Happiness is an undercurrent of sensitivity and leads a surreptitious life: it is an internal eventuality. We can feel it in stillness, and it stands the test of time. Joy is an eruption of cheerful moments, and we want to express it: it is an external eventuality. We might shout it out, as it conveys a dynamic of fleeting instants. Joy gives voice to “enjoyment”. ("The grass was greener over there")