Happiness is a positive and pleasant emotion, ranging from contentment to intense joy. Moments of happiness may be triggered by positive life experiences or thoughts, but sometimes it may arise from no obvious cause. The level of happiness for longer periods of time is more strongly correlated with levels of life satisfaction, subjective well-being, flourishing and eudaimonia. In common usage, the word happy can be an appraisal of those measures themselves or as a shorthand for a "source" of happiness. As with any emotion, the precise definition of happiness has been a perennial debate in philosophy.

Emotions are physical and mental states brought on by neurophysiological changes, variously associated with thoughts, feelings, behavioral responses, and a degree of pleasure or displeasure. There is no scientific consensus on a definition. Emotions are often intertwined with mood, temperament, personality, disposition, or creativity.