Disease: A disposition (i) to undergo pathological processes that (ii) exists in an organism because of one or more disorders in that organism. Epilepsy as a disease that disposes to the occurrence of seizures (pathological processes) due to an underlying abnormality in the neuronal circuitry of the brain (physical basis); AIDS as a disease that disposes to non-HIV pathogen persistence and duplication (pathological processes) following opportunistic infections that take advantage of a weakened immune system (physical basis).

Disorder: A causally relatively isolated combination of physical components that is (a) clinically abnormal and (b) maximal, in the sense that it is not a part of some larger such combination. Although each single cell within a tumor is disordered in its own right, for us the disorder is the tumor as a whole; it is the maximal collection of all disordered cells. Other examples of disorders are: mutated genomic DNA, portions of endotoxin in blood, blood with reduced blood cortisol levels causing adrenal crisis. Such disorders are the physical basis of disease. A disease comes into existence because some physical component becomes malformed. In some cases the disorder is a congenital malformation. In other cases it involves a virus or toxin coming in from the outside, or it arises because the absence of a normal bodily component leads to abnormal functioning.