 The notion of “ground” stormed into contemporary analytic metaphysics in the beginning of the twenty-first century, but the roots of the notion go back to Aristotle (for an overview, see Fine 2012). Sometimes grounding is understood as “metaphysical explanation”. To be more precise, when some x is grounded in some y, it is usually thought that y explains x, and grounding either is that explanatory relationship or ‘backs’ that explanation (there is a lot of debate on these issues, see the separate entry on  metaphysical grounding).  Moreover, the status of y is generally thought to be somehow prior to that of x—grounding is typically understood to express priority between things. For instance, we might say that the members of a set are prior to the set itself; the existence of the set is grounded in its members. Or to take a more concrete example, the existence of any given composite object is grounded in the existence of its parts. For instance, we might suggest that the existence of any given water molecule is grounded in the existence of hydrogen and oxygen atoms. Somewhat more controversially, we might also say that mental states are grounded in physical states. In each of the mentioned examples there appears to be an ontological dependence relation between the grounded entity and the grounding entity or entities. In fact, we have already discussed some of these examples in terms of ontological dependence above. This naturally leads one to question whether grounding just is (a variety of) ontological dependence—or whether ontological dependence is grounding. One motivation for finding a systematic link between ontological dependence and grounding is that it would be more parsimonious than having two primitive notions (for discussion, see Correia &amp; Schnieder 2012b).