A math professor used the phrase "for all practical purposes" during class. A student asked what he meant by that.
"Suppose we line up all the boys on one side of the classroom and all the girls on the other. On a given signal, both groups will walk half the distance towards the middle of the room. On each subsequent signal, each group will walk half the remaining distance. Theoretically, of course, the two groups will never meet. But in reality, after a few signals, the two groups will be close enough for all practical purposes."
