Quackery refers to the promotion or practice of medicine or treatment that lacks scientific validity or empirical evidence. Historically and presently, it encompasses any system of medical belief or cure claim that is based on pseudoscience, folklore, or unsubstantiated conjecture rather than through rigorous scientific methodology and established biological or physical principles. These practices often appear to provide relief or cure but generally fail to pass the standards of modern diagnostic and therapeutic verification. The academic study of quackery examines the historical relationship between commercial interests, popular belief, and legitimate scientific medical advances, helping to delineate the boundary between evidence-based healthcare and unproven remedies.