 What is included in D? We can give an open-ended list of candidate relations: grounding, dependence between wholes and their parts (known as mereological or compositional dependence), realization, existential dependence, essential dependence, and, controversially, even causal dependence (on the link to causation, see Bernstein 2016; Koslicki 2016; Schaffer 2016b; Shaheen 2017). The list is open-ended partly because there is disagreement about what counts as a metaphysical dependence relation in the relevant sense and partly because there may be metaphysical dependence relations that we wish to rule out. A possible criterion (i.e., the “relevant sense”) to be included in the list is that the dependence relations in question must have at least some features in common, such as, perhaps, transitivity. Furthermore, two philosophers may disagree, say, about whether compositional dependence is a genuine metaphysical dependence relation. So, for these two philosophers,  (AI)  will produce a different definition of fundamentality, because the scope of D is different. We will not attempt to give a complete list or to define all these different kinds of metaphysical dependence, but for further details on some of them, see the separate entries on  ontological dependence  and  metaphysical grounding.[5] 