Meaning : The trait of acting unpredictably and more from whim or caprice than from reason or judgment.
Example :
I despair at the flightiness and whimsicality of my memory.
Synonyms : arbitrariness, capriciousness, flightiness, whimsey, whimsy
Meaning : The trait of behaving like an imp.
Synonyms : impishness, mischievousness, puckishness