- Use commas to separate elements in a series, but do not put a comma before the conjunction in a simple series.
Example: The flag is red, white, and blue. He would nominate Tom, Dick, or Harry.
- Use a comma also before the concluding conjunction in a complex series of phrases.
Example: The main points to consider are whether the athletes are skillful enough to compete, whether they have the stamina to endure the training, and whether they have the proper mental attitude.
- With equal adjectives: Use commas to separate a series of adjectives equal in rank. If the commas could be replaced by the word “and” without changing the meaning, the adjectives are equal: a thoughtful, precise manner; a dark, dangerous street.
- With salutation in correspondence: Although AP style recommends a colon after the salutation in business or formal letters, since our tone is friendly and familiar, we use a comma.
Example: “Hi, Name.” “Good afternoon, Name.”
- With conjunctions: When a conjunction such as “and,” “but,” or “for” links two clauses that could stand alone as separate sentences, use a comma before the conjunction in most cases.
Example: She was glad she had looked, for a man was approaching the house.
- Introducing direct quotes: Use a comma to introduce a complete one-sentence quotation within a paragraph.
Example: Wallace said, “She spent six months in Argentina and came back speaking English with a Spanish accent.”
- Before attribution: Use a comma instead of a period at the end of a quote that is followed by attribution.
Example: “Swipe your card,” the banker suggested.
- Using “that” or “which”: Do put a comma before “which.” Do not put a comma before “that.”
Example 1: Upcoming payment amount, which may include principle, interest, and escrow.
Example 2: Balance excluding transactions that are in process or pending.
- With hometowns and ages: Use a comma to set off an individual’s hometown when it is placed alongside a name (whether “of” is used or not). If an individual’s age is used, set it off by commas.
Example 1: Tom Richards, San Francisco, California, and Brian Findlay, New York, New York, were there.
Example 2: Brian Findlay, 48, New York, New York, was present.
- Names of states and nations used with city names
Example: His journey will take him from Dublin, Ireland, to Fargo, North Dakota, and back. The Selma, Alabama, group saw the governor.
Example: Yes, I will be there.
Example: Name, I am running late. No, sir, I did not yet make the transfer.
- Separating similar words: Use a comma to separate duplicated words that otherwise would be confusing.
Example: What the problem is, is not clear.
- Placement with quotes: Commas always go inside quotation marks.
- With full dates: When a phrase refers to a month, day, and year, set off the year with commas.
Example: February 14, 2023, is the target date.
- Nonessential phrase: A nonessential phrase can be deleted without changing the meaning of a sentence.
- Essential phrase: This type of phrase is necessary for the sentence to make sense. Do not set an essential phrase off from the rest of a sentence by commas.
Example 1: We saw the award-winning movie Titanic. (No comma, because many movies have won awards, and without the name of the movie the reader would not know which movie was meant.)
Example 2: They ate dinner with their daughter Julie and her husband, David. (Julie has only one husband. If the phrase read “and her husband David,” it would suggest that she had more than one husband.)
Example 3: The company chairman, Bill Gates, spoke. (In context, only one person could be meant.)