pre·cur·sor /prɪˈkɝsɚ/
  先驅者,前導,先進者
  pre·cur·sor /prɪˈkɝsɚ, ˈprɪˌ/ 名詞
  前身,前體,先質,產物母體(化合物)
  Pre·cur·sor n.  One who, or that which, precedes an event, and indicates its approach; a forerunner; a harbinger.
     Evil thoughts are the invisible, airy precursors of all the storms and tempests of the soul.   --Buckminster.
  Syn: -- Predecessor; forerunner; harbinger; messenger; omen; sign.
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  precursor
       n 1: a substance from which another substance is formed
            (especially by a metabolic reaction)
       2: a person who goes before or announces the coming of another
          [syn: forerunner]
       3: an indication of the approach of something or someone [syn:
          harbinger, forerunner, herald]