Robots love commas.

Commas aren’t some piece of punctuation meant to aggravate you. They can actually be used as rhetorical tools, meaning that you can use them to emphasize information. Commas can also help you add clarity to your writing so you don’t confuse your readers.

Commas separate, introduce, and show information. While comma rules aren’t completely rigid, there are some comma guidelines that you should be familiar with. Once you get to know these, you can begin to mess with them to suit your rhetorical needs.

HOW TO USE COMMAS

There are four cases when you should really use commas:

1. To separate clauses. Commas often separate an independent clause (a phrase that can stand alone as a sentence) from a dependent clause (a phrase that can’t stand alone).

• When the robot was first built, he didn’t have any legs.

2. To separate parenthetical phrases. Parenthetical phrases interrupt other phrases or clauses, and contain extra information that could be removed from the sentence without changing the sentence’s core meaning.

• The robot, which had no name, was created to guard and protect the Writing Center.

3. To separate introductory phrases. An introductory phrase is a phrase at the beginning of the sentence (usually a dependent clause) that provides background information for the main sentence.

• While the robot was painted silver, he had a heart of gold.

4. To balance two independent clauses (with a coordinating conjunction). Two independent clauses can be two separate sentences, or can be combined into one sentence using a comma and a coordinating conjunction (and, but, or, yet, for, nor, so).

• Students loved the robot, for he was kind and generous.
• The robot enjoyed getting to see the students, but he was always sad when the Writing Center closed for the night.
• The tutors realized how lonely the robot was becoming, so they built him a robot dog to keep him company.

HOW TO NOT USE COMMAS

Even though there is a lot of flexibility in what ways you can use commas, there are also cases when you should avoid using them:

1. Don’t separate the verb from its subject or its object.

• The robot, danced when no one was looking. → The robot danced when no one was looking. (The robot is the subject, danced is the verb.)
• The robot walked, his robot dog. → The robot walked his robot dog. (Walked is the verb, his robot dog is the object.)

2. Don’t use a comma between an adjective and a noun.

• The cardboard, robot was always eager to help students with their writing. → The cardboard robot was always eager to help students with their writing.

3. Don’t use a comma before the first item in a series.

• The robot likes, gummy worms, break dancing, and paper cranes. → The robot likes gummy worms, break dancing, and paper cranes.

4. Don’t use a comma after a coordinating conjunction.

• The robot was large yet, gentle. → The robot was large yet gentle. *OR* The robot was large, yet gentle.

Note: You can use a comma before the coordinating conjunction if you want, but you don’t have to, since the two clauses are not independent clauses. Whether or not you put a comma before the coordinating conjunction in cases like this will depend on how much you want to emphasize the piece after the conjunction.

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We hope this rundown of good and not-so-good uses of commas is helpful for you. If you have any more punctuation questions, feel free to stop by the Writing Center or schedule an appointment here.

We also hope that you’ll stop by and check out our new giant cardboard robot—he still needs a name and we would love your input!

—Annie and Sarah, peer tutors