What does it mean for something to exist?

(First paragraph.) Ontology is often described as the inquiry into what exists, but there is some disagreement among (meta-) ontologists about what “existence” means and whether there are different kinds or senses of “existence” or just one; that is, whether “existence” is equivocal or univocal. Furthermore, there is a growing number of philosophers (many of whom take inspiration from Aristotle’s metaphysical writings) who argue that ontology should not be concerned so much with what exists, but with what is fundamental or real (or something similar). Each of the positions in this debate is centered on a concept or small class of concepts that is intended to capture what ontology is about. Examples of such ontological core concepts are: existence, subsistence, Dasein, being, independent being, being real, being fundamental, being a fundamental constituent of reality, being irreducible. This paper intends to answer the twofold question of what (kind of notions) these ontological core concepts are, and how (and how much) they (can) differ. I will argue that there can be no difference between such concepts other than differing domains, and that any domain is a restriction in a maximally expanded universe, and therefore, equivalent to a (restricting) property. Furthermore, such differences between domains (or restricting properties) are intertranslatable, and consequently, there is not much room for substantial difference. Whatever difference remains is largely due to differences in focus or differences in the (phrasing of) questions ontologists try to answer.