lev·i·ty 
(lĕvĭ-tē)
(lĕvĭ-tē)n. pl. lev·i·ties
1. Humor, merriment, or a lack of seriousness, especially when inappropriate: a subject that should not be treated with levity.
2. Archaic Inconstancy; changeableness.
3. Archaic The state or quality of being light; buoyancy.
[Latin levitās, from levis, light; see legwh- in the Appendix of Indo-European roots.]