My point was that categorizing limbs (differentiating them from one another) is done by function. Now that I think about it limb isn't what I had in mind anyway

My point was that categorizing limbs (differentiating them from one another) is done by function. Now that I think about it limb isn't what I had in mind anyway, what I meant to say was that we categorize parts of the body in terms of function. But you're right, limbs are not defined by function.