What a mess trying to sort through in English what Aristotle actually meant by “actuality.” Turns out he used two words, energeia and entelechia and these have been both translated in Latinized translations as actuality. Which is not helpful sorting through the difference. Joe Sachs translates them as “being-at-work” and “being-at-work-staying-itself,” respectively. His translation conveys the philosophical action of the work, but makes for awkward translation. My guess is that in de Anima, his book on the soul, entelechia represents gradations of more or less completed or perfect energeia. I will correct this post if anyone who knows better tells me I’ve got the relation wrong.