nosos

Nosos (νόσος) is a Greek noun meaning disease or illness. In ancient Greek medical and literary usage, nosos referred to any condition impairing health, ranging from physical sickness to malaise of mind. The term is the etymological source of a large group of modern medical words built around disease and its study, including the common English combining form noso-.

In modern medical terminology, noso- appears in terms such as nosology, the branch of medicine that classifies diseases, and nosography, the description or recording of diseases and their signs. The word has also contributed to terms describing disease origins or behavior, and it is encountered in scholarly discussions of pathology and clinical taxonomy.

Historically, Greek writers used nosos within naturalistic explanations of illness. While early Greek medicine connected disease to humoral balances and environmental factors, the word itself signified sickness as a health condition rather than a purely supernatural affliction. With later medical advances, nosos became a foundational root for systematic disease classification in Western medicine.

Related terms include nosocomial, meaning hospital-acquired disease, derived from nosos via the Greek word nosokomeion for hospital. Other derivatives include nosology, nosography, and, less commonly, nosotherapy and nosodiagnosis. The root remains in contemporary medical language as part of the vocabulary for diagnosing, describing, and categorizing disease.