Comma Usage

Comma is a punctuation mark ( , ) used to indicate a separation of ideas or of elements within a sentence. Comma is used in the following ways:

[1] separate items in a series
When we list three or more items, we separate them with commas.

• We have a dog, a cat, and a parrot.
• I bought some oranges, grapes, bananas, and mangoes.

[2] after introductory words or phrases

• Suddenly, the computer shut down.
• In the morning, I get up at 6.
• In my opinion, you should talk to your boss.
• Hearing the news, she was so excited.
• Although it was raining, he came to join our party.

[3] in compound sentences
A comma must precede the coordinating conjunction (FANBOYS).

• We walked, and they drove. 
• He was tired, but he kept running.

A comma must follow the conjunctive adverb.

• He ran out of money; therefore, he had to work harder.
• They like our product; however, they complain about its high cost.

[4] setting off the modifying words or phrases

• Iphone 5, which is a high-end product, is sold to every part of the world.
• Many like Iphone 5, which is a high-end product. 
• Vutha, my new boss, goes to your gym. 

[5] separate parts of the address

• Danielle lives at 5 Foster Lane, Boston, MA 02130.
• The brothers stayed in Dayton, Ohio, before driving on to Nebraska.

[6] separate parts of the date

• My daughter was born on September 15, 1998.
• September 15, 1998, was a big day for our family.