2021屆高三英語詞匯短語復習
虛擬語氣在主從復合句中的用法
在狀語從句中的用法
條件句中的用法
虛擬語氣的條件句是用謂語動詞的特殊形式來表現(xiàn)與現(xiàn)在、過去事實相反的情況或?qū)戆l(fā)生的情況表示懷疑，和直陳語氣條件句中的謂語動詞形式以及表達的含義完全不同。虛擬語氣條件句中所用的謂語動詞的過去時、過去完成時、過去將來時等，只表示不同的虛擬語氣，和直陳語氣的過去時、過去完成時、過去②用法：
if i had more time, i should study german.(fact:i have no more time, so i shall not study german. )
if she were not so busy, she would attend the meeting this afternoon.(fact:she is very busy, so she will not attend the meeting this afternoon.)
if they didn’t take physical exercises every day, they wouldn’t be so healthy.(fact: they take physical exercises every day, so they are very healthy.)
②用法：
i would have checked my paper again if i had had more time at yesterday’s examination.(fact:i had no more time at yesterday’s exam, so i didn’t check my paper again)
you would have already recovered from his illness if he had seen the doctor in good time.(fact: he didn’t see the doctor in good time ,so he hasn’t recovered from his illness )
②用法：
if it rains tomorrow, our picnic will be put off.(the weather has been changeable these days.)
if it rained tomorrow, our picnic would be put off.( the weather has beenvery good these days.)
if it should rain tomorrow, our picnic would be put off.(that would be out of our expectation.)
if it were to rain tomorrow, our picnic would be put off. (條件從句謂語動詞用were to +動詞原形，表示 下雨的可能性極小。were to rain和should rain 都表示“出乎意料之外”，但were to加強表示“當初沒想到以后的事”)
混合時間條件句的用法：
有時條件從句的動作和主句動作發(fā)生的 時間不一致。這時動詞的形式，應(yīng)根據(jù)它所要表達的具體時間來決定用什么形式。
if she hadn’t trained so hard, she wouldn’t be run so fast.（從句敘述過去，主句敘述現(xiàn)在。）
（fact: she has trained very hard, so she would able to run fast.）
you would speak english well enough if you had practised reading and speaking it every day.(主句敘述現(xiàn)在，從句敘述過去)
（fact: you didn’t practice (hasn’t practiced ) reading and speaking it every day, so you can’t speak english well enough.）
在其他狀語從句中的用法
主要用于由as if (as though) 引導的比較狀語從句，從句中謂語動詞一般用“動詞的過去式（be 變were ）或had +過去分詞。”
如：
she looked as if she were ill.(實際上她沒有病，在這里用虛擬語氣補語比喻她精神不佳)
xiao liu speaks english so well as if he had studied in england.(這里用虛擬語氣表現(xiàn)他的 英語說得好)
（2）、在主語從句中的用法：
通常由形式主語it引出的主語從句來表達。主語從句中，謂語動詞用“should+動詞原形”；表示“必要”“重要”“奇怪”等意思。