levity

Du latin levitas (« légèreté, frivolité »).

levity \ˈlɛ.vɪ.ti\

1. (Indénombrable) Légèreté (de manières) ; nonchalance ; manque de sérieux.

   “Wouldn’t that solve your problem?” His attempt at levity earned him a growl, and Quartermaster First Class Manuel Oreza caught a warning look from the Station commander, a gray-haired warrant officer named Paul English. — (Tom Clancy, Without Remorse, 1993.)

2. (Indénombrable) Instabilité.
3. (Indénombrable) Flottabilité, légèreté.
   • Hydrogen … rises in the air on account of its levity. — (Mary Somerville, On Molecular and Microscopic Science, 1869.)
4. (Dénombrable) Frivolité ; acte frivole.
   • For though it be something wonderful to tell that any should have hearts so hardened, in the midst of such a calamity, as to rob and steal, yet certain it is that all sorts of villainies, and even levities and debaucheries, were then practiced in the town as openly as ever: I will not say quite as frequently, because the number of people were many ways lessened. — (Daniel Defoe, History of the Plague in London, 1665.)

• gravity