Pathology is a significant component of the causal study of disease and a major field in modern medicine and diagnosis. The term pathology itself may be used broadly to refer to the study of disease in general, incorporating a wide range of bioscience research fields and medical practices or more narrowly to describe work within the contemporary medical field of "general pathology," which includes a number of distinct but inter-related medical specialties that diagnose disease—mostly through analysis of tissue, cell, and body fluid samples. Used as a count noun, "a pathology" can also refer to the predicted or actual progression of particular diseases and the affix path is sometimes used to indicate a state of disease in cases of both physical ailment and psychological conditions . Similarly, a pathological condition is one caused by disease, rather than occurring physiologically.

As a field of general inquiry and research, pathology addresses four components of disease: cause/petiology, mechanisms of development , structural alterations of cells , and the consequences of changes . In common medical practice, general pathology is mostly 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 (comparing, for example, cytopathology, hematopathology, and histopathology), organs and physiological systems , as well as on the basis of the focus of the examination .The sense of the word pathology as a synonym of disease or pathosis is very common in health care.