Commas in English

English Comma Usage

Commas are used

I) seperate independent clauses
The following conjunctions (so-called coordinating conjunctions) are used in such case:
and, but, for, nor, or, so & yet¹

The students asked for a second chance to rewrite the exam, but the teacher did not grant it.
II) after introductory

a) subclauses

b) phrases

c) words
a) If you leave the door open, the dog might run away.

b) As a matter of fact, I’m going on vacation to Hawaii next week.

c) Unfortunately, he was convicted of a crime and put into jail.
III) when

a) subclauses

b) phrases

c) words

appear in the middle of the sentence.
a) Jill, who was sitting behind her desk, gave Tim a smile.

b) We, as a matter of course, will contact your former employer.

c) We have, however, found several severe errors.

 IV) to set off three or more words,
phrases or mainclauses in a serious.

She went into the living room,  
sat down, and played chess on the computer.

V) to set off two or more coordinate adjectives, that is, the meaning
does not change when the order
is altered.
We had to travel over several narrow,  
winding, treacherous roads.

VI) at the end of a sentence
in order to indicate a pause.
He was merely ignorant, not stupid.

VII) to set off a nonrestrictive
(also non-defining) relative clause².
Theodore Roosevelt, who was leader 
of the famous rough riders, became
president in 1901.

VIII) when someone is addressed
Susan, can you help me do the
dishes please?

IX) when a direct quotation
is included.
Descartes said,“I think, therefore I am.“

X) to show an appositive³.
Bill Clinton, former US president,
is still very popular in Europe.

XI) in dates.
Yes, July 17, 1972, was the date
of his birth.

XII) seperate identical words.
How it is, is how it’s always been.

XIII) in front of tag questions.
Bring me the tools, will you?
XIV) after digits indicating

XV) after a

a) salutation

b) farewell
in letters.
a) Dear John,

b) Sincerely yours,

¹ Note that ‘but’ and ‘and’ do not take a comma when both are relatively short.

² restrictive relative clause= they tell us which person or thing, or which kind of person or thing, is meant;

non-restrictive relative clause = they tell us more about a person or thing that is already identified.

³ When an appositive is only one word, no comma is needed.
Thanks to Kai.