Commas serve two main functions: separating items in a list and separating independent clauses. Whether you put a comma before “and” depends on the situation.
Putting a comma before and in a list is generally optional, though style guides have different rules on this.
In general, you should always put a comma before and if it’s between two independent clauses (also thought of as statements), which I’ll discuss below.
Use a comma before “and” in lists of three or more — In lists of three or more, you can use a comma before and, depending on your style guide. For example:
The dogs were big, fluffy, energetic, and dumb.
Use a comma before “and” between independent clauses — Use a comma before and if the and is between independent clauses (phrases that could stand on their own as sentences). For example:
I like to pet the dogs, and I like to take them to the park.
When to Use Commas before “And” in Lists
Lists of Two
When you’re naming two things, do not use a comma before and. For example:
Correct: I went to the store for milk and bread.
Incorrect: I went to the store for milk, and bread.
Lists of Three or More — The Oxford Comma
Many folks get riled up about the serial comma or so-called “Oxford comma,” the comma that is placed before and in a list of three or more. It’s even been the subject of legal cases.
Here’s what it is: When you’re naming three or more things, put a comma before the final and.
I went to the store for eggs, milk, and bread.
Different style guides have different rules on the subject. The Associated Press Style Book does not use the serial comma, whereas the MLA Style Book does. I’m a proponent of it, and it’s our default here at EditorNinja.
Why? Because it can clear up confusion. Let’s look at an example made famous by the internet:
With serial comma: We invited the strippers, JFK, and Stalin.
Without serial comma: We invited the strippers, JFK and Stalin.
See the difference? The first sentence lists those invited: the strippers, and JFK, and Stalin. The second sentence, however, seems to tell us who the strippers are — JFK and Stalin.
Just use the serial comma, folks.
When to Use Commas before “And” with Independent Clauses
Use a Comma with Independent Clauses
Use a comma before and to separate two independent clauses. What’s an independent clause? It is a clause (a phrase or a part of a sentence) that could stand on its own as a sentence.
The kids went to the movies, and the parents stayed in.
Note that the clauses “the kids went to the movies” and “the parents stayed in” could be two complete sentences, so we add a comma before and.
The pitcher threw the ball, and the batter hit it.
Above, the two phrases could each be sentences on their own — they’re independent clauses, so the “and” needs a comma before it.
Don’t Use a Comma with a Dependent Clause
If, however, the second phrase is a dependent clause, we would not use a comma. For example:
Correct: The pitcher threw the ball and fell off the mound.
Incorrect: The pitcher threw the ball, and fell off the mound.
How do we know? Well, look at the phrase “fell off the mound.” It can’t be its own sentence (it has no subject), so it’s a dependent clause.
Some More Examples
Two independent clauses call for a comma before and:
Correct: I walked to the store, and I fell on the sidewalk.
Incorrect: I walked to the store and I fell on the sidewalk.
A second, dependent clause means no comma:
Correct: I walked to the store and fell on the sidewalk.
Incorrect: I walked to the store, and fell on the sidewalk.
(“Fell on the sidewalk” is dependent because it lacks a subject.)
If you have trouble remembering if you should use a comma or not, remember that “dependent” starts with d, as in don’t — don’t use a comma. This trick is called a mnemonic device. Learn more about mnemonics in this article.
Lists and Clauses — the Uses of the Comma
To sum up, don’t put a comma before and if there are only two items. Do put one before and in a list of three or more if it’s accepted by your style guide. (It never hurts to check with your publisher, editor, or professor.)
Do use a comma before and between two independent clauses — don’t if one of the clauses is dependent.
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