soon, at once
这两个词(组)的区别是:soon表示“不久”“很快”,强调时间很短; at once表示“马上”“立刻”,强调动作随即发生。例如:
He soon became active in the class.他在班上很快就变得活跃起来。
When I heard the knock,I opened the door of the room at once.我听到敲门声马上就把房门打开了。
as soon as, no sooner...than, hardly...when
这三个短语都可表示“一…就…”。它们的区别是：
1.as soon as可转化为no sooner...than或hardly...when结构。例如:
As soon as I heard the knock I opened the door.
No sooner had I heard the knock than I opened the door.
Hardly had I heard the knock when I opened the door.
当我听到敲门声,我马上就开门了。
2.as soon as通常用于一般时态, no hardly...than和hardly...when通常用于过去完成时。例如:
As soon as you finish your job, let me know.你一完成工作就告诉我一声。
No sooner had the doctor arrived than he began treating the sick.医生一到马上就抢救病人。
I had hardly started when it began to rain.我刚动身就下起雨来了。
soon, fast, quickly
这三个词都可表示“很快”。它们的区别是：
soon强调的是预期的时刻不久就会到来, fast和quickly强调的是动作进行的速度快。例如:
Their population is growing fast.他们的人口增长得很快。
Come quickly, he's drowning!快来,他溺水了。
soon, early, quick, shortly
这组词共同的意思是“不久”“即刻”“快”。它们的区别在于:early常指时间比原来或通常早些; quick含有匆忙、仓促之意; soon指在某一特定时间过现在之后不久,多用于将来时或过去时,通常放在句末或主要动词之前; shortly与soon同义,但比soon更郑重,常用于新闻报道等。例如:
You have to think quick with the mind and act quick with the body.你必须脑子转得快,行动也得快。
I came early, and had to wait for others, but soon after five o'clock they appeared.我来得早,得等其他人,可是刚过5点他们就都来了。
Shortly after that, the police arrived.那事情发生不久警察就到了。
how soon, how long
这两个短语的区别是:how soon的意思是“多久”,当我们就陈述句中的“过多少时间(就能…)”这一部分提问时,只能用how soon不能用how long; how long的意思是“多长”,当我们就陈述的“一段时间的长短”提问时,要用how long,不能用how soon。试比较:
“How soon will he be here?”“In two hours.” “再过多久他就在这里了?”“两个小时。” “How long will he be here?”“For two hours.” “他要在这里呆多长时间?”“两个小时。”
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。
