What's a function?

There are tests... for the visual spatial folks the concept of "each x can only have one y" or the "vertical line" test will work. (If you can draw a vertical line through two points, it isn't a function, because the vertical line is the same x, with two different y's.)

For your logical verbal types, though, the idea that "every question -x- can only have one right answer - y. Sometimes two different questions will have the same answer, but you can't have two right answers to the same question... the function might be "how far is it to the next town?" and it might be ten miles for several different situatoins, but it's always *one* answer. It isn't ten miles *and* eight miles."