The comma. It’s a small, seemingly inconsequential little piece of punctuation, but oh, how important it is. According to the Chicago Manual of Style 16th Edition, “The comma, aside from its technical uses in mathematical, bibliographical, and other contexts, indicates the smallest break in sentence structure.” But contrary to popular belief, which often sees its use as a bit arbitrary, there are some hard and fast rules for using commas.
This topic might very well be the one thing writers struggle with the most, so here’s the scoop on when to use those little guys.
Use a comma or commas in:
- Series of items
He invited Mary, Susan, Steve, and Mark to the party.
- Compound sentence
When you have two independent clauses (both parts of the sentence could stand on its own) joined by a conjunction (for, and, nor, but, or, yet, so. An acronym to help you remember is FANBOYS), a comma is used to connect the clauses.
She wanted to watch Star Wars, but he wanted to watch something else.
independent clause independent clause
- Compound predicate (One subject governing two verbs)
Use a comma only if needed for emphasis or clarity.
Mary ate candy and pizza and went to bed with a stomachache.
But you might use it rarely for emphasis like this:
Mary ate candy and pizza, and went to bed sick.
- Commas with a dependent clause (One clause of the sentence depends on the independent clause, the one that can stand alone.)
If Billy does not get his grades up, he will not graduate.
dependent clause independent clause
- Introductory elements
Use a comma with an introductory phrase.
Before getting dressed, he took a shower.
Unfortunately, he was late.
- Coordinate adjectives (Two adjectives that carry the same weight in describing the noun.)
She was a faithful, sincere friend.
Questions for deciding whether adjectives are coordinate:
- Can the adjectives be reversed without changing the meaning?
She was a sincere, faithful friend. Yes.
- Can the word and be inserted between the adjectives?
She was a faithful and sincere friend. Yes.
If yes to both, the adjectives are coordinate, and a comma should be used.
- Phrases of contrast
The book, not the movie, tells the real story.
- Yes and no
Yes, you can go the dance.
No, you may not go out now.
Well, I guess we could go to dinner early.
Oh, I had no idea!
- Parenthetical elements/nonessential elements
A nonessential element is something that adds information to the sentence but isn’t essential to its understanding.
Jim, surprisingly, won the race.
- Comma with relative clauses (which)
Relative clauses act like an adjective and give more information about a noun. These clauses take “which” (nonrestrictive) and “that” (restrictive).
Her home, which was in California, burned down when she was five.
“That” signifies a restrictive clause, which means the information is essential to the meaning of the sentence and does not take a comma.
Her home that burned down was in California.
- Direct address
Hey, Mary, will hand me that book?
- Direct quotation
“I don’t like this movie,” Mary said.
- Addresses, geographical locations
Her hometown is Sedona, Arizona, near the Poconino Forest.
Her home is at 111 Paddington Drive, Kyle, Texas 78640, near Austin.
September 11, 2001, was a terrible day in US history.