The Top 5 Comma Rules for Clear Writing
You may have been taught that commas go “wherever you pause,” but that advice often leads to confusion. And in fact, it’s one of the most misleading grammar tips you could follow. The reality is that commas follow specific grammatical guidelines that help clarify sentence meaning and structure. Below are five essential rules that will help you write more clearly and avoid common mistakes.
Rule One: Use a comma to separate each item in a list.
I’m inviting Jake, Lisa, Ronnie, and Kyle to my dinner party.
When you go to the store, please pick up eggs, butter, and sugar.
We studied cause and effect, fact and opinion, and compare and contrast.
Notice how a comma is placed before the final “and” in the first two examples. This is known as the Oxford comma, and it is used to maintain clarity, letting the reader know that each item is its own separate entity. If I write, I like to read young adult, science fiction and fantasy and forgo the last comma, I’m saying that I like to read young-adult science fiction and young-adult fantasy. However, if I write, I like to read young adult, science fiction, and fantasy, I’m saying that I like to read three separate genres: young adult, science fiction (of any age), and fantasy (of any age).
In the third example, there is not a comma before each “and.” This is because the example shows a list of groupings. “Cause and effect” go together, and so does “fact and opinion” and “compare and contrast.”
Rule Two: Place a comma after introductory phrases and clauses.
Introductory phrases and clauses set up the rest of the sentence but cannot stand alone. The difference is that an introductory clause has a subject and verb, while an introductory phrase does not.
Common introductory phrases include expressions like “first of all,” “however,” “therefore,” “furthermore,” etc.
Introductory clauses, on the other hand, often begin with words such as “after,” “although,” “as,” “because,” “before,” “if,” “since,” “though,” “until,” “unless,” “when,” etc.
For example,
To put it simply, pets are not allowed in this hotel.
However, the hotel down the street allows small dogs.
Until the sun sets, we will work in the yard.
The third sentence is an example of an introductory clause. Notice how the comma is placed after the entire clause (not just although).
*Hint: you can tell you have an introductory clause when you can flip the sentence and it still makes sense. We will work in the yard until the sun sets. The sentence still works in this order.
Rule Three: Place a comma before a coordinating conjunction joining two independent clauses.
Need help remembering coordinating conjunctions? Just remember the FANBOYS: for, and, nor, but, or, yet, so.
I need to go to the store, but I really don’t want to.
My essay is due tonight, yet I don’t feel motivated to start writing.
Help me clean the house today, and I promise I’ll never ask again.
Remember that an independent clause is the same thing as a complete sentence. In other words, it can stand on its own. I need to go to the store could be its own sentence, and so could I really don’t want to.
Rule Four: Separate nonessential information with a comma (or commas).
Dr. Paul, a professor of psychology, studied the correlation between cell phone usage and poor sleep quality.
My brother, a skilled drummer, plays in a local band.
We went hiking in the grand canyon, a place we’ve never been before.
Notice how the phrases offset by commas could be removed from the sentences without impacting the meaning.
Dr. Paul studied the correlation between cell phone usage and poor sleep quality.
It’s helpful to know that Dr. Paul is a professor of psychology, or that my brother is a skilled drummer, but it’s not essential.
*In cases where the information is essential, leave the commas out: Students who study regularly tend to do better on exams. The phrase who study regularly directly impacts the outcome of the sentence.
Rule Five: Separate equal coordinate adjectives with a comma.
Coordinate adjectives are two or more adjectives that describe the same noun. When these adjectives are equal (i.e., you can switch the order or add “and” in between them), separate them with a comma.
It was a long, tiring day.
She adopted a small, fluffy puppy.
He wore a bright red shirt.
In the first two examples, both of the adjectives describe the same noun. In both cases, the order of the adjectives doesn’t matter (long, tiring or tiring, long and small, fluffy or fluffy, small), and in both cases, the comma could be replaced with “and” (long and tiring and small and fluffy).
However, in the third example, bright describes red, and red describes shirt; therefore, we leave the comma out. In other words, every word is exactly where it needs to be in order for the sentence to make sense.
As you can see, commas do a lot more than signal a pause—they are essential to sentence clarity. By learning these five rules, you are taking a pivotal step towards writing that is polished, professional, and easy to understand.
