(n) : the emotion of great delight or happiness caused by something exceptionally good or satisfying;

: keen pleasure, elation;

: a source of keen pleasure or delight;

: something, or someone, greatly appreciated or valued …

With a definition of ‘happiness’ comes pleasure, contentment and joy. So pleasure, contentment and joy  are subsumed by the umbrella of happiness.

There is an element of the ‘extra’ in joy.

‘Joy’ is reliant, I think, on the unexpected element.

How does one ‘find’ an emotion that comes only from the existence of something that was not imagined?

Is it even possible to investigate what brings joy?