The term for the study of diseases is "pathology." Pathology is a branch of medicine that examines the causes, effects, and nature of diseases. It involves the study of various disease processes, including their development (etiology), biochemical mechanisms, and their impact on tissues and organs. Pathologists use a variety of techniques, including lab testing and microscopy, to diagnose diseases, determine their progression, and guide treatment decisions. Different subspecialties within pathology focus on specific fields, such as molecular pathology, forensic pathology, and clinical pathology. This discipline is crucial for improving patient care and advancing medical research.