Energeia is a word based upon ἔργον (ergon), meaning 'work'. It is the source of the modern word 'energy' but the term has evolved so much over the course of the history of science that reference to the modern term is not very helpful in understanding the original as used by Aristotle. It is difficult to translate his use of energeia into English with consistency. Joe Sachs renders it with the phrase 'being–at–work' and says that "we might construct the word is-at-work-ness from Anglo-Saxon roots to translate energeia into English". Aristotle says the word can be made clear by looking at examples rather than trying to find a definition. Two examples of energeia in Aristotle's works are pleasure and happiness (eudaimonia). Pleasure is an energeia of the human body and mind whereas happiness is more simply the energeia of a human being a human.

I'm not sure this helps much. 

Also a Soviet rocket, designed to carry the space shuttles of the Buran programme.

Source: https://en.wikipedia.org/wiki/Potentiality_and_actuality#Energeia 

(✂︎ From the ongoing #JoDoesPhD words I googled this week series)