Hospitals are defined by the WHO as organizations that provide both curative and preventive healthcare services, including outpatient care, to the local population. They also serve as centers for training healthcare workers and conducting biomedical research. Hospitals are organized into hierarchical structures with standardized rules, policies, and divisions of labor between clinical specialties and disciplines. The organizational structure typically includes a governing board, administrative departments, and medical/nursing divisions that work together to care for patients, prevent and treat diseases, rehabilitate patients, provide medical education and conduct research. Hospitals can be classified based on size, ownership, clinical specialties, and whether they provide teaching services.