How do you exactly define a grip?

[New Daddy]

I understand that grips are really, really important because the ideal hitting zone is determined by your grip.
But different instructional materials define grips differently.

One school defines grip by the location of the "V" of your hand - the "V" that is formed between your thumb and index finger.
According to this school, if the V rests on the top bevel, it's the continental grip.

Another school defines grip by the location of the heel pad and index knuckle. According to this school, if the heel pad of your palm and index knuckle rest on the 1 o'clock bevel, it is the continental grip.

I've tried both definitions and they do not exactly match. For example, if I rest the V of my hand on the top bevel (i.e., continental grip by the first definition), the heel pad of my palm and index knuckle rest on the 3 o'clock bevel (i.e., easter grip by the second definition).

Which definition is more accurate?

 

[volusiano]

If you think about it, the V and the heel pad cover a pretty wide area when you grip on the handle, and therefore is too ambiguous, in my opinion. Their locations also become dependent on the hand size relative to the grip size.

On the other hand, the inside knuckle of your index finger is more localized to a smaller spot, and not dependent on the hand size or grip size. So it's better to use the knuckle as a reference point compared to the other 2 places.

If your knuckle is at the 1 o'clock bevel (or more precisely the bevel between the noon and 3 o'clock bevels), that would be the continental grip. At this point, your V or palm heel can be at different spots depending on the hand size and grip size.

 

[nyc]

This should clarify things:
http://www.fuzzyyellowballs.com/videos/index.php/view/945/125/Introduction_to_the_Tennis_Grips