(also called Power).— A capacity for act, whether entitative or operative. 

Active Potency (also called Active Power).— A capacity to act upon another. E.g., a pianist’s capacity to play the piano. 

Passive Potency (also called Passive Power).— A capacity to be acted upon by another. E.g., a piano’s capacity to be played. 

Obediential Potency.— A passive potency in a creature that can only be actualized by a higher agent.  The notion of obedient potency is important for understanding, instrumental causality, miracles, the relationship between the natural and supernatural orders, and salvation.