noun (n)

• a manner that does not take forms and ceremonies seriously(noun.attribute)

  Antonym:
  formality, formalness
  

  source: wordnet30
• freedom from constraint or embarrassment(noun.attribute)

  Synonym:
  ease
  

  source: wordnet30
• The state of being informal; want of regular, prescribed, or customary form; as, the informality of legal proceedings.(noun)

  source: webster1913