Wow, that's the best explanation I've read. Very intuitive. Not to say I didn't know the original definition at some point but having such a concept tied to a

Wow, that's the best explanation I've read. Very intuitive. Not to say I didn't know the original definition at some point but having such a concept tied to a concrete example makes it much easier to remember. It makes me wish that most mathematical concepts were explained with some kind of real world analogy.