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Until的用法
1. prep. up to a specified time (直到某一时刻)或up to the time of a specified event (直到发生某事)
2. conj. up to the time when (直到……时为止)
用于肯定句中：
表示主句的动作一直持续到until短语所表示的时间或从句动作发生或状态出现时为止，即表示动作的终点。一般可译为“直到……时(为止)”或“在……以前”。在这种用法中，句子的谓语动词必须是持续动词(非瞬间动词)，如live, wait , last, love, like, stay, work, continue 等。
1) It may last until Friday. 这可能要延续到星期五。
2) He will be working until 5 o'clock. 他将一直工作到五点钟。
3) She was a bank clerk until the war, when she trained as a nurse. 她战前是个银行职员，战时受训当了护士。
4) I have remembered her until now. 直到现在我还记得她。
5) Continue in this direction until you see a sign. 一直朝着这个方向走就会看见指示牌了。 6) He ran until he was breathless. 他一直跑到气喘吁吁才停下。
7) I'll wait until he arrives and then I'll leave. 我要等他来以后再离开。 8) Go straight on until you come to a large red building. 一直往前，走到一幢高大的红色建筑物为止。
9) Let's wait until the rain stops. 咱们等雨停吧。
10) The teacher kept on asking the students questions until the bell rang. 老师反复向学生提问，直到下课铃响。
用于否定句中：
表示主句的动作直到until短语所表示的时间或在从句的动作发生之后才开始发生，也即是主句的动作在until短语所表示的时间或在从句的动作发生之前尚未发生。表示动作的起点。动词为延续性或非延续性都可以。 一般译为“直到……才”或“直到……之前(……还不)”。 1) The secret was never told until after the old man's death. 这个秘密在老人去世后才说出来。 2) Don't open it until your birthday. 等到你过生日那天再打开。 3) She didn't sleep until eight. 她八点钟才睡觉。
4) I hadn't realized she was foreign until she spoke. 她不说话我还一直不知道她是个外国人。 5) I won't stop shouting until you let me go. 你不放我，我就一直喊叫。 6) I shan't do that until you come back. 在你回来之前，我不会干那件事。
7) We won't come to any decision until we have had a chance to discuss the problem thoroughly.我们有机会充分讨论这个问题再决定下来。
8) Until you told me I had no idea of it. 在你告诉我之前，我对此一无所知。
not until的倒装与强调结构
1. 当Not until位于句首时,句子要倒装。其结构为: Not until + 从句/表时间的词 + 助动词
+ (主句)主语 + 谓语 + ...。如:
1) The students did not stop talking until the teacher came in. →
Not until the teacher came in did the students stop talking. 直到老师进来学生们才停止讲话。
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2) The sports meeting will not be held until next week. →
Not until next week will the sports meeting be held.直到下周才开运动会。 3) Man did not know what heat is until the early years of the 19th century. →
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。
4) I did not realize how much time I had wasted until I began to work. →
Not until I began to work did I realize how much time I had wasted. 直到我开始工作，我才认识到了我已蹉跎了几多岁月。
2. not until 强调结构为:It is / was not until + 从句/表时间的词 + that + ...。上面两句改为
强调句为:
1) It was not until the teacher came in that the students stopped talking. 2) It is not until next week that the sports meet will be held.
3) It was not until the early years of the 19th century that man knew what heat is. 4) It was not until I began to work that I realized how much time I had wasted.
Until和till, by, before的区别：
1. until和till区别
until是till的强调形式，但是它们表达的意义是相同的，都表示\直到某时\。 He waits until / till the children are asleep. 他等着直到孩子们睡熟。
I shall stay here until / till twelve o'clock. 我将留在这里一直到十二点钟。 He didn't come until / till late in the morning. 他直到早上很迟才来。 He didn't arrive until / till the game had begun. 直到比赛开始他才到。
注意：主句为一般将来时，until / till引导的从句用一般现在时代替将来时。例如： He couldn't ride until / till he was fifteen years old. 他直到十五岁才会骑自行车。
1) 用于“It is / was not until...that”或含有“not...until...”的强调结构中，其中的until
不能改为till。
It was not until the film had begun that he arrived. 直到电影开始他才到。 It is not until 8:00 that we begin our class every day. 我们每天八点开始上课。 2) Not until放在句首时，句子要倒装，其中的until不能改为till。
Not until the last moment did he change his mind. 直到最后一刻他才改变主意。 Not until midnight did it stop raining. 直到午夜雨才停。 3) 句首通常只用until，不用till。
Until then, I knew nothing at all about it. 在那之前，我对此事一无所知。 Until you told me I had no idea of it. 在你告诉我之前，我对此一无所知。 4) 某些固定词组或谚语中通常只用till。
from morning till night 从早到晚。 up till now直到现在。
2. until和by的区别
1) by表示在某特定的时间之前或不迟于某特定的时间,意为\最迟在;不迟于\或\
在……之前\等。
I will finish my task by nine. 我将在九点钟前完成任务。
The plane takes off at 10:00, so you must try to be at the airport by 9:30. 飞机在十点钟起飞,所以你必须在九点半赶到机场。
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2) until用在肯定句,谓语动词通常是延续性动词,如stand, stay, talk, wait等,表示主句动
作终止的时间。
I waited until he came back.我一直等到他回来。 The war lasted until 1945.战争持续到1945年。
如果用在否定句,谓语动词通常是瞬间性动词,如open, start, leave, arrive, finish, stop等,强调主句动作开始的时间。
I didn't leave the boy until his mother turned up.直到这孩子的母亲来,我才离开。 The noise of the street didn't stop until it was midnight.街上的噪音直到半夜才停止。
3. until和before的区别
Before表示“在...之前”，而until表示“直到…才…”
1) 可直接换用的情况：在until能使用的句型中，即主句含有否定式终止性（短暂性）
谓语动词 (open, start, leave, go, arrive, finish, begin, stop) 或肯定式延续性动词 (stand, live, stay, talk, be, wait)，可与before直接替换,意义差别不大。
The students won't go home until / before they finish their homework.学生们要先完成作业才能回家。
The woman worked in the factory until/before 1990. 1990年以前这妇女在这家工厂上班。
2) 不可换用的情况：
当主句含有肯定式终止性（短暂性）谓语动词时，只能用before不能用until，且before常意为“没来得及……”或“……才……”等。
Einstein almost knocked me down before he saw me.爱因斯坦差不多将我撞倒才看见了我。
He had measured me before I could get in a word.我还没来得及插话,他就把我的尺寸量好了。
主句谓语动词强调动作的迟缓性，只用before，这时常伴有时间段状语或时间段暗示。
It was quite a long time before he found the elephant.过了很长时间，他才找到大象。 We had walked a long way before we found some water.走了很长的路我们才找到水。 We had sailed for two days before we saw the land.航行了两天我们才发现陆地。 如果强调从句谓语动作未发生就发生主句谓语动作，只用before，这时常译为“未及（不等）……就……”
We can leave early in the morning before it gets too hot.趁天还不太热，我们上午早点离开。
I must write it down before I forget it.趁我还未忘，我必须把它记下来。 表示“与其说……倒不如……”,“与其……毋宁……”的意思时只用before
I would give up my job before I agree to be dismissed. 我与其被解雇还不如先辞职。 He will die of hunger before he steals.他宁愿饿死也不愿意去偷。 在某些特定句型中用before
It was (not) long before…（不久）过了很长时间才…
It will (not) be long before…（不到）要过很长时间才会… For example:
It will probably not be long before they understand each other. 他们大概过不久就会互相了解。
It was not long before the whole country rose up. 不久全国人民奋起反抗。
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3) 下列情况一般使用until
主句是持续性谓语动词时，肯定,否定都可以，但意义完全不同，肯定表示动作终止，而否定表示动作开始。
We discussed the problem until/before he came back. 我们一直讨论到他回来。 We didn’t discuss the problem until he came back. 我们一直等他回来才讨论问题。 Not…until…句型尽管在某些情况下可与before互换使用，但在强调句中一般仍用until。
It was not until he told me that I knew it.直到他告诉我我才知道这件事。
It was not until he finished his homework that he went home.直到完成作业他才回家。 放于句首时用until
Until he finished his homework, he didn’t go home. 直到完成作业他才回家。
4. until和unless的区别
1) 作为从属连词含义不同,引导从句性质不同
unless与until均为从属连词，unless表“除非”,强调条件，引导条件状语从句；until表“直到”,强调时间的延续。引导时间状语从句。
I didn't know the news until my teacher told it to me. （动词didn't know表明该句强调时间的延续，表“我不知道这消息”的状态一直延续到“老师告诉我”，因此应用until引导时间状语从句。）
—Was his father very strict with him when he was at school?
—Yes. He had never praised him until he became one of the top students in his grade. （表明“他爸爸从来没有表扬他”的状态一直延续到“他变成年级最好的学生之一”，因此也应用until引导时间状语从句。）
I couldn't know the news unless my teacher told it to me. （动词couldn't know表明该句强调条件，表“我不可能知道这消息,除非老师告诉我”，因此应用unless引导条件状语从句。）
2) 作为从属连词引导的从句常用一般现在时表示将来
unless引导的条件状语从句和until引导的时间状语从句常用一般现在时表示将来。 Don't come in unless you're invited to. 除非邀请你否则别进来。
Unless he comes, we won't be able to go. 除非他来，我们不可能去。 3) 作为从属连词引导的状语从句可转换为省略式句型
unless引导条件状语从句和until引导时间状语从句时，如果主从句主语一致（或主从句主语不一致，但从句主语为it），从句谓语部分含有be，可将从句主语和动词be省略，构成省略式句型。
I won't come to see you unless I am asked to. →
I won't come to see you unless asked to. 除非你邀请我,我才会来看你。 The soldiers will not cross the river unless they are ordered to. →
The soldiers will not cross the river unless ordered to. 除非接到命令，战士们不会过河。
PPT课件 until
