The comma.

Ah, the comma. Of all the punctuation marks in English, this one is perhaps the most abused and misused. And it's no wonder. There are lots of rules about comma usage, and often the factors that determine whether you should use one are quite subtle. But fear not! Below, you'll find guidance for the trickiest comma questions.

What Is a Comma?

While a period ends a sentence, a comma indicates a smaller break. Some writers think of a comma as a soft pause—a punctuation mark that separates words, clauses, or ideas within a sentence.

Comma with Subjects and Verbs.

With few exceptions, a comma should not separate a subject from its verb.

Incorrect:
My friend Cleo is a wonderful singer.

Writers are often tempted to insert a comma between a subject and verb this way because speakers sometimes pause at that point in a sentence. But in writing, the comma only makes the sentence seem stilted.

Correct:
My friend Cleo is a wonderful singer.

Be especially careful with long or complex subjects:

Incorrect:
The things that cause me joy, may also cause me pain.

Correct:
The things that cause me joy may also cause me pain.

Incorrect:
Navigating through snow, sleet, wind, and darkness, is a miserable way to travel.

Correct:
Navigating through snow, sleet, wind, and darkness is a miserable way to travel.

Comma Between Two Nouns in a Compound Subject or Object.

Don't separate two nouns that appear together as a compound subject or compound object.

Incorrect:
Cleo, and her band will be playing at Dockside Diner next Friday.

Correct:
Cleo and her band will be playing at Dockside Diner next Friday.

Comma Between Two Nouns in a Compound Subject or Object

Don't separate two nouns that appear together as a compound subject or compound object.

Incorrect:
Cleo, and her band will be playing at Dockside Diner next Friday.

Correct:
Cleo and her band will be playing at Dockside Diner next Friday.

Incorrect:
Cleo will wear a sparkly red blazer, and high heels.

Correct:
Cleo will wear a sparkly red blazer and high heels.

When a subject or object is made up of two items and the second item is parenthetical, you can set off the second item with commas—one before it and one after it. But you don't need a comma when you're simply listing two items.

Comma Between Two Verbs in a Compound Predicate

You get a compound predicate when the subject of a sentence is doing more than one thing. In a compound predicate that contains two verbs, don't separate them with a comma.

Incorrect:
Cleo will sing, and play the banjo.

Correct:
Cleo will sing and play the banjo.

This mistake is most common when the predicate is made up of long verb phrases.

Incorrect:
I meant to buy tickets for Cleo's show, but ran out of time.

Correct:
I meant to buy tickets for Cleo's show but ran out of time.

Don't use a comma in compound predicates unless there is a chance of misreading:

Cleo spotted the man who entered the diner, and waved.
In the sentence above, you need the comma to make clear that it was Cleo who waved, not the man.

Comma Splices.

When you want to join two independent clauses, you need a conjunction or a semicolon. A comma alone isn't strong enough to join them. This kind of mistake is called a comma splice.

Incorrect:
We were out of milk, I went to the store.

You can fix a comma splice by adding a conjunction or changing the comma to a semicolon.

Correct:
We were out of milk, so I went to the store.

Correct:
We were out of milk; I went to the store.

Or, you can simply write the two independent clauses as separate sentences.

We were out of milk. I went to the store.

Comma Within a Comparison.

Don't use a comma before "than" when you're making a comparison.

Incorrect:
This box is lighter, than that box.

Correct:
This box is lighter than that box.

Incorrect:
Hardcover books are more expensive, than paperback books.

Correct:
Hardcover books are more expensive than paperback books.

Commas with Interrupters or Parenthetical Elements

Interrupters are little thoughts that pop up in the middle of a sentence to show emotion, tone, or emphasis. A parenthetical element is a phrase that adds extra information to the sentence but could be removed without changing the meaning of the sentence. Both interrupters and parenthetical elements should be set off with commas.

Incorrect:
The weather I was happy to see was beginning to clear.

Correct:
The weather, I was happy to see, was beginning to clear.

Incorrect:
Geoff's cooking skills if you can call them skills left something to be desired.

Correct:
Geoff's cooking skills, if you can call them skills, left something to be desired.

Incorrect:
It was sadly the last day of camp.

Correct:
It was, sadly, the last day of camp.

Incorrect:
Mary unlike Anne is very organized.

Correct:
Mary, unlike Anne, is very organized.