As a preposition of time, “by” means before a specific time.

作為放在時間前的介詞，by的意思是在特定的時間之前。

“by” shows a time limit for something to happen.

by展示出了某事發(fā)生的時間范圍限制。

An event must happen before a specific time is reached.

就是事件必須在到達特定時間之前發(fā)生。

例：

Please send me the report by Tuesday.

請在星期二之前把報告發(fā)給我。

(I must receive it before Tuesday. The deadline is Tuesday 我必須在星期二之前收到。截止日期是星期二)

Jane would like to lose 3 kg by June.

簡想在六月前減重3公斤。

(She would like to lose 3kg before June.)

她想在六月前減掉3公斤。

We often use “by” for projects with deadlines.

我們經(jīng)常用by在項目的最后期限前。

All job applications must be received by the 15th July.

所有工作申請必須在7月15日前收到。

We often use “by” to say when someone will return:

我們經(jīng)常用by來表示某人什么時候回來

例：

Mark: Where is Jane?

簡在哪里？

David: She is in London. She’ll be back by Saturday.

她在倫敦。她將在星期六之前回來。

As a preposition of time, “until” describes a continuous action that stops at a specific time.

作為時間介詞，until描述一個在特定時間停止的連續(xù)動作。

“until” describes the duration of an action before a specific time.

until描述動作在特定時間之前的持續(xù)發(fā)生。

例：

I’m staying in New York until Friday.

我要在紐約待到星期五。

I’m really tired. Last night I watched a film until midnight.

我真的很累。昨晚我看了一場電影直到午夜。

Mark lived in Manchester until 2010.

2010年之前，馬克一直住在曼徹斯特。