A comma ( , ) is used to show a pause or a separation. There are two places in a friendly letter when you will use a comma: in the greeting and in the closing.
The greeting in a letter is where you address the person to whom you are writing. If you are writing to Mom, you say Dear Mom. In the letter, those two words will be on a line by themselves, and you will put a comma after the two-word greeting.
Here is an example of the beginning of a friendly letter:
Dear Mom,
We arrived at the campground just before dinner.
Notice how the greeting sits on its own line and is followed by a comma. The comma separates the greeting from the body of the letter.
When you have finished writing the body of your letter, you write a closing word, a comma, and then your name.
A closing in a friendly letter looks like this:
Love, Susan
or
Yours truly, Sam
or
Sincerely, Mrs. Johnson
There are two important places for a comma in a friendly letter: After the greeting, just before you begin the body of the letter; and after your closing word, just before you sign your name.