Internal medicine or general medicine (in Commonwealth nations) is the medical specialty dealing with the prevention, diagnosis, and treatment of adult diseases. Physicians specializing in internal medicine are called internists, or physicians (without a modifier) in Commonwealth nations. Internists are skilled in the management of patients who have undifferentiated or multi-system disease processes. Internists care for hospitalized and ambulatory patients and may play a major role in teaching and research. Internal medicine or general medicine (in Commonwealth nations) is the medical specialty dealing with the prevention, diagnosis, and treatment of adult diseases. Physicians specializing in internal medicine are called internists, or physicians (without a modifier) in Commonwealth nations. Internists are skilled in the management of patients who have undifferentiated or multi-system disease processes. Internists care for hospitalized and ambulatory patients and may play a major role in teaching and research. Because internal medicine patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. Internists often have subspecialty interests in diseases affecting particular organs or organ systems. Internal medicine is also a specialty within clinical pharmacy and veterinary medicine. The etymology of the term internal medicine in English is rooted in the German term Innere Medizin from the 19th century. Internal medicine delved into underlying pathological causes of symptoms and syndromes by use of laboratory investigations in addition to bedside clinical assessment of patients. In contrast, physicians in previous generations, such as the 17th-century physician Thomas Sydenham, who is known as the father of English medicine or 'the English Hippocrates', had developed nosology (the study of diseases) via the clinical approach to diagnosis and management, by careful bedside study of the natural history of diseases and their treatment. Sydenham eschewed dissection of corpses and scrutiny of the internal workings of the body, for considering the internal mechanisms and causes of symptoms. It was thus subsequent to the 17th century that there was a rise in anatomical pathology and laboratory studies, with Giovanni Battista Morgagni, an Italian anatomist of the 18th century, being considered the father of anatomical pathology. Laboratory investigations became increasingly significant, with contribution of doctors including German physician and bacteriologist Robert Koch in the 19th century. The 19th century saw the rise of internal medicine that combined the clinical approach with use of investigations. Many early-20th century American physicians studied medicine in Germany and brought this medical field to the United States. Thus, the name 'internal medicine' was adopted in imitation of the existing German term. Historically, some of the oldest traces of internal medicine can be traced from Ancient India and Ancient China. Earliest texts about internal medicine are the Ayurvedic anthologies of Charaka. Internal medicine specialists, also known as general internal medicine specialists or general medicine physicians in Commonwealth countries, are specialist physicians trained to manage particularly complex or multisystem disease conditions that single-organ-disease specialists may not be trained to deal with. They may be asked to tackle undifferentiated presentations that cannot be easily fitted within the expertise of a single-organ specialty, such as dyspnoea, fatigue, weight loss, chest pain, confusion or change in conscious state. They may manage serious acute illnesses that affect multiple organ systems at the same time in a single patient, and they may manage multiple chronic diseases or 'comorbidities' that a single patient may have. General internal medicine specialists do not provide necessarily less expertise than single-organ specialists, rather, they are trained for a specific role of caring for patients with multiple simultaneous problems or complex comorbidities. Perhaps because it is complex to explain treatment of diseases that are not localised to a single-organ, there has been confusion about the meaning of internal medicine and the role of an 'internist.' Internists are qualified physicians with postgraduate training in internal medicine and should not be confused with 'interns', who are doctors in their first year of residency training (officially the term intern is no longer in use). Although internists may act as primary care physicians, they are not 'family physicians,' 'family practitioners,' or 'general practitioners,' whose training is not solely concentrated on adults and may include surgery, obstetrics, and pediatrics. The American College of Physicians defines internists as 'physicians who specialize in the prevention, detection and treatment of illnesses in adults'. Internal medicine physicians have practiced both in clinics and in hospitals, often in the same day. Pressures on time have led to many internal medicine physicians to choose one practice setting, who may choose to practice only in the hospital, as a 'hospitalist', or only in an outpatient clinic, as a primary care physician.