A comma is used in the middle of, and never at the end of a sentence. This is done to make the sentence clearer, especially to separate items in a list. However, overusing commas can complicate a sentence, or render it meaningless. A comma is important to avoid any possibility of misunderstanding a sentence as the following example shows:

While my father was eating, my mother was drinking.
While my father was eating my mother was drinking.
Without the comma, it appears my father was cannibalizing my mother.


A comma is used:

Example: We saw monkeys, porcupines, lions and tigers in the zoo.


Example: Yesterday, as I was jogging in the park, I saw a black baboon.


Example: He told us, "I believe the world is flat."


Example: "Jane, let me show you how to do it."


Example: He is marrying on Tuesday, 1st April.
Example: The explosion happened on 1st January, 2000.


Example: Oh no, it can't be true.
Example: Well, all I can say is it's a waste of money.


Example: Of course, you are always right.
Example: Moreover, the rent is high and the location is not perfect.


Example: 999, Downing Street, Kingston.


Example: Montana, USA.


Example: 2,000 / 20,000


Example: Dear Princess Diana, / Yours sincerely.


Example: The short, puny man was a comedian.


Example: The man, who lives next door, is a circus clown.


Example: Jack is washing the car, and Jill is washing the dishes.