Until和by的用法，尽管“until”和“by”这两个词用能够翻译成“到……时”，但他们的使用方法却不一样。“Until”表明某件事在未来的某一时间点前不断产生；“by”表明某件事在未来某一時间或最终限期前产生。

1 Until

Until is used to talk about doing something up to a certain point in time.

“Until” 用于表明 “在某一时间点以前，一直做某件事”。

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” 用于表明 “在未来某一時间或最终限期以前做某件事”。

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.