七年级上册英语语法：比较until和till

　　比较until跟till
 
这两个连词意思相同。七年级上册英语语法讲解肯定句表示的意思是"做某事直至某时"，动词必须是连续性的。否定形式表白的意思是"直至某时才做某事"。动词为延续性或非持续性都可以。 正确利用这两个连词的关键之一就在于判断句中的动词该用肯定式还是否定式。

　
确定句例句：
I slept until midnight. 我始终睡到深夜时醒了。
Wait till I call you.　 等着我叫你。
（七年级上册英语语法注意在肯定句中可用before代替 Let's get in the wheat before the sun sets.）

否定句例句：
She didn't arrive until 6 o'clock.
她直到6点才到。
Don't get off the bus until it has stopped.
公共汽车停稳后再下车。
I didn't manage to do it until you had explained how.　 直到你教我后，我才会做。

内容来自

1)Until可用于句首，而till通常不用于句首。
Until you told me, I had heard nothing of what happened.
直到你告诉我以前，出了什么事我一点也不晓得。　
2)Until when 疑难句中，until要放在句首的七年级英语语法。
---Until when are you staying 　你呆到什么时候 
--- Until next Monday.　呆到下周一。　

留心：否认句可用另外两种句式表现。
(1）Not until …在句首，主句用倒装。
Not until the early years of the 19th century did man know what heat is.
直到19 世纪初，人类才知道热能是什么。
Not until I began to work did I realize how much time I had wasted.
直到我开始工作，我才意识到了我已蹉跎了多少多岁月。
(2)　It is not until… that… 七年级英语语法固定搭配词组。

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