Time period from 1901 through 2000 of the common era.
Time period from 1801 through 1900 of the common era.
The period of history before 500 of the common era.
A former branch of knowledge embracing the study, description, and classification of natural objects (as animals, plants, and minerals) and thus including the modern sciences of zoology, botany, and mineralogy insofar as they existed at that time. In the 17th, 18th, and 19th centuries it was much used for the generalized pursuit of certain areas of science. (Webster, 3d ed; from Dr. James H. Cassedy, NLM History of Medicine Division)