VOA一分钟英语：Until 和 by 的用法

本集 “一分钟英语” 介绍用来说明动作发生时间的词语 —— “until” 和 “by”。虽然这两个词都可以译成 “到……时”，但它们的用法却不同。“Until” 表示某事在未来的某个时间点前持续发生；“by” 表示某事在未来某个时间或最后期限前发生。
 
Hi, guys! This is Kee from BBC Learning English. And today, I'm going to tell you the differences between until and by.
We use until to talk about doing something up to a certain point in time. If I say: 'I have to take care of my dog until 5pm', it means I will start taking care of my dog now and stop taking care of it at 5pm.
On the other hand, we use by to talk about doing something before a future time or a deadline. If I say: 'I have to finish an essay by 5pm', it means I can start any time, but I will make sure that at 5pm I have finished writing the essay. So, I may even finish it at 3pm or any time before 5.
So, we use until to describe doing something up to a certain point in time, and we use by to describe doing something before a future time or a deadline. 
 
用法总结
1 Until
Until is used to talk about doing something up to a certain point in time.
“Until” 用来表示 “在某个时间点之前，一直做某事”。
I have to take care of my dog until 5pm.
Until the rain stops, we can't go to the beach.
I will be working until this evening. We can meet for dinner after that. 
 
2 By
By is used to talk about doing something before a future time or deadline.
“By” 用来表示 “在未来某个时间或最后期限之前做某事”。
I have to finish an essay by 5pm.
The council expects the bridge to be finished by December.
By the time I come back, I want this room clean.