Botany (Greek Βοτάνη - grass, fodder; Medieval Latin botanicus – herb, plant) and zoology are, historically, the core disciplines of biology whose history is closely associated with the natural sciences chemistry, physics and geology. A distinction can be made between botanical science in a pure sense, as the study of plants themselves, and botany as applied science, which studies the human use of plants. Early natural history divided pure botany into three main streams morphology-classification, anatomy and physiology – that is, external form, internal structure, and functional operation. The most obvious topics in applied botany are horticulture, forestry and agriculture although there are many others like weed science, plant pathology, floristry, pharmacognosy, economic botany and ethnobotany which lie outside modern courses in botany. Since the origin of botanical science there has been a progressive increase in the scope of the subject as technology has opened up new techniques and areas of study. Modern molecular systematics, for example, entails the principles and techniques of taxonomy, molecular biology, computer science and more.
Within botany there are a number of sub-disciplines that focus on particular plant groups, each with their own range of related studies (anatomy, morphology etc.). Included here are: phycology (algae), pteridology (ferns), bryology (mosses and liverworts) and palaeobotany (fossil plants) and their histories are treated elsewhere (see side bar). To this list can be added mycology, the study of fungi, which were once treated as plants, but are now ranked as a unique kingdom.