jocosity, hilarity, merriment, laughter, joviality, gaiety, jocundity, blitheness, jocoseness, jocularity, mirth, jollity, jolliness, glee, mirthfulness, lightheartedness, merriness, gleefulness.
The sunshine, the blithesomeness
of the morning was infectious.
If one's mind is not in accord with blithesomeness,
one surely might be excused from taking part in it."
She was vivacity itself, vivacity that never seemed noisy nor forced, just the spontaneous expression of natural blithesomeness;
and her magnetism could not be escaped.