<b>Definition:</b>an association between two Entities where the playing Entity (the part) is a component of the whole (scoper) in the sense of an integral structural component, that is distinct from other parts in the same whole, has a distinct function in the whole, and, as an effect, the full integrity of the whole depends (to some degree) on the presence of this part, even though the part may often be separable from the whole.<b>Discussion:</b>Part is defined in opposition to (a) ingredient (not separable), (b) content (not a functional component), and (c) member (not functionally distinct from other members).