Medicine is the science and practice concerned with maintaining health, preventing and identifying disease, treating illness and injury, and relieving suffering. It encompasses scientific research, clinical care, rehabilitation, and care near the end of life. Modern medicine combines knowledge of the human body with evidence about interventions, professional judgment, and patients’ circumstances and preferences. Although the term sometimes refers specifically to physicians’ work or to nonsurgical specialties, medical care depends on collaboration among many professions.
Historical development
Organized healing practices developed in many societies. Written records from ancient Egypt and Mesopotamia describe injuries, symptoms, remedies, and procedures, often alongside religious explanations. In ancient Greece, texts associated with the Hippocratic tradition emphasized observation and natural explanations of illness, although their physiological theories differed substantially from modern knowledge. Medical traditions also developed in South Asia and East Asia, including the practices and texts now associated with traditional Chinese medicine.
Scholars working in the medieval Islamic world translated, evaluated, and extended earlier medical knowledge. Hospitals and medical teaching developed in different forms across regions. During the Renaissance, anatomical investigation and printed texts expanded the study and circulation of knowledge about the body. Andreas Vesalius’s anatomical work and William Harvey’s account of blood circulation were important developments in European medicine.
In the nineteenth century, anesthesia, antiseptic practices, laboratory investigation, and the germ theory of disease transformed explanations of infection and aspects of clinical care. Twentieth-century developments included antibiotics such as penicillin, improved imaging, and increasingly specialized hospital services. These changes occurred alongside advances in sanitation, nutrition, and disease prevention; changes in population health cannot be attributed to clinical treatment alone.
Scientific foundations and specialties
Medicine draws extensively on biology and related experimental sciences. Anatomy studies bodily structure, while physiology investigates how organs and systems function. Pathology examines the changes associated with disease, including abnormalities in tissues and cells. Pharmacology studies how drugs interact with living systems, including their actions, disposition, and adverse effects.
Genetics helps explain inherited conditions and variation in disease susceptibility. Microbiology investigates organisms involved in infection, while research on the immune system informs understanding of infection, allergy, and immune-mediated disease. These fields overlap: a single condition may involve molecular changes, organ dysfunction, environmental exposures, and social circumstances.
Clinical specialties may be organized around age groups, organ systems, diseases, or methods of care. Internal medicine concerns many adult illnesses; pediatrics focuses on children; obstetrics and gynecology address pregnancy and reproductive health; psychiatry concerns mental disorders. Surgery uses operative techniques to investigate or treat conditions. Family medicine, emergency medicine, radiology, and laboratory specialties have distinct but interconnected roles. Specialty boundaries and training structures vary between countries.
Clinical assessment and care
Clinical assessment commonly begins with a medical history and physical examination. The history includes symptoms, previous illnesses, medication use, and relevant family and social information. Examination findings help guide further investigation. Laboratory tests and imaging can provide additional evidence, but their interpretation depends on the clinical setting.
A diagnosis identifies a condition or provides an explanation for a patient’s findings. Clinicians often construct a differential diagnosis: a set of plausible explanations assessed using further information. Diagnostic conclusions may remain provisional because symptoms overlap between conditions, tests are imperfect, and illnesses change over time. Prognosis concerns the expected course and possible outcomes of a condition.
Treatment may involve medicines, procedures, psychological therapies, supportive care, or combinations of approaches. Some interventions address an underlying cause; others control symptoms or reduce complications. Rehabilitation supports functioning after illness or injury. Palliative care addresses symptoms and other burdens of serious illness and can accompany disease-directed treatment. Clinical outcomes include survival, function, symptom burden, and quality of life.
Evidence and uncertainty
Evidence-based medicine integrates relevant research evidence with clinical expertise and patients’ values and circumstances. It is a framework for evaluating decisions, rather than a claim that every medical question has a definitive answer.
A randomized controlled trial compares interventions using random allocation, which helps reduce systematic differences between comparison groups. Observational studies, diagnostic studies, laboratory research, and qualitative investigations answer other kinds of questions. Epidemiology studies the distribution and determinants of health-related events, while statistics provides methods for analyzing evidence and expressing uncertainty.
Research findings are assessed for bias, precision, relevance, and reproducibility. Systematic reviews bring together studies addressing a defined question. Clinical guidelines translate evidence into recommendations, but their applicability depends on the population and setting. Benefits and harms may differ between individuals, and some adverse effects become apparent only after an intervention is widely used.
Health services and prevention
Medical practice operates within a health system that includes personnel, facilities, financing, information, and regulation. Primary care provides accessible, continuing services and coordinates referrals. More specialized services may be delivered in hospitals or outpatient centers. Care is often shared among physicians, nurses, pharmacists, therapists, and other professionals.
Public health focuses on populations rather than primarily on individual encounters. Its activities include surveillance, sanitation, occupational health, and vaccination programs using vaccines. Prevention and treatment are also shaped by social determinants of health, including housing, working conditions, and access to services.
Ethics and professional standards
Medical ethics addresses professional responsibilities and decisions affecting patients. Common principles include respect for autonomy, promotion of benefit, avoidance of harm, and fairness. Informed consent involves communicating relevant information and obtaining voluntary authorization from a person with decision-making capacity, subject to defined legal exceptions.
Confidentiality, accurate records, professional competence, and disclosure of conflicts of interest are central obligations. Law and regulatory institutions establish requirements for licensing, prescribing, research, and professional accountability. Medical research involving human participants is subject to ethical review and protections concerning consent, risk, privacy, and participant welfare.