The punctuation mark comma (,) has the following uses.

To connect the items in a list

Commas are used to connect the items in a list, except for the last two which are usually connected by a coordinating conjunction like and or or.

• My favorite writers are Charles Dickens, Emily Bronte and Jane Austen.
• The Three Musketeers were Arthos, Porthos and Aramis.

To join two complete sentences into a single sentence

A comma is used to join two complete sentences into a single sentence. It is usually followed by a connecting word like and, but, or, while or yet.

• She had very little to live on, but she would never take what was not hers.

Notes

Short clauses connected by and, but or or are not usually separated by commas.

• She is poor but she is honest. (NOT She is poor, but she is honest.)

To show that certain words have been omitted

A comma can be used to show that certain words have been omitted.

• Alice decided to order to steak pie and Peter, the chicken pathia. (The omitted words are ‘decided to order’.)

Subordinate clauses

When subordinate clauses begin sentences, they are often separated by commas.

• When the rain stopped, we went out. OR We went out when the rain stopped.

Commas are also used to set off words or expressions that interrupt the natural progression of a sentence

• My friends, however, did not come.
• John had, surprisingly, did everything.

To separate adjectives used in the predicative position

Adjectives used in the predicative position are always separated by commas.

• He is tall, dark and handsome.
• That was a lovely, long, cool drink.

Sometimes commas are not used between the last two adjectives which are usually separated by a conjunction like and or or.

Commas are sometimes dropped between short adjectives.

In direct speech

A comma is generally used between a reporting verb and a piece of direct speech.

• Looking at the painting, she said, ‘I like this one.’

If the reporting verb follows a piece of direct speech, we usually use a comma instead of a full stop before the closing quotation mark.

• ‘I don’t like this,‘ said Jane.

Numbers

Large numbers are often divided into groups of three figures by using commas.

Examples are:

• 5,768 (NOT 5.768)
• 6, 567, 873

Commas are sometimes not used in four figure numbers.

• 5,378 or 5378

Commas are never used in dates.

• The Year 1953 (NOT The Year 1,953)

Cases where commas are not used

Commas are not used before that, what, where etc in indirect speech structures.

• Nobody realized that the child was missing. (NOT Nobody realized, that the child …)
• She didn’t know what to do. (NOT She didn’t know, what to do.)

Commas are not used between two grammatically independent sentences. Instead we use a full stop or a semicolon.

• The blue dress was cheap. On the other hand, the pink dress was better. OR The blue dress was cheap; on the other hand, the pink dress was better. (NOT The blue dress was cheap, on the other hand, …)