Happiness is used in the context of mental or emotional states, including positive or pleasant emotions ranging from contentment to intense joy. It is also used in the context of life satisfaction, subjective well-being, eudaimonia, flourishing and well-being.

Since the 1960s, happiness research has been conducted in a wide variety of scientific disciplines, including gerontology, social psychology, clinical and medical research and happiness economics.

‘Happiness’ is the subject of debate on usage and meaning and on possible differences in understanding by culture.

The word is used in several related areas: current experience, including (a) the feeling of an emotion (affect) such as pleasure or joy, or (b) a more general sense of ‘emotional condition as a whole’. For instance Daniel Kahneman has defined happiness as “what I experience here and now”. This usage is prevalent in dictionary definitions of happiness.

The implied meaning of the word may vary depending on context, qualifying happiness as a polyseme and a fuzzy concept.

Some users accept these issues, but continue to use the word because of its convening power.