初中生应掌握的连词英语，剑桥MSE丨As，when

As, when和while均为连接词，但是某些情况下，三者也会有略微的差别。

今天王老师就为大家分享下As, when和while的具体用法~

As, when or while

我们可以用as, when和while来表示“当...时”，来连接同时发生的两个事件:

Another family arrived as we were leaving.

When my father was out working in the field, I helped with milking the cows, feeding the pigs.

我们也可以用as, when和while 过去进行时，用来表示背景事件:

As she was leaving the court, a crowd of photographers gathered around her.

Steven was very unhappy when things weren't going well for him.

As

我们用as连接发生在同一时间的两件事情。As后可以使用过去时/过去进行时，使用过去进行时更加强调其中一件事打断了另一件事，or在另一件事正在进行的过程中发生。

As she walked to the door, she thanked them for a lovely dinner.

As they were signing the contract, they noticed that a page was missing.

When

我们可以使用when来引入在一个较长事件中间发生的单个的、已完成的事件。在这种用发下，我们通常在主句中使用进行时来描述较长的背景事件:

He was walking back to his flat when he heard an explosion.

根据上下文，when既可以表示“after”的意思，也可以表示“at the same time”的意思：

When（=After）you open the file, check the second page.

I eat popcorn when I am watching TV. （=at the same time）

我们常用just和when连用来表达事情在同一瞬间发生:

The phone always rings just when I'm closing the front door.

While

我们通常用while连接两个同时发生的事件，且这两个事件持续时间较长：

We spent long evenings talking in my sitting-room while he played the music he had chosen and explained his ideas.

We were lying on the beach sunbathing while they were playing volleyball.

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