listen to the pronunciation of levity
Английский Язык - Английский Язык
lack of steadiness
lightness of manner or speech, frivolity
A lighthearted or frivolous act
The state or quality of being light, buoyancy

Hydrogen ... rises in the air on account of its levity.

{n} lightness, inconstancy, vanity, folly
lightness of manner
Lack of gravity and earnestness in deportment or character; trifling gayety; frivolity; sportiveness; vanity
The state or quality of being light,buoyancy
lightness of manner feeling an inappropriate lack of seriousness
Lack of steadiness or constancy; disposition to change; fickleness; volatility
{i} lack of seriousness, frivolity, flightiness, silliness
Levity is behaviour that shows a tendency to treat serious matters in a non-serious way. At the time, Arnold had disapproved of such levity. = frivolity. lack of respect or seriousness when you are dealing with something serious   gravity (levitas, from levis )
The quality of weighing less than something else of equal bulk; relative lightness, especially as shown by rising through, or floating upon, a contiguous substance; buoyancy; opposed to gravity
feeling an inappropriate lack of seriousness