Pathology is the study of the causes and effects of disease or injury. The word pathology refers to the study of disease in general, incorporating a wide range of bioscience research fields and medical practices. However, when used in the context of modern medical treatment, the term is used in a more narrow fashion to refer to processes and tests which fall within the contemporary medical field of "general pathology," an area which includes a number of distinct but inter-related medical specialties that diagnose disease through analysis of tissue and body fluid samples. Idiomatically, "a pathology" may refer to the predicted or actual progression of particular diseases, the affix path is sometimes used to indicate a state of disease in cases of both physical ailment and psychological conditions. A physician practicing pathology is called a pathologist; as a field of general inquiry and research, pathology addresses four components of disease: cause, mechanisms of development, structural alterations of cells, the consequences of changes.
In common medical practice, general pathology is concerned with analyzing known clinical abnormalities that are markers or precursors for both infectious and non-infectious disease and is conducted by experts in one of two major specialties, anatomical pathology and clinical pathology. Further divisions in specialty exist on the basis of the involved sample types and physiological systems, as well as on the basis of the focus of the examination. Pathology is a significant field in medical research; the study of pathology, including the detailed examination of the body, including dissection and inquiry into specific maladies, dates back to antiquity. Rudimentary understanding of many conditions was present in most early societies and is attested to in the records of the earliest historical societies, including those of the Middle East and China. By the Hellenic period of ancient Greece, a concerted causal study of disease was underway, with many notable early physicians having developed methods of diagnosis and prognosis for a number of diseases.
The medical practices of the Romans and those of the Byzantines continued from these Greek roots, but, as with many areas of scientific inquiry, growth in understanding of medicine stagnated some after the Classical Era, but continued to develop throughout numerous cultures. Notably, many advances were made in the medieval era of Islam, during which numerous texts of complex pathologies were developed based on the Greek tradition. So, growth in complex understanding of disease languished until knowledge and experimentation again began to proliferate in the Renaissance and Baroque eras, following the resurgence of the empirical method at new centers of scholarship. By the 17th century, the study of microscopy was underway and examination of tissues had led British Royal Society member Robert Hooke to coin the word "cell", setting the stage for germ theory. Modern pathology began to develop as a distinct field of inquiry during the 19th Century through natural philosophers and physicians that studied disease and the informal study of what they termed “pathological anatomy” or “morbid anatomy”.
However, pathology as a formal area of specialty was not developed until the late 19th and early 20th centuries, with the advent of detailed study of microbiology. In the 19th century, physicians had begun to understand that disease-causing pathogens, or "germs" existed and were capable of reproduction and multiplication, replacing earlier beliefs in humors or spiritual agents, that had dominated for much of the previous 1,500 years in European medicine. With the new understanding of causative agents, physicians began to compare the characteristics of one germ’s symptoms as they developed within an affected individual to another germ’s characteristics and symptoms; this realization led to the foundational understanding that diseases are able to replicate themselves, that they can have many profound and varied effects on the human host. To determine causes of diseases, medical experts used the most common and accepted assumptions or symptoms of their times, a general principal of approach that persists into modern medicine.
Modern medicine was advanced by further developments of the microscope to analyze tissues, to which Rudolf Virchow gave a significant contribution, leading to a slew of research developments. By the late 1920s to early 1930s pathology was deemed a medical specialty. Combined with developments in the understanding of general physiology, by the beginning of the 20th century, the study of pathology had begun to split into a number of rarefied fields and resulting in the development of large number of modern specialties within pathology and related disciplines of diagnostic medicine; the term pathology comes from the Ancient Greek roots of pathos, meaning "experience" or "suffering" and -logia, "study of". The modern practice of pathology is divided into a number of subdisciplines within the discrete but interconnected aims of biological research and medical practice. Biomedical research into disease incorporates the