Commas indicate pauses in sentences so readers can easily digest information and keep distinct ideas separate. Improper comma use can have the opposite effect; it can lead to garbled sentences that, although they may contain the correct information, don’t flow properly.

Comma Rule 1:
Use a comma when two sentences are joined with and, or, but, or nor.

When two complete sentences are joined with and, or, but, or nor, place a comma before the and, or, but, or nor. A sentence that has two or more verbs but does not have two complete sentences does not require a comma.

Comma Rule Examples

Incorrect:

  1. Modern technology makes counter-conventional management possible but the causality also works the other way.
  2. Others felt that technology development was important but it should not be our key purpose.
  3. Our aim is to contribute to our company’s success, and be responsive to our customers.

Correct:

  1. Modern technology makes counter-conventional management possible, but the causality also works the other way.
  2. Others felt that technology development was important, but it should not be our key purpose.
  3. Our aim is to contribute to our company’s success and be responsive to our customers.

Comma Rule 2:
Use commas to separate three or more elements in a series.

In a list of three or more elements, place a comma after each element. Place a comma before the and or or that precedes that last element. The Chicago Manual of Style editors use this example to illustrate that the comma is important to give clarity to the sentence: “I accept this award with gratitude to my parents, Mother Teresa and the Pope.”

Comma Rule Examples

Incorrect:

  1. Middle managers are needed for performance reviews compensation adjustments and similar activities.
  2. It is understood, acknowledged and agreed that this is a potential problem between the work units.
  3. Workers who can supervise, direct and report on activities are headed for successful careers.

Correct:

  1. Middle managers are needed for performance reviews, compensation adjustments, and similar activities.
  2. It is understood, acknowledged, and agreed that this is a potential problem between the work units.
  3. Workers who can supervise, direct, and report on activities are headed for successful careers.

Comma Rule 3:
Place a comma between two consecutive adjectives that describe the same noun.

When the text has two or more adjectives that describe the same noun, place commas between them. Test whether the adjectives require commas by placing and between them. If they read well with and between them, then the text should have commas.

Comma Rule Examples

Incorrect:

  1. To many managers, this situation represents an inefficient wasteful use of skills.
  2. Our reporting levels ensure quick accurate responses to customer needs.

Correct:

  1. To many managers, this situation represents an inefficient, wasteful use of skills.
  2. Our reporting levels ensure quick, accurate responses to customer needs.

Comma Rule 4:
Put commas in numbers with four or more digits.

Some suggest that you may omit commas in numbers with only four digits. However, the comma makes the number clearer, so most business writers include it.

Do not place commas in numbers used as codes, such as serial numbers, zip codes, and invoice numbers.

Comma Rule Examples

Incorrect:

  1. Nearly 3000 people attended the conference.
  2. A balance of $1500 is due on Account 12,535.

Correct:

  1. Nearly 3,000 people attended the conference.
  2. A balance of $1,500 is due on Account 12535.

Comma Rule 5:
Use commas to separate parts of dates and addresses.

  • Separate the street, city, and state with commas. Do not place a comma between the state and zip code.
  • Place a comma between the day of the week and date. (Wednesday, August 13)
  • Place a comma before and after the year when the month and day are included in the date. (On August 13, 2015, the two met.)
  • Do not put a comma before and after the year when only the month appears with the year. (They reconciled in August 2015 to make the transition easier.)

Comma Rule Examples

Incorrect:

  1. The work and services will be performed at 333 Shore Drive Bangor Maine.
  2. The work to be performed under this agreement shall be started in March, 2015.
  3. The corporation was formed on or about January 1 2015 and remains in business.

Correct:

  1. The work and services will be performed at 333 Shore Drive, Bangor, Maine.
  2. The work to be performed under this agreement shall be started in March 2015.
  3. The corporation was formed on January 1, 2015, and remains in business.

Comma Rule 6:
Place commas after most introductory words or phrases.

Comma Rule Examples

Incorrect:

  1. Yes the team members will take on new roles based on self-management.
  2. Before we accomplished the transition we operated as senior team members.
  3. Gradually we worked our way out of the management role.

Correct:

  1. Yes, the team members will take on new roles based on self-management.
  2. Before we accomplished the transition, we operated as senior team members.
  3. Gradually, we worked our way out of the management role.

Comma Rule 7:
Use commas to set off elements providing additional information that could be omitted without changing the meaning of the sentence.

Notice that if the information is necessary to define the noun that precedes it or to understand the sentence, you should not use commas to set it off.

Which and That

Use a comma and “which” when the words following the “which” are not necessary to the sentence:

The restaurant, which faced our building, was convenient for our staff. However, if the information is necessary to define the preceding word(s), write “that” with no comma.

The restaurant that faced our building was more convenient for our staff. In the sentence using “that,” the words, “that faced our building,” are necessary to identify which building the writer is describing.

Putting a comma before “who” makes the words following “who” perform the same function as words following a comma and “which”: they aren’t necessary to define the person mentioned in the words before the “who.” However, if the writer has no comma before “who,” the words following “who” perform the same function as words following “that” with no comma: they are necessary to identify the person mentioned just before the “who.”

We’ll invite the division manager, who knows Japanese.
(“Who knows Japanese” is just interesting information about the one division manager to whom the writer is referring.)We’ll invite the division manager who knows Japanese.
(“Who knows Japanese” tells the reader which division manager.)

Comma Rule Examples

Incorrect:

  1. You knew that late or not you were expected to attend the conference.
  2. James Tucker who is the president of Lee Associates has provided excellent leadership to many new retailers.
  3. Employees, who were experiencing personal satisfaction, took more control of their own work.

Correct:

  1. You knew that, late or not, you were expected to attend the conference.
  2. James Tucker, who is the president of Lee Associates, has provided excellent leadership to many new retailers.
  3. Employees who were experiencing personal satisfaction took more control of their own work.

Comma Rule 8:
Use commas to separate transitional expressions when the flow of the sentence is interrupted.

Comma Rule Examples

Transitional expressions: on the other hand, however, in fact, and for example

Incorrect:

  1. Finch on the other hand contends that the work area she had been assigned was only eight feet square.
  2. In some situations for example a supervisor should meet with all those who work under him.
  3. The most effective management style as we shall see later varies from very close to very loose supervision.

Correct:

  1. Finch, on the other hand, contends that the work area she had been assigned was only eight feet square.
  2. In some situations, for example, a supervisor should meet with all those who work under him.
  3. The most effective management style, as we shall see later, varies from very close to very loose supervision.

Comma Rule 9:
Use commas to set off a word or phrase that renames a noun or pronoun that came before it.

These are called appositives.

Comma Rule Examples

Incorrect:

  1. Jan Smith and Joe Thomas married since last August recently became associate partners in the business.
  2. I Edna Summer declare that this is my Last Will and Testament.
  3. Palace Street Diner one of the businesses in question received payment for damages incurred in the fires last month.

Correct:

  1. Jan Smith and Joe Thomas, married since last August, recently became associate partners in the business.
  2. I, Edna Summer, declare that this is my Last Will and Testament.
  3. Palace Street Diner, one of the businesses in question, received payment for damages incurred in the fires last month.

Comma Rule 10:
Use a comma to set off contrasting elements that are not essential to the meaning of a sentence.

Comma Rule Examples

Incorrect:

  1. The employees not the employer made that decision.
  2. Scott rather than Denise will provide feedback.
  3. It was a difficult venture but successful.

Correct:

  1. The employees, not the employer, made that decision.
  2. Scott, rather than Denise, will provide feedback.
  3. It was a difficult venture, but successful.

Comma Rule 11:
Insert commas to help avoid confusion in the reading of the sentence.

Commas can help reduce confusion in a sentence. However, be careful to avoid their overuse. Do not use a comma every place you feel yourself pausing as you read.

Comma Rule Examples

Incorrect:

  1. To Frank Thomas seemed confident in reaching a compromise.
  2. Inside the car damage was evident.
  3. Contrary to his written review the supervisor spoke very highly of Janet.

Correct:

  1. To Frank, Thomas seemed confident in reaching a compromise.
  2. Inside the car, damage was evident.
  3. Contrary to his written review, the supervisor spoke very highly of Janet.
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