首先必须了解:「主句」和「从句」是什么呢?
一个英文句子有时可细分为子句 (clause),而子句又分为主要子句 (main clause) 和从属子句 (subordinate clause),主要子句可以独立存在、表达意义,而从属子句则不能单独存在,必须依附独立子句才能构成意义。提供以下例句说明:
I saw a bird by the window when I woke up this morning.
我早上起床时,在窗边看到一只鸟。
I saw a bird by the window 为本句中的主要子句,即便没有后面的 when I woke up this morning,仍是一句有完整意思的句子,而后者则必须依附在前者之后才有意义(亦即「我今天早上起床」这个子句意思不完整),所以它就是所谓的从属子句。
对于「主句」、「从句」有了基本认识后,我们就来切入今天的主题吧!
1. While、when、as
a. 用在「主句为短暂性动作,从句为持续性动作。」在这种情境下,while 可以跟 when 和 as 替换使用。使用时,从句会使用进行式,另外,当从句在主句前面时,要加上逗号。如:
He fell asleep when/while/as he was reading.
= When/while/as he was reading, he fell asleep.
他阅读时睡着了。
主句的动词「睡着」(fell asleep)为一个短暂性动作,从句「阅读」(reading)则是持续性动作。
An apple fell to the ground when/while/as Newton was sitting under the apple tree.
牛顿坐在苹果树下时,一颗苹果掉落到地上。
补充:在此用法中,as 通常只能接有动作和发展意味的动词,不会接非进行时态的动词 (如 be、seem、love、want、agree、see、know、have)。如果出现这类动词,as 就不能取代 while,如以下例句:
A:I’m going to the post office.
我要去邮局。
B:While/When you are there, can you get me some stamps?
当你在那里时,可以帮我买几张邮票吗?
2. While
a. 用在「主句和从句皆为持续性动作,且强调主句动作延续至从句的整段时间」,while 表示「却;而」的意思。以下例句说明:
Don’t talk while you’re eating.
吃饭时不要说话。
主句的动词「说话」(talk)和从句的动词「吃饭」(eating)皆为持续性动作,本句目的在于强调前者延续至后者的整段时间。
I kept silent while he was writing.
在他写字的时候,我沉默不语。
He likes coffee, while she likes tea.
他喜欢咖啡,而她喜欢茶。
3. When/as
a. 用在「主句为持续性动作,从句为短暂性动作」,when 和 as 可通用。例句:
It was raining hard when/as we arrived.
我们到达时,正下着大雨。
主句的动词「下雨」(raining)为持续性动作,从句的动词「到达」(arrived)为短暂性动作。
Mary was singing in the room when/as a mouse fell from the ceiling.
一只老鼠从天花板掉下来时,Mary 正在房里唱歌。
b. 用在「主句和从句为两个同时(或几乎同时)发生的动作。」如:
I thought of it (just) when/as you opened your mouth.
就在你开口的时候,我也想到了。
The cat was sleeping when/as the dog was eating.
猫在睡觉的时候,狗正在吃饭。
4. When
a. 用在「每当…时」,暗示一种规律性动作。如:
It’s cold when the snow melts.
融雪时天气很冷。
He smiles when you praise him.
你夸他时他会面带微笑。
b. 用在「主句和从句动作先后发生。」如:
I will go home when he comes back.
他回来时,我就会回家。
The host will give a speech when the party begins.
派对开始时,主办人就会致辞。
c. 用在「表示一种突发状况。」如:
We were about to leave when it began to rain.
我们要离开时,突然开始下雨了。
Tom was about to board the plane when he realized he forgot to bring his cell phone .
Tom 要登机时,才发现自己忘了带手机。
5. As
a. 用在「描述两个发展中的情况」,相当于中文的「随着」。如:
Things are getting better and better as time goes by.
随着时间推移,情况日渐改善。
As it grew darker, it became colder.
随着天色暗去,天气逐渐变冷。
b. 用在「描述两件事同时进行。」如:
She sang as she walked.
她边走路边唱。
The dog ate as he wagged his tail.
狗边吃饭边摇尾巴。
以上用法都掌握了吗?下次见到 while/when/as,就不会再搞不懂了!