英文法、 9.假設語氣

  9.假設語氣

假設語氣：陳述假設或想像，而非事實，子句動詞不受時態限制

條件句：從屬連接詞的從屬子句加情態助動詞 (will, would, can, could, may, might)的主要子句

If-假設，將來有可能實現：If  現在簡單式 ,  S  + (will, can, may, might) +動詞原式

                If it rains, I will stay home.

               If I lie to her, she is going to slaughter me.    (be going to = will)

If-假設，與現在相反、否定： If  過去簡單式 ,  S  + (would, could, should, might) +動詞原式

               If I were you, then I wouldn't do that.

               If you asked her, she might help you.  (因為沒問 所以沒有幫忙)

               If John had enough money, he would buy the car.  

If-假設，與過去相反： 

                        If  +S had +過去分詞 ,  S  + (would, could, should, might) have +過去分詞

                If Jessie had asked me for help, I could have helped her.

                If David had been taller, he could have played in the NBA.

If-假設，未來不確定：   If  +S should + 原型 ,  S  + (would, will.....) 原型

                        低可能性-過去式助動詞：would, could, might, should, ought to

                        高可能性-現在式助動詞：will, can, may, should, ought to    

                The sky is blue. If it should rain, the picnic would be canceled.   (晴天)

                There are dark clouds in the sky. If it should rain, the picnic will be canceled. (陰天)

        * If假設都可倒裝

    

                You will pass the exam if you study hard.

                 I would buy a house if I won the lottery.

                 I would have passed the exams if I had studied hard.

條件式事實：   If /  When /Unless +現在簡單式/進行式，現在簡單式

                If you heat ice, it melts.     When you heat ice, it melts.

                If I am driving, I never answer my cellular phone.

表時間的假設，未來將發生：

        S + (be going to / will)動詞原式 ，(before, after, when, as soon as, until) + S +現在簡單式

                We'll wait here until the bus comes.

與真理相反，否定假設：if +S were to，S (would, could, might, should, ought to)+原形動詞

                If the sun were to rise in the west, I would marry you.

提議、要求、命令等動詞後的that子句有要求性，應該用假設語氣+原形動詞

                

                I suggest that he study for the exam

                The boss requests that everyone be notified of the next meeting.

緊迫性形容詞後that子句接原形動詞

It is ( urgent, mandatory, crucial, essential, necessary, imperative ) that  原形動詞

**和現在事實相反，就用過去式。

**和過去事實相反，就用過去完成式。

8.助動詞    ↼   9.假設語氣   ⇀  10.動名詞、不定詞