We were at a friend's cabin a few weeks back and Amanda had left her colouring stuff outside on the grass the previous night. The next morning, we asked her to go out and get it and told her that it might be a little wet. She asked the usual "why?". We tried to explain that it was because of the dew. She asked "what is dew?". We explained that in the fall when it gets colder at night that water sometimes forms on things because of the temperature.
Our 4 year old replied. "Oh, you mean condensation"