Anthony R. Garcia
The comma is the Swiss Army knife of punctuation marks. Its versatility comes in handy when crafting sentences, but first, you must understand its different functions.
Here are 11 common uses:
1. Use a comma to join two independent clauses with a coordinating conjunction
Example: Johnny rushed to the top of the hill, but he was too late to see the fireworks.
Example: The moon was out, and the coyotes were looking for food.
2. Use a comma after an introductory phrase or clause
Example: At the end of the game, the two coaches shook hands.
Example: Driving to work, Greg saw an abandoned house he had never noticed.
When the introductory phrase is short (not more than four words as a rule of thumb), a comma may not be necessary.
Example: From my room I saw her approaching my house.
But in some cases even a short introductory phrase should be followed by a comma to prevent miscues.
Example: After I wake up Gabriel and I are going to the park.
For a moment, it seems as though the subject plans to wake Gabriel from his sleep, but that’s not the case:
Revised: After I wake up, Gabriel and I are going to the park.
Inserting the comma prevents Gabriel from being construed as a direct object, when it is actually part of a compound subject.
3. Use a comma after introductory and conjunctive adverbs
Example: Thankfully, we have more time than we thought.
Example: Contrary to popular belief, Thomas Edison did not invent the light bulb.
Example: We live in strange times; however, I believe we will find our way.
4. Use a comma to set off nonessential phrases and clauses
Example: I sometimes sit and think, in sobering moments, about the times we didn’t share.
Example: Greg drove his new car, which his father had just bought for him, right into the bushes.
In these examples, the commas set off information that is not essential to the meaning of the sentence.
5. Use a comma to separate items in a series
Example: My favorite colors are pink, purple, and blue.
Example: The crooked trees, the quiet wind, and the jaundiced moonlight made me feel uneasy during what was supposed to be a romantic evening.
6. Use a comma between adjectives that modify a noun when “and” could appear between them and their order could be changed without changing the meaning of the sentence.
Example: He grabbed my wrist with his cold, sweaty hand.
The comma is appropriate in the above sentence because you can place “and” between the adjectives (…his cold and sweaty hand.) and you can switch the order without affecting the meaning (…his sweaty, cold hand.)
Example: I live in the oldest, ugliest, loudest part of town.
7. Use a comma to set off dialogue.
Example: After the movie, she turned to me and said, “Tonight has been wonderful,” though the mumbling crowd made it hard to hear.
Example: “I don’t much care for wheat,” said my mother as I lowered her plate to the table.
8. Use a comma to separate full dates and addresses
Example: I was born on January 25, 1972.
Example: I no longer live at 5555 N 125th Ave., Phoenix, AZ 85001
9. Use a comma to separate thousands, written numerically
Example: This artifact dates back approximately 3,000 years.
Example: My bonus this year was exactly $10,141. Wait, I wrote that wrong; it’s actually $1,141.
10. Use a comma when addressing someone by name or nickname.
Example: Please stop talking, Donald.
Example: Just give me the two dollars, cheapskate.
11. Use a comma to introduce a direct question that is part of another sentence
Example: I always ask myself, Who’s in charge here?
Example: It was on that beach your father popped the question, What do you think about a divorce?
This is a brief overview, based mostly on the Chicago Manuel of Style. I recommend consulting your preferred (or required) style guide when questions of comma usage arise.