1. The good life.
2. Happiness, not as a state of mind like joy, but in the sense of human flourishing.
3. The process of living well, as an end in and of itself.
Eudaimonia is a classical Greek word that comes from ‘eu’ (good or well-being) and ‘daimon’ (one’s spirit, one’s fortune). It is the good life, the life lived in harmony with one’s inner spirit, informed by thought.
The Greeks differed on the details of what this meant. For Plato, arete (virtue knowledge, ethical knowledge) was an essential part of eudaimonia: the good life is one informed by knowledge and thought. In his system, eudaimonia was proper ordering among the three competing aspects of the soul (the rational, the emotional and the appetitive), with the rational guiding desires and actions based on arete. For Aristotle, eudaimonia was a life not of honor or wealth or power, but “rational activity in accordance with virtue over a complete life” [Wiki], a combination of character virtue, intellectual virtue, friendships, scientific knowledge and more. For Epicurus, on the other hand, eudaimonia was a life of pleasure. Not simply short-term, immediate pleasure, but a thoughtful, long-term, big-picture view of pleasure in life.
More generally, eudaimonism is an ethical system where the ultimate aim and justification of activity is personal happiness. Virtuous activity is that which leads to happiness or well-being. Thus it is very distinct from utilitarian ethics wherein the virtue of an action is determined by how it affects everyone. Eudaimonism is concerned with the individual’s life, though the social and communal aspects of that life may be considered crucial to flourishing.
Nor does eudaimonism make specific prescriptions for ethical behavior that apply universally. Insofar as everyone is different, a flourishing life for those people will necessarily look different. Eudaimonia is living your life true to your individual daimon (‘spirit’, roughly), and the good life may not look the same for everyone.