If + Present Tense ， S + will/shall + V

結構︰If+現在式，S+未來式

說明︰if 子句用現在式，表示須具備的條件，主句用未來式表示可能的結果，整句含意為如果，那么。will 用于所有的人稱，在 I 和 we 之后可用 shall 代替 will.若主句的主詞為 I 或 we 時，可以用 shall 代替 will.像 if necessary(如果需要)，if possible(如果可能)，if so(如果這樣)等固定詞組實際上是省略了的 if 子句。

If I lose my job， I will/shall go abroad. 如果我失業了，我就出國。

If I have a headache， I will take an aspirin. 如果我頭痛，我就服一片阿斯匹林。

If it rains， we will stay at home. 如果下雨，我們將待在家里。

If the weather clears， well go for a walk. 如果天晴，我們就去散步。

If the weather doesnt clear， we wont go for a walk. 如果天不晴，我們就不去散步。

Inflation may be rising， if (it is) so， prices will go up.

通貨膨脹率可能上升。如果是這樣，物價就會上漲。

If possible， She wants to go with us. 可能的話，她想跟我們一起去。

Sterling may fall， if (this should be) so， interest rates will rise.

英國貨幣可能貶值，如果果真如此，利率就會上升。

If + Present Tense ， S + Modal Verb

結構︰If + 現在式，主詞+情態助動詞

說明︰本句型實為句型之變體。之所以用情態助動詞，主要是因為說話者對可能的結果不是太肯定或者是想表達例如必要的意思。

If it is fine tomorrow， we can go out. 如果明天天氣好，我門可以出門。

If it is fine tomorrow， we could go out. 如果明天天氣好，我門能夠出門。

If it is fine tomorrow， we may go out. 如果明天天氣好，我門可能出門。

If it is fine tomorrow， we might go out. 如果明天天氣好，我門可能出門。

If it is fine tomorrow， we should go out. 如果明天天氣好，我門宜于出門。

If it is fine tomorrow， we ought to go out. 如果明天天氣好，我門宜于出門。

If it is fine tomorrow， we must go out. 如果明天天氣好，我門必須出門。

If I should ， Imperative Sentence.

結構︰If I+should +祈使語氣

說明︰代替，增加了條件的不確定性。本句型常用在想禮貌地提出要求或建議，或者想圓通地告訴他人該做什么事的場合。用 should 起始句子即可不用 if 而表示條件。這種用法比較正式，常用于諸如公函之中，而不用于日常會話。

If you should see him， please give him my regards. 如果你見到他，請代我向他致意。

Should you see him， please give him my regards. 如果你見到他，請代我向他致意。

If you should happen to see him， please give him my regards.

如果你萬一見到他，請代我向他致意。

Should you happen to see him， please give him my regards.

如果你萬一見到他，請代我向他致意。

If you should write to her， send her my love. 如果你給她寫信，請代我向她問候。

Should you not wish our agent to call， please let us know.

你若不希望我們的代理人去造訪，請告之。

Should you be interested in our offer， please contact us.

你若對我們的報價感興趣，請與我們聯系。

If I should ， I will

結構︰Ifshould，would(will)/should(shall)等+原形動詞

說明︰這是表示與未來事實相反的假設句型，if 子句要用助動詞 should，譯成萬一。should可置于主詞前，將 if 省略。主要子句助動詞則視可能性做變化：若可能性低，則為過去式，若可能性高，則為現在式。should 可以提前，而將 if 省略。

If he should come， I would tell him the truth. 萬一他來，我會把真相告訴他。

If he should come， I will tell him the truth. 萬一他來，我一定會把真相告訴他。

Should the boy come again， I would throw him out. 要是那男孩在來，我就把他攆出去。

If it should rain， our plan would be spoiled. 萬一下雨，我們的計劃就泡湯了。

Should that be true， the contract would be canceled. 假如那是真的，合約就該取消。

Should another world war break out， what would become of human beings?

萬一另一次世界大戰爆發，人類將會發生什么事?

If I were to ， I

結構︰Ifwere to，would/should 等+原形動詞

說明︰這也是表示與未來狀況相反的假設句型，與if should， 大致相同，但if were to所表示的可能性更低，通常用以表示與真理相反的假設語氣.

If the sun were to rise in the west， he would pass the exam.

要是太陽從西邊出來，他就會通過考試他不可能通過考試。

If I were to be born again， I would like to be a bird. 我要是再活一次，我想當一只鳥。

If the sun were to disappear， what would the earth be like?

萬一太陽消失了，地球會變成什么樣子?

Were I to die tomorrow， what would my children do?

萬一明天我死了，我的孩子們將怎么辦呢?

If I + V-ed， I would

結構︰If+過去式動詞，主詞+過去式助動詞(would/should 等)+原形動詞

說明︰這是與現在事實相反的假設句型。if 子句中的 動詞，不論主詞為第幾人稱，一律用 were，were 可置于主詞前面，而省略 if.過去式助動詞除用 should(用于第一人稱)、 would(用于第二、三人稱)外，還可用不分人稱的 could，might 和 ought to，它們與動詞原形結合起來構成假設語氣.

If I knew his address， I could write to him. 如果我知道他的住址，我會寫信給他。

If I were free now， I might call on him. 如果我有時間，我可能會去看他。

If you were in my shoes (=Were you in my shoes)， what would you do?

如果你站在我的立場，你會怎么做?

Were I rich enough， I would buy a sports car. 如果我有足夠的錢，我就買一輛賽車了。

How happy I would be if I were a few inches taller! 要是我再高幾寸，我會好高興。

If I had a car， I could take her for a drive. 如果我有車， 我就帶她去兜風了。

If I had binoculars， I could see that comet clearly.

如果我有望遠鏡，我就可以清楚地看見那顆彗星。

It is time that

結構︰It is(high)time+(that)+主詞+過去式動詞

說明︰此句型意為已經到了的時間了。過去式動詞處有時亦使用should+動詞原形。that 子句也能用 to 不定詞來表示。

It is time he went to bed. 該是他睡覺的時間了。

It is time that you left for the duty. 該你當班了。

It is time that you reflected upon your mistakes. 該是你反省思過的時候了。

It is high time he should come to our house for dinner.已經到了他該上咱家吃晚飯的時候了。

It is time for somebody to teach you to behave yourself.

該是有人教你應對進退之禮儀的時候了。

If I had V-ed， I would have

結構︰Ifhad+過去分詞，主詞+would/should 等+have+過去分詞

說明︰這是與過去事實相反的假設句型子句要用過去完成式主要子句則要用過去式助動詞 (would，should，ought to，might，could)+have+過去分詞子句中的 had可置于主詞前面，而省略 If.

If I had seen him， I would have told him the truth. 如果我當時看見他，我會告訴他實情。

I could have finished the task if I had had more time.

如果當時我能有多一點時間，我就能完成這項任務。

If we had known of your departure， we would have seen you off at the airport.

如果我們事先知道你要離開，我們會到機場送行。

I someone had been with him， he might not have been drowned.

如果有人在他旁邊，或許他就不會溺死。

I might have been incredulous had I not been accustomed to such responses.

若非我已經習慣了這樣的回答，我可能不敢輕易相信。

Had he not apologize to her， she would not have forgiven him.

她(那時)不會原諒他，若非他道了歉。

Had he not saved me， I might have been drowned. 我可能溺死了，若非他救了我。

Had I proposed to you， would you have married me?

我要是當年向你求婚，你會答應嫁給我嗎?

Had you not helped us， we should have canceled this transaction.

假如沒有你的幫助，這筆生意早就告吹了。

If I had V-ed， I would

結構︰Ifhad+過去分詞，主詞+would/should 等+原形動詞+now/today

說明︰這是時態不一致時的假設句型，亦稱混合假設條件句。即：if 子句若與過去事實相反，用過去完成式而主要子句若與現在事實相反，則用過去式助動詞表示。此類主要子句句尾通常有表現在的時間副詞，如 now，today 等。

If he had worked harder when young， he would be well off now.

如果他年輕時多努力一點，現在就能過得舒服些。

If I had been rich ten years ago， I could buy that house today.

如果十年前我有錢，今天我就能買下那棟房子了。

Had he told the truth， he wouldnt be punished now.如果他當時肯說實話，現在就不會受罪了。

Had he followed the doctors advice， he might be alive now.

當時他要是聽了醫生的建議，現在可能還活著。

I wish + V-ed

結構︰I wish+(that)+主詞+動詞過去式/過去完成式(had+過去分詞)

說明︰I wish 之后以 that 子句受詞時，該子句動詞一定要用假設語氣：若動詞用過去式，表示與現在事實相反的愿望;若用過去完成式，則表示與過去事實相反的愿望。I wish+that-子句的句型也可用I would rather+that-子句取代。而 I hope 之后以 that 子句受詞時，該子句用一般時態.

I wish there were meadows and lambs. 但愿有草地與小羊。

I wish I were as tall as you. 但愿我像你一樣高。

I wish he could tell us. 但愿他能告訴我們。

I wish (=I would rather) he could come tomorrow. 但愿他明天能來。

I wish you had not been caught in the rain yesterday. 但愿昨天你們沒有淋到雨。

I wish you had not told the truth. 但愿你沒有說實話。

I wish I had known you ten years ago. 真希望十年前就已經認識你。

If only + V-ed

結構︰If only+過去式/過去完成式

說明︰此句型意為要是就好了。用過去式，表示與現在事實相反;若用過去完成式，則表示與過去事實相反。

If only I had a rich father. 要是我有個有錢的爸爸就好了。

If only he had been here. 要是他當時在這兒就好了。

If only I had another chance. 要是我再有一次機會就好了。

as if/as though

結構︰as if/as though現在式/過去式/過去完成式

說明︰此句型意為彷佛好像一樣。as if，as though 是副詞連接詞，引導副詞子句子句中，可用現在式，以表示事實;也可用過去式或過去完成式，分別表示與現在或過去事實相反的假設語氣.

He speaks like that as if he doesnt want to attend the meeting.他那樣說話，似乎不想參加會議。

He walks as if he is drunk. 他走起路來好像他真的醉了。

He felt as if he almost wished to kill them. 他感覺彷佛幾乎要殺掉他們。

The baby opened the book as if he were able to read. 這個嬰兒打開書本彷佛他會念書。

The nurse attends on the patient as if he were her father.

這護士照顧這位病人彷佛在照顧她爸爸似的。

He ran into the room as if he had seen something terrible.

他跑進屋子，彷佛他看到什么可怕的東西。

She looks as if nothing had happened to her. 她當時看起來好像什么事都沒發生似的。

It seems/looks as if

結構︰It seems/looks as if

說明︰此句型意為似乎。本句型中的 as if 子句可用以表示事實，或假設語氣.

It looks as if it is going to rain. 好像要下雨了。

It seems as if he knows everything. 他似乎是個萬事通。

It seems as if he knew everything， but in reality， he is as stupid as can be.

他似乎是個萬事通。其實他是再愚蠢不過了。

It looks as if she had just come back from outer space.

她看起來彷佛剛從外層空間回來似的。

It seemed as if he had finished the work. 他似乎已經完成了這個工作。

It seemed as if he would never finish the work. 他似乎永遠完成不了這個工作。

If it were not for

結構︰if it were not for+名詞/子句，主詞+would/should 等+原形動詞

說明︰此句型意為若非(有)。此類句構專門用于表示與現在事實相反的假設語氣.亦可用but for+名詞或without+名詞代替。were 可以提前，省略 if，如例句3.

If it were not for his presence， I would punish you. 要不是他在場，我會處罰你的。

But for your advice， I should have failed. 要不是你的忠告，我會失敗的。

But for music (=Were it not for music)， life would be dull. 要不是音樂，人生會很無聊。

If it were not for oxygen and nitrogen in the air， no man could live on the earth.

大氣中如果沒有氧和氮，人就無法生存于地球了。

Without air， all living things would die. 若非空氣，所有的生物都會死亡。

Without newspaper， we would get behind the times. 要不是報紙，我們都趕不上時代了。

I should be lonely， were it not for the birds and the flowers. 我會寂寞，若非有鳥也有花。

Were it not for his help， I could not finish the work.若非有他的幫助，我就不能完成這件工作。

Were it not for science， we could not live a comfortable live.

若非科學，我們無法過著舒適的生活。

If it had not been for

結構︰if it had not been for+名詞/子句，主詞+would/should 等+原形動詞