 ‘Non-determinable necessities’ are those features of a determinable not allowing for variation (e.g., being three-sided, in the case of triangularity); condition (2) registers that sharing of non-determinable necessities is also required for determination, in addition to the increase in specificity associated with conditions (1) and (3), registering that determinates differ with respect to the values of one or more determination dimensions associated with the determinable.