tenuous         
adjective uk/ˈten.ju.əs/ us/ˈten.ju.əs/
 (关系、想法、形势等)不确定的,不明朗的
A tenuous connection, idea, or situation is weak and possibly does not exist.
  The police have only found a tenuous connection between the two robberies. 我们只能认定这两桩抢劫案之间可能有某些联系。 
  literary纤细的;单薄的;脆弱的 
thin, weak, and easily broken