CGTC FAQs: Academic Support

To understand how and when to use commas, one must first understand sentence structure and what the difference is between a dependent and independent clause. While the examples I give are my own, all this information is pulled straight from PurdueOwl, an excellent resource from Purdue University on all things punctuation and citation.

Independent clause: a clause that has a subject and a verb and can stand alone; a complete sentence.

Dependent clause: a clause that has a subject and a verb but cannot stand alone; an incomplete sentence.

Now that you know the difference, let's begin!

Commas are most commonly used to join two independent clauses and a coordinating conjunction (and, but, or, for, nor, so).

~ Example: I really want to go to the park today, but the forecast is predicting rain.

Commas can also be used after an introductory phrase, prepositional phrase, or dependent clause.

~ Example: Because it began to rain, I stayed home and built a pillow fort.

Commas are perhaps best known for their use in separating elements in a series. Although there is no set rule that requires a comma before the last item in a series, it seems to be a general academic convention to include it.

~ Example: I used the couch cushions, the big blanket, and all the pillows from my bed.

Commas are also used to separate nonessential elements from a sentence. This is information that isn't needed for the sentence to make sense, but is nice to know/provides good detail.

~ Example: The big blanket, the one we use for movie nights, was perfect for the roof of my pillow fort.

Commas separate coordinate adjectives (adjectives that are equal and reversible) and transitional elements (however, for example, in conclusion, etc.)

~ Example. The sturdy, fuzzy couch cushions made for really good walls. The pillows from my bed, however, were too floppy.

Commas are also used in quoted words such as dialogue. I'll go into more detail about dialogue in another FAQ, but suffice to say, they are used when the quoted words are split up by narration.

~ Example: "Yes, mom," I said, asking if I could borrow some of her and dad's pillows, "I'll bring them back when I'm done."

Finally, Commas are used in dates, numbers, titles, and to separate city names from states.

~ Example: On June 11, 2024 in Milledgeville, Georgia, I made a pillow fort in my living room. I sold it to King Stuffington, Lord of the Stuffed Ones who reside in the kingdom of Blanket Upon Bed, for 50,000 imaginary cotton-ball bucks!

One final note, Avoid comma splices (two independent clauses joined only by a comma). Instead, separate the clauses with a period, with a comma followed by a coordinating conjunction, or with a semicolon, which we'll learn more about in another FAQ.