Virya (potency): that which is responsible for each and every action. The substance can exert no action in absence of virya. All actions are exerted due to Virya.
asthavidha (veerya) virya – Eight qualities from the list of twenty gunas that tend to have the most prominent secondary effects on the body. They are the pairs of hot-cold, heavy-light, oily-dry, and the soft and sharp gunas. Hot and cold have the strongest effect on agni (digestive fire) and the remaining six qualities are experienced later or in a more subtle way. Vaidya Vasant Lad, Textbook of Ayurveda Volume 1, 2001: p. 300
virya - The energy or potency of a substance; the secondary action of an ingested substance, experienced after taste; two primary kinds: hot or cold.
Bodhaka agni brings forth the rasa (taste) of a substance and jathara agni its virya (potent energy). Bhuta agni creates vipaka, the post-digestive effect, in conjunction with the agni in the colon. Then pilu agni and dhatu agni take the partially digested substance and transform it into cellular material, and prabhava (unique, specific action) can occur through pithara agni. The virya of a substance has a more slow, sustained action than its rasa. It works via the media of agni and acts with vipaka through to the cellular level. Virya is responsible for digestion, absorption, and assimilation of food and yields into vipaka. Each phase of digestion is dependent on the previous phase, so without virya, vipaka is not possible. If one knows the rasa, virya, and vipaka of a food or medicinal herb, it is simple to understand its action on bodily systems. This knowledge is essential for both healing and cooking.