours.
In addition to working as a freelance writer, A. B. England is a novelist, all around geek, avid crafter, and a homeschooling mother of two.
She is an autistic creator with a love of mythology, fantasy, and all flavors of science fiction.
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