when while since until的区别？

when while since until的区别？

（1）when.①当…的时候，when 从句谓语动词可为延续性动词或非延续性动词。Eg. I was listening to MP3 when my friend arrived. Eg. When I was young, I would go hunting with my father in the forest. ②when可作并列连词，连接两分句，意为“就在/刚好那时”。Eg. Jim was on holiday with his mother in a wildlife park when a poisonous snake bit him.

(2)while.①在…的时候。注意while从句须用延续性动词。Eg. While I was sweeping the floor, Mr. Zhou walked in. eg. _______she left her hometown, it was snowing hard. A. When B. while C. after

②while可作并列连词，表示比较或对比。意为“而/却/可是”

eg. Mother often takes a bus to work______Father usually goes by car.

Eg. We Chinese like using chopsticks______westerners prefer knives and forks.

A.when B. while C. because D. since E. that

(3) ①before.在…之前。主句谓语动词先于从句的谓语动作之前。②before 还有其它的意思“还要过多少时间/过了多少时间才…”

eg. He covered not more than 5 miles______it began to rain heavily.

Eg. Ten years had passed______he realized he hadn’t learned much.

Eg. It won’t be long_____Mother returns home.

Eg. The boy was run over by the train_____she could save him.
A. after B. before C. when D. since E. until

(4)till/until. “直到…”后面不能接地点名词。①可作介词，后跟时间点。②也可以作连词，引导时间状语从句。③till 和until 可互换，但是从句位于句首时只能用until. ④not…until. “直到…才…”。如果主句的谓语动词为非延续性动词，主句应当用否定式。

eg. _____the sunset, they didn’t leave their workplace.(till/until)

eg. The bus stopped until it pulled in.(改错)

注：not until 置于句首时引起倒装， 其结构为：not until…+ 主句部分倒装。

（5）since. 自从…以来。①since + 时间点 ②since + 时间状语从句 ③含since 引导的时间状语从句的复合句，主句用现在完成时，since从句用一般过去时。④注意以下句式： It is/has been + 时间段 + since 从句. 如果since 从句的谓语动词为非延续性动词，该句式表示这动作或状态已持续了多久；如果since从句的谓语动词为延续性动词，则表示该动作已终止了多久。Eg. It is three years since he began to teach in our school.他在我们学校已经教了三年书。Eg. It is three years since the Greens lived here.格林夫妇三年前从这里搬走了。⑤since 与before的区别：A. since 的主句用现在完成时，而since从句用一般过去时。Eg. The Grees have lived here since they move to this little town. B. before 用法：主句（一般将来时） + before +从句（一般现在时）；主句（过去时态） + before + 从句（一般过去时）

eg. It will be three months before he comes back. 还有三个月他才会回来。

Eg. The boy was run over before she could rush to save him. 他还未来得及冲过去救那个还子，车子就已经从孩子身上碾过了

when一前一后 while 同时发生 since引导时间,原因状语从句,, until直到...是连词

when什么时间 疑问词
while当……时，前接现在进行时，后接过去进行时
since自从
until直到