Rule #1
Use a comma before any coordinating conjunction (for, and, nor, but, or, yet, so) that
links two independent clauses.
Examples: I went running, and I saw a duck.
We wanted to go to the park, but we were too tired.
Side note - An independent clause is a unit of grammatical organization that includes both
a subject and verb and can stand on its own as a sentence.
Rule #2
Use a comma after a dependent clause that starts a sentence.
Examples: When I went running, I saw a duck.
If we go to the movies, we will get popcorn.
Side note - Commas always follow these clauses at the start of a sentence. If a dependent
clause ends the sentence, however, it no longer requires a comma.
I saw a duck when I was running.
We will get popcorn if we go to the movies.
Rule #3
Use commas to offset appositives from the rest of the sentence.
Examples: A mallard, a kind of duck, attacked me.
The insect, a large cockroach with hairy legs, is crawling across the kitchen table.
Side note – An appositive is a noun or noun phrase that renames another noun right beside
it. Appositives can be short or long.
Rule #4
Use commas to separate items in a series.
Examples: My sister went shopping for milk, cookies, apple juice, and bread.
The athletes warmed up, ran for a mile, and rode their bicycles for twenty minutes.
Rule #5
Use a comma after introductory adverbs and transitional words/phrases.
Examples: Finally, I went running.
Unsurprisingly, I saw a bear while hiking.
Next, the class went to the library.
In conclusion, the party was not that good.
Rule #6
A comma is used after a word like yes, no, or well when it appears at the beginning of a
sentence.
Examples: Yes, that flight will arrive on time.
No, I don’t think it is going to rain.
Well, he certainly surprised me.
Rule #7
Use a comma before a conjunction that joins independent clauses in a compound sentence.
Examples: I was going to play outside, but the sky looks very gloomy.
I like to watch movies, and she likes to read books.
Are we going to go biking, or are we going to go swimming?
Rule #8
A comma is used to separate the words of a direct quotation from other words in the
sentence.
Examples: If attribution comes before the quote, place the comma outside the quotation
marks.
The runner said, "I saw a duck.” If attribution comes after the quote, put the comma inside
the quotation marks. "I saw a duck," said the runner.
Rule #9
Use a comma when directly addressing someone or something in a sentence.
Examples: My editor asked, "Christina, is that article ready yet?“
“Lisa, answer the phone,” mom said.
Rule #10
Use a comma between two adjectives that modify the same noun.
Examples: I saw the big, cute duck when I went running.
She wore a bright, pretty dress to the dance.
Side note - Only coordinate adjectives require a comma between them. Two adjectives are
coordinate if you can answer yes to both of these questions:
1. Does the sentence still make sense if you reverse the order of the words?
2. Does the sentence still make sense if you insert "and" between the words?
Sentences with non-coordinate adjectives, however, don't require a comma.
For example, I lay under the powerful summer sun.
Rule #11
A comma is used to separate the name of a city from the name of the state or country. A
comma also follows the state or country name when other words follow in the sentence.
Examples: Los Angeles, California
Denver, Colorado
The zoo in San Diego, California, is a popular tourist attraction.
We will arrive in Denver, Colorado, on Thursday or Friday.
Rule #12
A comma is used to separate the day and the month from the year in a date. A comma also
follows the year when other words follow in the sentence.
Examples: April 6, 1957
July 20, 2015
Her vacation began May 10, 2018, and lasted three weeks.
School ends of June 15, 2010, and starts again on August 28, 2010.
Rule #13
Use commas before every sequence of three numbers when writing a number larger than
999. (Two exceptions are writing years and house numbers.)
Examples: 10,000
13,245,167
Rule #14
A comma is used after the greeting and the closing in a friendly letter.
Examples: Dear Andrew,
Dear mom,
Sincerely yours,
Your friend, Love,
