While visiting my parents, Emily loved to play on Mom and Dad's "playground". One time while we were out on the swings, Emily fell dramatically off the back of her swing.
"I did that on purpose." she said.
"Oh yeah?" I asked. "What does it mean when you do something 'on purpose'?"
"It means when you really want to do something."
"Really?" I asked, "and what does it mean when you do something on accident?"
"It means you don't get in trouble."