mainspring [ˈmenˌsprɪŋ]

例句:

• You begin to understand what actions were the mainspring of the story.
  你开始体会到是什么样的行动在推动这个故事的发展。
  
• My life has been music, and a constant search for it has been the mainspring of my life.
  我以音乐为生，对音乐的不懈探索已经成为我生活的动力。
  
• Her jealousy is the mainspring of the novel's plot.
  这部小说情节中贯穿了她的忌妒之心.
  
• It is like a watch without a mainspring.
  来自NEWYORKER
• Once this 'grand alliance' was formed, Churchill became both the pivot and mainspring of it.
  来自BBC
• Modern Catalonia is among the richest regions in Spain, and its largest city, Barcelona, a mainspring of the Spanish economy.
  来自THETIMES