noun (n)

• an earnest and sincere feeling(noun.feeling)

  Synonym:
  earnestness, seriousness
  

  source: wordnet30
• the quality of being open and truthful; not deceitful or hypocritical(noun.attribute)

  Example:
  His sincerity inspired belief.
  They demanded some proof of my sincerity.
  

  Antonym:
  falseness, hollowness, insincerity
  

  source: wordnet30
• a quality of naturalness and simplicity(noun.attribute)

  Example:
  The simple sincerity of folk songs.
  

  Synonym:
  unassumingness
  

  source: wordnet30
• the trait of being serious(noun.attribute)

  Synonym:
  earnestness, serious-mindedness, seriousness
  Antonym:
  frivolity, frivolousness
  

  source: wordnet30
• The quality or state of being sincere; honesty of mind or intention; freedom from simulation, hypocrisy, disguise, or false pretense; sincereness.(noun)

  source: webster1913