Muditā (Pāli and Sanskrit: मुदिता) in Buddhism is joy. It is especially sympathetic or vicarious joy, the pleasure that comes from delighting in other people’s well-being rather than begrudging it.
Mudita meditation is used to cultivate appreciative joy at the success and good fortune of others. It is used to counteract the resentment, jealousy, or envy often experienced at another’s success.
Many Buddhist teachers interpret joy more broadly as an inner spring of infinite joy that is available to everyone at all times, regardless of circumstances. The more deeply one drinks of this spring, the more secure one becomes in one’s own abundant happiness, and the easier it then becomes to relish the joy of other people as well.
Joy is also traditionally regarded as the most difficult to cultivate of the four immeasurables (brahmavihārā: also “four sublime attitudes”). To show joy is to celebrate happiness and achievement in others even when we are facing tragedy ourselves.