substance (from Latin, substantia; from substare, be inder, be present, b firm, support) 1. that which is the underlying ground (support, substratum] of all phenomena. 2. that upon which everything else depends for its existence and (usually) which itself does not depend for its existence on anthing else. 3. that which is real; real existence as opposed to appearance or illusion; that which exists in and of itself: 4. that without which a thing would not exist, would not be what it is. 5. that in which properties inhere; that which possesses properties but which itself is not a property 6. that which endures throughout the changes of its properties. 7. the real ESSENCE of a thing; that without which a thing could not be what it is and would be something else. 8. the primary and the most important aspect of a thing; the essential nature of a thing in terms of which a thing is recognized and defined and without which it could not exist as that thing. 9. MATTER; the material of a thing. 10. BODY; the body of a thing.