WordRel.com

• the quality of being open and truthful; not deceitful or hypocritical

  antonym	insincerity
  derivation	sincere
  attribute	insinceresincere
  hypernym	truthfulness
  hyponym	heartinesssinglenessstraightforwardnesswholeheartedness

• the trait of being serious

  synonym	earnestnessserious-mindednessseriousness
  derivation	sincere
  attribute	frivolousserious
  hypernym	trait
  hyponym	commitmentcommittednessgravenessgravitysedatenesssobernesssobrietysolemnesssolemnitysombernesssombrenessstaidness

• a quality of naturalness and simplicity

  synonym	unassumingness
  hypernym	naturalness

• an earnest and sincere feeling

  synonym	earnestnessseriousness
  derivation	sincere
  hypernym	gravitysolemnity