When speaking, we can pause or change the tone of our voices to indicate emphasis. When writing, we use punctuation to indicate these places of emphases. Comma tells the reader to pause, just as the blinking yellow light tells a driver to slow down and proceed with caution. [1] Commas in the wrong places can break a sentence into illogical segments or confuse readers with unnecessary and unexpected pauses. [2] The rules of using comma are therefore important to know when we read and write.


  • Definition & Misunderstandings
  • When to Use
  • Comma Abuse
  • References
  • See Also

Definition & Misunderstandings

The comma ( , ) is a punctuation mark “used to separate the items in a list or to show where there is a slight pause in a sentence” according to the Oxford Advanced Learner’s English-Chinese Dictionary.

Using commas correctly may seem mysterious, it can be easy if you follow a few overall principles and beware of popular myths of comma usage:
  • Long sentences need a comma. A really long sentence may be perfectly correct without commas. The length of a sentence does not determine whether you need a comma.
  • You should add a comma wherever you pause. Where you pause or breathe in a sentence does not reliably indicate where a comma belongs. Different readers pause or breathe in different places.
  • Commas are so mysterious that it's impossible to figure out where they belong! Some rules are flexible, but most of the time, commas belong in very predictable places. [3]

When to Use

1.Listing elements in a series
Comma can be used to separate three or more items (words, phrases or clauses) listed in a sentence, for example:
  • The gardener sprayed the grass, tress and shrubs with pesticide.
  • George Washington was first in war, first in peace and first in the hearts of his countrymen.

When giving a short and simple list of things in a sentence, the last comma (right before the conjunction–usually and or or) is optional, but it is never wrong. If the items in the list are longer and more complicated, you should always place a final comma before the conjunction. [3]
  • EITHER: You can buy life, liberty, and the pursuit of happiness in Los Angeles.
  • OR: You can buy life, liberty and the pursuit of happiness in Los Angeles.
  • BUT ALWAYS: A good student listens to his teachers without yawning, reads once in a while, and writes papers before they are due.

2.Before the FANBOYS in a compound sentence

Use a comma before and, but, or, nor, for, so, or yet (taken together, the first letters spell “FANBOYS.”) to join two independent clauses that form a compound sentence. See examples:

A compound sentence must have two independent clauses. If you do not have two subjects and two verbs separated by the FANBOYS, you do not need to insert the comma before the FANBOYS. In other words, if the second grouping of words isn’t a complete thought, don’t use a comma. [3] Look at this example:

n the above example, two verb groups are being joined by and. The second verb group does NOT have a subject; thus it is NOT an independent clause. Therefore, NO comma belongs before and. However, we can make this sentence into a compound sentence by simply making the last verb part into an independent clause. [4]


3.After an introductory word, phrase or clause

Most of the sentences we compose really consist of a short core sentence with many details added to that core sentence. Frequently, we add information to sentences by attaching one or more words to the front or back of the core sentence. [1]
  • Moreover, some will knit booties for you if you ask nicely.
  • In fact, Godzilla is just a misunderstood teen lizard of giant proportions.
  • If you discover that you feel nauseated,then you know you’ve tried my Clam Surprise.

4.With nonessential elements

We often insert a group of words into the middle of a sentence. In order to tell a reader that a group of words is a nonessential part, we place commas in front and in back of the group of words, for example:
  • Mr. Jones, the foreman at the plant, is on vacation.

However, if omitting the group of words would drastically change the meaning of the sentence, then those words are not a component; rather, they are essential to the meaning of the sentence. [1] For example, the two sentences below have different meanings:
  • Banks which hold over a billion dollars in assets are rare.
  • Banks, which hold over a billion dollars in assets, are rare.


If you have two or more adjectives that are not joined by a conjunction (usually and) and both/all adjectives modify the same word, put a comma between them.
  • On a stark, cold, gray day the men began their search for the missing child.

6.More detailed usages

Here are the main usages of comma. If you want to know more detailed categories of comma’s usages, refer to .

Comma Abuse

The governor-elect promised to work to change the policy.
The governor-elect, promised to work to change the policy.
No comma between subject and object.
The U.S. has a government of the people.
The U.S. has a government of, the people.
No comma between object and object compliment
I have tried to understand Marshall, but his behavior continues to puzzle me.
I have tried to understand Marshall but, his behavior continues to puzzle me.
No comma used after the conjunction linking the core sentence.
The cat scratched at the door while I was eating.
The cat scratched at the door, while I was eating.
No comma after the main clause when a dependent clause follows it.
Kurt loves some unusual ideas, such as reincarnation, transmigration, and metal telepathy.
Kurt loves some unusual ideas, such as, reincarnation, transmigration, and metal telepathy.
No comma after such as or like.

(Cited [2] & [5])


[5] Li Mei and Diao Huiyao, An Intermediate Course in Writing, High Education Press.

See also
Introduce comma usage with plenty of examples. Also quiz at the bottom of the page.
Online exercises not only about comma usage but also other grammar and vocabulary items.
Overall glance with contents such as the history of comma and differences between American and British usage.