levity

noun, plural lev·i·ties.

1. lightness of mind, character, or behavior; lack of appropriate seriousness or earnestness.
2. an instance or exhibition of this.
3. fickleness.
4. lightness in weight.

noun plural -ties

1. inappropriate lack of seriousness
2. fickleness or instability
3. archaic lightness in weight

n.“want of seriousness, frivolity,” 1560s, from Latin levitatem (nominative levitas) “lightness, frivolity,” from levis “light” in weight (see lever) + -ity.