This chapter is devoted to nomenclature: systematically formulated names for specific entities. Biological nomenclature dates back at least to the 18th century. Since the mid-20th century, many biomedical disciplines have established committees to develop and promulgate official systems of nomenclature. Accelerating knowledge, particularly from molecular biology, necessitated the official biomedical nomenclature systems, sometimes with dramatic results. For instance, a single coagulation factor had been referred to by 14 different names...