Merry, blithe, jocund, jovial, jolly mean indicating or showing high spirits or lightheartedness often in play and laughter.
Merry implies a gay, cheerful temper or mood and uninhibited enjoyment of frolic, festivity, or fun of any sort.
Blithe carries a stronger implication of freshness, buoyancy, and lightheartedness than merry; it usually suggests carefree, innocent, or even heedless gaiety.
Jocund heightens the implication of gladness and usually also connotes liveliness, exhilaration of spirits, or elation.
Jovial connotes especially good-fellowship or conviviality.
Jolly often suggests higher spirits than jovial and an even more manifest attempt to keep others laughing (as by jesting, bantering, and playing tricks).