The comma
Règles EN
Definition
The comma marks a brief pause within a sentence. It separates items in lists, clauses, and phrases to aid readability.
1
Spacing
The comma follows the preceding word with no space before it. A single space follows.
Avant 
Pas d'espace
Pas d'espace , The comma
Après
bread
,butter,and milk
bread,butter,and milk
2
The Oxford comma
In English, a comma before the final conjunction in a list (the Oxford or serial comma) is widely recommended to prevent ambiguity. It is standard in US English and in many UK style guides.
I bought eggs,cheese and milk.
I bought eggs,cheese,and milk.
Oxford comma prevents ambiguity
3
Comma and quotation marks
In US English, the comma goes inside the closing quotation mark. In UK English, it goes outside.
"I will be there," she said. (US)
US English
'I will be there', she said. (UK)
UK English