Introduction of dravya Chapter 9 of Ashtanga Hridayam (Dravadravyavijnaniya ) lays the foundation of Ayurvedic pharmacology: what a dravya (substance) is, how its qualities (guṇa) and tastes (rasa) act on the body, and how these properties determine therapeutic use. This chapter explains the classical framework— panchamahabhuta basis, rasa, virya, vipaka, guṇa, and prabhava , element‑based qualities, guṇa , vīrya , vipāka , karma‑vidhāna , prabhāva , and vichitra pratyayārabdha dravya —and shows how to choose, combine, and dose substances for clinical effect. READ ALSO: DRAVYA Core concepts and their clinical meaning Dravya (substance): any material used as food, medicine, or vehicle; studied for its inherent and emergent effects. Rasa (taste): the first sensory property that interacts with the tongue and begins physiological response; six classical rasas influence doshas and dhatus. Virya (potency/energetics): the hot or cold action of a substance that de...