in·for·mant /ɪnˈfɔrmənt/
  通知者,密告者,被調查者
  In·form·ant n.
  1. One who, or that which, informs, animates, or vivifies. [Obs.]
  2. One who imparts information or instruction.
  3. One who offers an accusation; an informer. See Informer. [Obs. or R.]
  It was the last evidence of the kind; the informant
  was hanged.   --Burke.
  ◄ ►
  informant
       n 1: a person who supplies information [syn: source]
       2: someone who sees an event and reports what happened [syn: witness,
           witnesser]