 On the Sarvāstivādin definition, for an entity to be real, it does not need to be ultimately real, exclusively. For a thing to be ultimately real is for that thing to be “foundationally existent” (dravya-sat / rdzas  yod)[3]  in contrast with being “compositely existent” (avayavidravya / rdzas grub). By “foundationally existent” the Sarvāstivādin refer to the entity which is fundamentally real, the concept or the cognition of which is not dependent on conceptual construction, hence not conceptually existent (prajñaptisat) nor a composition of the aggregative phenomena. In the case of foundational existent there always remains something irreducible to which the concept of the thing applies, hence it is ultimately real. A simple entity is not reducible to conceptual forms, or conventional designations, nor is it compositely existent entity. We will have lot more to say on this point shortly.