Use commas in lists, clauses and to mark off words such as "therefore". Commas help you to clarify what you mean when you write. Use commas to provide slight pauses and help your reader to understand you!
Commas operate as visual markers which separate parts of the sentence so that you can understand it better. When reading aloud, we know to pause slightly where a comma appears and to pause a little longer where a semicolon or full stop is used. Similarly, when writing, we use punctuation to shape the writing and distinguish between phrases, clauses and items in lists.The quiz on Revising Punctuation (Commas to Separate Clauses) gives you some practice with one use of the comma. Here you can practise punctuating lists. Each item in a list should be followed by a comma. The only exception is the next-to-last item, which should be followed by the word "and", but does not need a comma: "I have learned how to use commas, exclamation marks, question marks, colons, semicolons and speech marks!"
Be careful with words such as "therefore" and "however". These should not be used with bracketing commas, which usually creates a sentence with a comma splice, as here: "The speaker was ordered to stop talking, however, she continued." COMMA SPLICE ALERT! This should instead be: "The speaker was ordered to stop talking; however, she continued."
Test your punctuation skills with this quiz.