介詞 until (till) 與 by 的用法區(qū)別

用作介詞的 until（包括 till）和by，均可表示“在某時之前并不晚于某時的任何時間”，使用時注意以下幾點：

1. until / till 通常只與表示一段時間的“持續(xù)動詞”（如stay, wait）連用時。如：

She stayed until noon. 她呆到中午才走。

It may last till Friday. 這可能要延續(xù)到星期五。

I remain in London until May. 我在倫敦一直呆到五月。

We talked until midnight and then separated. 我們一直談到深夜才分手。

It was his intent to leave at 6:30, but he stayed until 8:00. 他本打算六點半離開，但是他一直呆到八點。

We are counting down the days until the end of the exams. 我們倒數(shù)著日子，一直數(shù)到考試結(jié)束。

注：若所用動詞只表示一時點（如finish, leave），則只能在否定句中用till / until。如：

You mustn’t open this parcel until Christmas Day. 圣誕節(jié)前你絕不能打開這個包裹。

We got home at 6 o’clock, but the other didn’t get back until 10. 我們6點鐘到家，而另外幾個l0點才回來。

He promised to be here at four o’clock but didn’t appear until six. 他答應(yīng)四點鐘來，可是六點鐘才到。

I arrive at the hospital at eight o’clock, but I don’t go on duty until nine. 我八點鐘就到醫(yī)院了, 但是九點鐘我才去值班。

Women were not given the franchise in Britain until the twentieth century. 英國婦女直到二十世紀(jì)才獲得選舉權(quán)。

2. 介詞 by 通常只與表時點的動詞連用。如：

She’ll have retired by then. 她到那時就要退休了。

We had hoped to finish by four o’clock. 我們原希望四點鐘前能完成。

I’ll have left by Monday. (=any time before and not later than) 到星期一我就已離開了。(=在星期一前不晚于星期一的任何時間)

You’ll have to shift if you want to get there by nine o’clock. 你要想九點鐘到那兒, 就得快點。

We’re in big trouble if we don’t come up with the money by 6 o’clock. 如果我們6點之前拿不出錢來，麻煩就大了。

注：有些表示狀態(tài)的動詞在某些特殊搭配或語境可以表示“時點”，則此時也可與 by 連用。如：

As a rule I’m home by six. 此句應(yīng)理解為“我通常六點鐘到家”（相當(dāng)于As a rule I get home by six.），不能理解為“通常六點鐘前我待在家里”。

She worked hard so that everything would be ready by 6 o’clock. 此句應(yīng)理解為“她拼命干以便能到6點時把一切都準(zhǔn)備好”（相當(dāng)于She worked hard so that everything would get ready by 6 o’clock.），不能理解為“她拼命干以便能到6點時一切都一直是準(zhǔn)備好的”。

其他例句如(www.hz123456.com)：

We shall be back by six o’clock. 我們六點鐘回來。

The children must be back by 4 o’clock. 孩子必須4點鐘以前回來。

I drove home to him that he must be here by ten. 我跟他說得清清楚楚：他必須十點鐘以前到這里。

3. 當(dāng)與表時點的動詞連用且用于否定句時，兩者都可以用。如：

I won’t have left by Monday. (=I’ll still be here on Monday) 我星期一前不會離開的。(=我星期一還在這兒)

We got home at 6 o’clock, but the others didn’t get back until 10. 我們6點鐘到家，而另外幾個l0點才回來。

Might I enquire why you have not mentioned this until now? 請問你為什么直到現(xiàn)在才提及此事呢？