I subscribe to a Word of the day service, and as much as I would love to say that I learn and remember all the words that are sent to me, that's not really the case. Some are just too difficult to spell or pronounce and others are simply obscure in its category and will never find their way in to my vocabulary simply because I don't talk about rocket science that often.
However, from time to time, the daily word gets my full attention and I instantly want to memorize it. The word eudemonia was of that character:
1. happiness, well-being
2. Aristotelianism. Happiness as the result of an active life governed by reason
I did some mini-research – i.e., searched for related words in my dictionary – and found this:
eudaemonism = a system of ethics that bases moral value on the likelihood that good actions will produce happiness
Remember that word, folks. Its spelling and most of all, its meaning.