Pharmacology (pharmakon, a drug, logos a discourse) is a convenient term for the whole subject of Materia Medica, pharmacy and medicinal therapeutics. Specifically, it refers often to drug effects, as evinced from experiments on animals, and as such is the only source of modern old-school knowledge of the physiological action of drugs.

Materia Medica is the study of drugs in regard to their origin, physical and chemical properties, but especially and chiefly in regard to their effects in modifying the health of the body. The latter is the distinctive field of the Homoeopathic Materia Medica.