"The term disease comes from the Latin infirmitas, which literally means "lack of firmness." The definition of disease according to the World Health Organization (WHO) is "Alteration and deviation from the physiological state in one or more parts of the body." , due to generally known causes, manifested by characteristic symptoms and signs, and whose evolution is more or less predictable.

Health and illness are an integral part of life, the biological process and environmental and social interactions. Generally, disease is understood as the loss of health, the negative effect of which is a consequence of a structural or functional alteration of an organ at any level."