Generally, diseases are physiological abnormalities, determined on the basis of a change in form, function or feeling, or on the basis of a physiological measure falling outside of some pre-determined range of values (normal range).

Three main classes or dimensions of cause are popularly grouped under the following headings:

Genetic: all and any heritable factors associated with a disease Environment: all and any non-heritable factors, particularly those related to physical and/or internal physiological environment.

Lifestyle: the exposure history of a person or activities, habits, and locations that constitute their sequence of lived environments and acts. This is dependent upon a person�s location, acts, and interactions.

These three groups constitute the majority of popular �explanations� for why disease occurs where and when it does. This disease is due to �faulty genes�, that disease is due to �environmental influences�, another disease is due to �lifestyle factors�, and so on. However, �explanations are not causes, but everywhere they are treated as if they were�. (quote, source unknown).

However, there are some clearer and more specific criteria for determining if a agent is causally connected to an effect we label a disease.