risibility

Man is the only risible animal: risibility may be said, therefore, to be his distinguishing mark.

"What is the matter," inquired Gayfield, unconscious of being the cause of their risibility.

Indeed, the Japanese have recourse to risibility whenever the frailties of human nature are put to severest test.

Mr. Maguire did not respond to the young squire's risibility; the cast of his countenance was decidedly serious.