noun (n)

• the cheerful feeling you have when nothing is troubling you(noun.feeling)

  Synonym:
  carefreeness, insouciance, lightheartedness
  

  source: wordnet30
• the gracefulness of a person or animal that is quick and nimble(noun.attribute)

  Synonym:
  agility, legerity, lightness, nimbleness
  

  source: wordnet30
• the trait of being lighthearted and frivolous(noun.attribute)

  Synonym:
  lightness
  

  source: wordnet30