toughness
  有粘性,強硬,強健
  Tough·ness, n. The quality or state of being tough.
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  toughness
       n 1: enduring strength and energy [syn: stamina, staying power]
       2: the property of being big and strong [syn: huskiness, ruggedness]
       3: the elasticity and hardness of a metal object; its ability
          to absorb considerable energy before cracking [syn: temper]
       4: impressive difficulty [syn: formidability]