noun (n)

• lack of an adequate quantity or number(noun.attribute)

  Example:
  The inadequacy of unemployment benefits.
  

  Synonym:
  deficiency, insufficiency
  Antonym:
  adequacy, sufficiency
  

  source: wordnet30
• a lack of competence(noun.state)

  Example:
  Juvenile offenses often reflect an inadequacy in the parents.
  

  Synonym:
  insufficiency
  

  source: wordnet30
• unsatisfactoriness by virtue of being inadequate(noun.attribute)

  Synonym:
  inadequateness
  Antonym:
  adequacy, adequateness
  

  source: wordnet30
• The quality or state of being inadequate or insufficient; defectiveness; insufficiency; inadequateness.(noun)

  source: webster1913