Functional States

The word "functional" has two meanings. The first is that it works the way it is supposed to (i.e. being not broken). The second is that something operates in the se way is a completely different thing. 

If you go out to the farm and see a big red tractor that turns on and can pull a trailer around the field, then it is a functional tractor (in the first definition). If you go to a farm and you see a station wagon pulling a hitched-up trailer around the field, then it's a function tractor (in that it isn't actually a tractor, but it functions in all the same ways that a tractor does). 

This second definition I find endlessly fascinating. It's like saying "if it walks like a duck and talks like a duck, then it is functionally a duck." It doesn't matter if it's a duck or a man in a duck suit or a fox in a zebra suit; when it covers all the factors that are relevant to determining duckness, then it doesn't matter what things make it not a duck; for all intents and putposes, it's a duck.