Happiness is a contested concept; different traditions emphasize different elements. Here are the main philosophical and psychological definitions, plus a concise working definition.

• Hedonic: happiness = pleasure and absence of pain (Epicurus; modern hedonism).
• Eudaimonic: happiness = flourishing or living well through virtue and realizing human capacities (Aristotle, Nicomachean Ethics).
• Utilitarian: happiness = the aggregate pleasure or welfare that should guide moral action (Jeremy Bentham, John Stuart Mill).
• Stoic: happiness = inner tranquility achieved by living according to reason and virtue, independent of externals (Epictetus, Marcus Aurelius).
• Buddhist: happiness = freedom from craving and suffering; a peace that arises from insight and ethical practice (Dhammapada; Buddhist teachings).
• Psychological (contemporary): happiness often measured as subjective well‑being — life satisfaction plus frequent positive affect and infrequent negative affect — and as psychological well‑being involving meaning, autonomy, mastery, and relationships (Diener; Ryff; Seligman).

Working definition (integrative, practical):
Happiness = a relatively stable state of well‑being characterized by frequent positive experience, meaningful engagement, and the cultivation of capacities and relationships that enable flourishing and resilience in the face of hardship.

Notes:

• Distinguish fleeting pleasure from durable flourishing; both matter but play different roles.
• How you define happiness affects what you pursue and value (pleasure, virtue, meaning, or social welfare).

Selected sources for further reading:

• Aristotle, Nicomachean Ethics.
• Epicurus, Letter to Menoeceus.
• John Stuart Mill, Utilitarianism.
• Diener, E. (1984). “Subjective Well‑Being.”
• Ryff, C. (1989). “Happiness is…”: Psychological Well‑Being.
• Seligman, M. E. P. (2011). Flourish.