Pronation derives from prone ... lying down on your face. Thus pronation is the act of turning face down (e.g. putting your palm down on a table) Supination is the opposite act.
An example of forearm pronation is turning your palm down to pour liquid out of container.
An example of forearm supination is turning your palm up to catch a snowflake in your hand.
Supination is a position of either the forearm or foot; in the forearm when the palm faces anteriorly, or faces up while pronation refers to the inward roll of the foot during normal motion and...