This seem like an odd question and perhaps misplaced on this site but I am interested none the less. I was thinking about the definition of a car. You see, I've brought this up in conversation before and people are usually arrogantly dismissive of it, and say something like “it has 4 wheels and an engine!”; then I inform them that they've just described cars, forklifts, tractors, some planes etc... Then they realize that any true definition would require much more eloquence. But this is where I am stuck, as any definition I can think of does not omit other non-car vehicles or does not include the myriad of car forms. The fact that what is a car is obvious to the observer is testimony to the fact that there is a working definition of it, and if we fail to find one then, to me at least, it suggests that there is some uniquely car trait that we have yet to quantify. I suppose the broader question this raises is are definitions meaningful anyway?