noun (n)

• the state of being weak in health or body (especially from old age)(noun.state)

  Synonym:
  debility, frailness, frailty, infirmity, valetudinarianism
  

  source: wordnet30
• the quality of lacking intensity or substance(noun.attribute)

  Synonym:
  tenuity
  

  source: wordnet30
• The quality or condition of being feeble; debility; infirmity.(noun)

  source: webster1913