The study of the nature of diseases with regard to structural and functional changes: Pathology is the branch of medical science that deals with the origin, nature, and course of diseases.

Pathology was originally the study of “suffering”.

1. A medical specialty that is concerned with the diagnosis of diseases that are based on the normally visible, microscopic, and molecular examination of organs, tissues, and whole bodies: An anatomic pathology is an autopsy that is done after a person's death.
2. The anatomical investigation of changes in the function, structure, or appearance of organs, or tissues, including postmortem examinations and the study of biopsy specimens: Judy was especially interested in the nature of diseases and their causes, so she decided to specialize in anatomic pathology in medical school.

A branch of medicine concerned with determining the cause of deaths usually for civil or criminal law cases: Floyd thought that forensic pathology sounded very exciting and decided to specialize in this field of work.

The forensic pathologist performs autopsies to determine the cause of a death, such as examining a bullet wound to the head, exsanguination, strangulation, etc. and the manner of a death (including homicide, accident, natural, or suicide).

Forensic pathologists also work closely with the coroner (England and Wales) or medical examiner (United States). The examination of dead bodies (autopsy or post mortem) is a subset of anatomical pathology.

Forensic pathologists are often also known as forensic medical examiners or police surgeons.

A particular area in botanical science that is concerned with the diseases of verdure: Plant pathology involves research about microbes and the environmental factors that can cause diseases in plants, the factors and processes involved in the development of diseases, and the methods of preventing and controlling plant diseases.