Veerya is specially considered as a separate and important entity in Ayurveda. The potency of a dravya which enables the dravya to show its action is known as Veerya. It is considered as the active principle of a dravya. Actually it is the ultra chemical action of the drugs. It may be of two types Ushna (hot) and Shita (cold). Their translation as hot or cold is not appropriate as these denote only to the temperature status, while the veerya is something more than that. Veerya is given prime importance in classics as this decides the karma. If the dravya becomes nirveerya, then the dravya is useless. So veerya (potency) of drug plays vital role in treatment principles. Shirisha which is isad ushna dravya is tested for its potency. So to scrutinize the potency of the drug exothermic and endothermic reactions play imperative role.