Writing - Comma 3

The more she practises, the better she plays.
We use a comma in the middle of a sentence which contains the more ... , the more ... or the more ... the less… construction.
Common Errors:
The more I know her the less I like her. X comma required!
The more I know her, the less I like her. V comma in the middle of the sentence

World War II began on September 1, 1939, with Germany's invasion of Poland.
We use a comma to separate the day of the month from the year and after the year. If the date is written the according to Europe (Day, Month, Year), then there is no comma.
Common Errors:
I'm preparing for the exam. It's on March 2 2013. X comma required!
I'm preparing for the exam. It's on March 2, 2013. V comma to separate the day of the month from the year
I'm preparing for the exam. It's on 2 March 2013. V European style

He finally came in, in tears.
We use commas to separate words repeated within a sentence to avoid confusion.
Common Errors:
I really really like my dog. X comma required!
I really, really like my dog. V comma between the repeated words

It is the tablet I'm looking for, not the laptop.
A comma is used to separate contrasting parts of a sentence.
Common Errors:
This is my MP3 player not yours. X comma required!
This is my MP3 player, not yours. V comma before NOT

Her objection, therefore, was ignored.
The comma is used to surround words such as therefore and however when they are used as interrupters.
Common Errors:
Partnership however is a complicated dance. X comma required!
Partnership, however, is a complicated dance. V HOWEVER surrounded by two commas

Neither Carol nor Richard has got a car.
Don't use a comma to separate the two halves of a correlative conjunction.
Other correlative conjunctions: both ... and | either ... or | whether ... or | not only ... but also.
Common Errors:
We could either watch TV, or go to the cinema. X no comma!
We could either watch TV or go to the cinema. V no comma before OR

A student from California won a $100,000 scholarship.
In numbers longer than four digits, commas separate the numbers into groups of three, starting from the right side.
Common Errors:
One of my best friends lost $50000 at the casino last night. X comma required!
One of my best friends lost $50,000 at the casino last night. V comma after 50

George and his friends played cards and watched films all night long.
Do not use a comma in front of every and in the sentence.
Common Errors:
She took guitar lessons for ten years, and today is an accomplished performer. X no comma!
She took guitar lessons for ten years and today is an accomplished performer. V no comma before AND