until一词在中学阶段出现的频率较高,因而突破它在使用上的三个难点显得尤为重要。现分述如下:

一、until与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。如:

①I will finish my task by nine.我将在九点钟前完成任务。

②The 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。

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。如:

③I waited until he came back.我一直等到他回来。

④The 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。如:

⑤I didn't leave the boy until his mother turned up.直到这孩子的母亲来,我才离开。

⑥The noise of the street didn't stop until it was midnight.街上的噪音直到半夜才停止。

二、until与before的区别

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谓语动词或肯定式延续性动词,可与before直接替换,意义差别不大。如:

①The students won't go home until / before they finish their homework.学生们要先完成作业才能回家。

②The 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。如:

③Einstein almost knocked me down before he saw me.爱因斯坦差不多将我撞倒才看见了我。

④He 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。

三、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:

①Not until the teacher came in did the students stop talking.直到老师进来学生们才停止讲话。

②Not until next week will the sports meet be held.直到下周才开运动会。

2. not until的强调结构为:It is / was not until+从句/表时间的词+that+...。上面两句改为强调句为:

③It was not until the teacher came in that the students stopped talking.

④It is not until next week that the sports meet will be held.