The etymology of the term energy or [n-r-g], is from Greek ενέργεια, εν- means "in" and έργον means "work"; the -ια suffix forms an abstract noun. The compound εν-εργεια in Epic Greek meant "divine action" or "magical operation"; it is later used by Aristotle in a meaning of "activity, operation" or "vigour", and by Diodorus Siculus for "force of an engine."