A disease is any condition which results in the disorder of a structure or function in a living organism that is not due to any external injury. The study of disease is called pathology, which includes the study of cause. Disease is often construed as a medical condition associated with specific symptoms and signs. It may be caused by external factors such as pathogens or by internal dysfunctions, particularly of the immune system, such as an immunodeficiency, or by a hypersensitivity, including allergies and autoimmunity.
Before the curing of a strong disease, Even in the instant of repair and health, The fit is strongest; evils that take leave, On their departure most of all show evil.
William Shakespeare, King John (1598), Act III, scene 4, line 112.
Using light to produce either electricity or hydrogen, dye-sensitised solar cells (DSSCs) are currently the most efficient third-generation solar technology. Increases in their conversion efficiency through better understanding of how light-absorption materials function will make them attractive for large-scale deployment.