Today I went to a friend house and sleep over. It was fun.

 

-a/ an use to show individual thing.

-a/ an use when using of that word is first time.

-an use when that word is vowel.

-a use when show something little. ( a few, a liitle, a bit of...)

-the use when the person I speak have same understanding of that word. 

-the use when that thing exsisting only one. (the moon, the earth, the president, the left/right...)