noun (n)

• a flaw or weak point(noun.state)

  Synonym:
  failing
  

  source: wordnet30
• powerlessness revealed by an inability to act(noun.attribute)

  Example:
  In spite of their weakness the group remains active.
  

  Synonym:
  helplessness, impuissance
  

  source: wordnet30
• the property of lacking physical or mental strength; liability to failure under pressure or stress or strain(noun.attribute)

  Example:
  His weakness increased as he became older.
  The weakness of the span was overlooked until it collapsed.
  

  Antonym:
  strength
  

  source: wordnet30
• the condition of being financially weak(noun.state)

  Example:
  The weakness of the dollar against the yen.
  

  source: wordnet30
• a penchant for something even though it might not be good for you(noun.feeling)

  Example:
  He has a weakness for chocolate.
  

  source: wordnet30
• The quality or state of being weak; want of strength or firmness; lack of vigor; want of resolution or of moral strength; feebleness.(noun)

  source: webster1913