Know when to use this multipurpose piece of punctuation – and, just as important, when not to use it. Cut through the red tape of rules to understand why the comma exists and how it clarifies your meaning.
Commas should serve as signposts to clarify a writer’s meaning, not as a source of confusion. Nevertheless, problems arise—perhaps because commas are used in more frequently and in more varied ways than other marks of punctuation. But the fact is that the rules do make sense and are easy to master if you heed the following guidelines:
A. When commas are required:
1. To follow introductory words and word groups:
Fortunately, we were able to repair the item.
Yes, I can easily handle your order.
To tell you the truth, I am extremely annoyed.
If it rains, we’ll cancel the outing.
Note: Short or common introductory words don’t require the comma: thus, once, yesterday.
2, To divide independent ideas that have a connecting word like and or but:
Janet was not offered a job, but she was given a volunteer internship with the firm.
Note: Very short ideas do not require a comma: It rained and we left.
3. To indicate nonessential words or groups of words that add something to a sentence but do not affect meaning.
We are, shall we say, in a state of flux.
The manager, a long-time employee, has made valuable contributions to the company.
My uncle, who is a veteran, is a pilot.
“The Necklace,” which I read recently, is a moving story.
My mother, Sally Jones, is the CEO of a company.
(You can have only one mother so she is clearly identified; thus Sally Jones simply adds information.)
4. To separate dialogue:
He said, “We’re undertaking a new project.”
Note: With other quoted material, use as required.
As a “star performer,” I earned a bonus.
(Comma goes inside closing quotation mark.)
5. To divide adjectives of equal weight before a noun and to divide items in a series:
What a poignant, uplifting film!
I’ve worked in Boston, Chicago and Houston.
Note: No comma is needed before the final and unless confusion could result.
6. To show omission
Yesterday six people called in sick; today, two.
(Today six people called in sick.)
B. When sentences need commas for clarity:
1. To tell reader when to pause:
Confusing: The day after he arrived by train.
Clear: The day after, he arrived by train.
Confusing: Answer questions #1 and #2 or #3.
Clear: Answer questions #1, and #2 or #3.
2. To clarify intended meaning.
Be sure the message you intend is the one that’s delivered. The following sentences are both correct—but what a difference!
Anna, claimed Hank, planned the murder.
(With commas, Anna is the alleged criminal.)
Anna claimed Hank planned the murder.
(Without commas, the allegation shifts to Hank.)
C. When commas are simply practical:
1. After salutation in a social letter: Dear Al,
2. With repeated words: Whatever is, is best.
3. In date, between day and year: May 15, 2004
4. In numbers of 5 or more digits: < 10,000
5. Between city and state (but not state from zip code):
Lewiston, ME 04240
6. With most abbreviated titles after the name
John Jones, Ph.D., spoke at the meeting.
Note: Don’t use comma with Jr. after the name.
D. When commas are not required:
1. Don’t divide a subject and verb or verb and complement. Delete commas.
Wrong: An employee who is late, will lose pay.
Right: An employee who is late will lose pay.
Wrong: The mailing failed to produce, the desired results.
Right: The mailing failed to produce the desired results.
2. Don’t divide adjectives of unequal weight.
Wrong: We had an exciting, summer vacation.
Right: We had an exciting summer vacation.
Note: If you can’t put the word and logically between them (exciting and
summer vacation), they are unequal. Delete comma.
3. Don’t use commas to divide independent ideas if there is no connector.
Use a semicolon instead.
Wrong: It is nearly five, the office id closing.
Right: It is nearly five; the office is closing.
4. Don’t use commas with essential material.
Information is essential if the sentence, when without it, doesn’t seem
logical or complete.
The man who aided my career is my uncle.
(Underlined material identifies which man.)
My cousin Ed is a company treasurer.
(One can have many cousins so the name Ed is necessary to identify
The book that I read last week is a best seller.
(Underlined information identifies which book.)
Note: When the explanatory words begin with the word that, the material is always essential.
That, in a nutshell, is the story of commas. Simply follow the rules, making common sense exceptions to avoid confusion. By doing so, you’ll use commas accurately, comfortably—and confidently!