Until 直….止,not… until直…才
肯定形式表示意思"做某事直至某時"動詞必須延續(xù)性
否定形式表達(dá)意思"直至某時才做某事"動詞延續(xù)性或非延續(xù)性都 可以
肯定句：
I slept until midnight.我一直睡到半夜時才醒了 .
Wait till I call you.等著我叫 你.
（肯定句用before代替,Lets get in the wheat before the sun sets.）
否定句：
She didnt arrive until 6 oclock.
直6點(diǎn)她才 到.
Dont get off the bus until it has stopped.
公共汽車停穩(wěn)再下車 .
I didnt manage to do it until you had explained how.直到你教會我我才會做 .
否定句用另外兩種句式表示 ：
(1)Not until …句首主句用倒裝
Not until the early years of the 19th century did man know what heat is.
直19 世紀(jì)初人類才知道熱能是什么.
Not until I began to work did I realize how much time I had wasted.
直我開始工作我才認(rèn)識到我已蹉跎了幾多歲月 .
(2) It is not until… that…這是一個強(qiáng)調(diào)結(jié)構(gòu).如本題
Till用法基本相同
1)Until用于句首而till通常不用于句首
Until you told me,I had heard nothing of what happened.
直到你告訴我以前,出了什么事我一點(diǎn)也不知道 .
2)Until when 疑問句until要放句首
---Until when are you staying?你呆到什么時候
--- Until next Monday.呆到下周一.