imperceptibly [ˌɪmpɚˈsɛptəblɪ]

例句:

• New problems arose imperceptibly.
  不知不觉地出现了一些新问题.
  
• Imperceptibly, the boat had slowly turned.
  船慢慢地在转弯, 简直使人不觉得.
  
• Time fled, and she was surprised to find the year passed imperceptibly.
  光阴飞逝, 她诧异地发觉一年不知不觉就过去了.
  
• The concerto's opening is notable because the piano enters almost imperceptibly.
  来自WSJ
• Meanwhile, the earth warmed imperceptibly; glaciers plunged into the sea.
  来自NEWYORKER
• On "You Got Me Up" chimes segue imperceptibly into electronic bleeps.
  来自BBC