A nosological unit is a separate disease or pathological condition that has specific characteristics and differs from other diseases.
A nosological unit is characterized by certain manifestations, course, outcome and causes of development. Each nosological unit has clear diagnostic criteria that allow it to be distinguished from other diseases.
Nosological units are classified according to etiology, pathogenesis, localization of the pathological process, clinical manifestations and other signs.
The description of nosological units is the subject of the study of nosology - a branch of medicine that deals with the systematization and classification of diseases.
Thus, a nosological unit is a clearly defined disease with specific characteristics that allow it to be differentiated from other diseases.