instantly

immediately, instantly, presently, directly, shortly, soon, at once, right away

这些副词或副词词组均有“立刻、马上”之意。
immediately: 指做完一件事后，立即就做另一件事，中间一般没有明显的时间间隔。
instantly: 指恰恰就在此刻，一秒钟也没耽误。
presently: 指不久、即将。
directly: 和immediately同义，指毫无迟疑。
shortly: 和soon同义，指动作发生或完成的速度之快。
soon: 常用词，指行动快，完成速度快。
at once: 口语中常用，语气强烈，指时间紧迫，一刻也不能耽误。
right away: 主要用于美国英语，语气稍弱于at once，强调动作迅速。

副词 instantly:

1. without delay or hesitation; with no time intervening
   同义词：immediately, straightaway, straight off, directly, now, right away, at once, forthwith, in real time, like a shot
2. without any delay
   同义词：instantaneously, outright, in a flash

1. Gas flowing through the pipes burns instantly but can be kept under control easily by opening or closing the pipes.
   通过管子的煤气会瞬间燃烧起来，但我们凭开、关管道很容易控制它。
2. The poor girl was dismissed instantly.
   这个可怜的姑娘被当即解雇。
3. It's an instantly recognizable face.
   那是我一眼就能认得出的面孔。
4. Please tell me instantly he arrives.
   他一到就请告诉我。