Tricky question

A young boy of 5 was staying with his grandmother for a few days. He had been playing outside her house for a while when he came into the house. "Grandma, what is it called when people are sleeping on top of each other?"

She was a little taken aback, but decided to tell him the truth. "It is called sexual intercourse darling."

The little guy just said "OK" and went out to play again.

In a few minutes he came back inside again and said angrily to his grandmother: "Grandma, it's not called sexual intercourse! It's called bunks; and Timmy's mother wants a word with you!"