区别不大,只是有各自的固定搭配。
1、连词immediately / directly / instantly和词组the moment, the minute意为“一……
就……”,相当于as soon as。
如: The thief ran away the moment / directly he saw the policeman。
2、immediately / directly / instantly也是副词,在句中作状语。
如: I didn’t immediately realize how serious the situation was.。
3、介词on / upon +名词 / V-ing也表示“一……就……”。
如: Yao Ming was surrounded by the media on his arrival at the airport。
On seeing the painting by Van Gogh, I fell in love with it at once。