1． 在非真實(shí)條件句中，有時(shí)從句的動(dòng)詞所表示的動(dòng)作和主句的動(dòng)詞所表示的動(dòng)作并不同時(shí)發(fā)生，這樣的條件句中使用的虛擬式稱為混合虛擬式。其構(gòu)成視具體情況而定。例如：
If I had taken my raincoat when I came out this morning, I would not be wet now.
If I were you, I wouldn’t have missed the film last night.
2．引導(dǎo)非真實(shí)條件從句的連詞if在正式文體中有時(shí)可以省去, were, had, had, should等非行為動(dòng)詞這時(shí)應(yīng)提到從句句首。例如：
If I were you, I wouldn’t feel sorry.
→Were I you, I wouldn’t feel sorry.
3．有些句子從表層結(jié)構(gòu)上看無if引導(dǎo)的非真實(shí)條件句， 但從深層意思上看是存在的。這種情況下主句動(dòng)詞仍需用虛擬式。這類句子中常出現(xiàn)without（如果沒有），but for（要不是），otherwise（否則），but that （若不，后接一從句）等詞或詞組。例如：
But for your help, they couldn’t have succeeded.
要不是你的幫助，他們就不會(huì)取得成功。
She wasn’t feeling well. Otherwise，she wouldn’t have left the meeting so early.
她感到不舒服。不然她就不會(huì)那么早就離開會(huì)場的。
4． 在It is + 形容詞 + that 從句的句型中，that引導(dǎo)的主語從句中的謂語動(dòng)詞采用should + 動(dòng)詞原形形式，其中should 常省略?？捎糜诖司湫偷男稳菰~還有：absurd, advisable, better, best, desirable, (un)fair, fortunate, good, imperative, important, incredible, just, natural, (un) necessary, odd, pleasant, possible, preferable, right, ridiculous, sad, silly, unusual, urgent, vital, wrong等，表示必要、應(yīng)該、建議、要求、驚訝、不相信等意。例如：
It’s necessary that we (should) set out at once.
It’s proposed that a committee (should) be set up to look into the matter.
5． 意為“提議、建議、請求、命令”等意思的動(dòng)詞所帶的從句（包括賓語從句和主語從句）中，謂語動(dòng)詞用should + 動(dòng)詞原形形式。美國英語多用動(dòng)詞原形，英國英語多用should + 動(dòng)詞原形。有相同用法的動(dòng)詞還有ask, advise, agree, arrange, beg, command, decide, demand, desire, determine, direct, instruct, insist, intend, maintain, move, order, persuade, pray, propose, recommend, request, require, stipulate, suggest, tell, urge。例如：
I suggest that we (should) go camping tomorrow.
He insisted that our laboratory reports (should) be handed in the day after the experiment was done.
他堅(jiān)持要求我們將實(shí)驗(yàn)報(bào)告在做完實(shí)驗(yàn)后第二天交上來。
應(yīng)當(dāng)注意的是當(dāng)suggest、insist等詞不再表示“建議”或“堅(jiān)持要求”的含義時(shí)，其后的從句不再用虛擬語氣。例如：
His look suggested that he wasn’t telling the truth. 他的神色表明他沒講實(shí)話。
He insisted that he was right. 他堅(jiān)持認(rèn)為他是對的。
If I had taken my raincoat when I came out this morning, I would not be wet now.
If I were you, I wouldn’t have missed the film last night.
2．引導(dǎo)非真實(shí)條件從句的連詞if在正式文體中有時(shí)可以省去, were, had, had, should等非行為動(dòng)詞這時(shí)應(yīng)提到從句句首。例如：
If I were you, I wouldn’t feel sorry.
→Were I you, I wouldn’t feel sorry.
3．有些句子從表層結(jié)構(gòu)上看無if引導(dǎo)的非真實(shí)條件句， 但從深層意思上看是存在的。這種情況下主句動(dòng)詞仍需用虛擬式。這類句子中常出現(xiàn)without（如果沒有），but for（要不是），otherwise（否則），but that （若不，后接一從句）等詞或詞組。例如：
But for your help, they couldn’t have succeeded.
要不是你的幫助，他們就不會(huì)取得成功。
She wasn’t feeling well. Otherwise，she wouldn’t have left the meeting so early.
她感到不舒服。不然她就不會(huì)那么早就離開會(huì)場的。
4． 在It is + 形容詞 + that 從句的句型中，that引導(dǎo)的主語從句中的謂語動(dòng)詞采用should + 動(dòng)詞原形形式，其中should 常省略?？捎糜诖司湫偷男稳菰~還有：absurd, advisable, better, best, desirable, (un)fair, fortunate, good, imperative, important, incredible, just, natural, (un) necessary, odd, pleasant, possible, preferable, right, ridiculous, sad, silly, unusual, urgent, vital, wrong等，表示必要、應(yīng)該、建議、要求、驚訝、不相信等意。例如：
It’s necessary that we (should) set out at once.
It’s proposed that a committee (should) be set up to look into the matter.
5． 意為“提議、建議、請求、命令”等意思的動(dòng)詞所帶的從句（包括賓語從句和主語從句）中，謂語動(dòng)詞用should + 動(dòng)詞原形形式。美國英語多用動(dòng)詞原形，英國英語多用should + 動(dòng)詞原形。有相同用法的動(dòng)詞還有ask, advise, agree, arrange, beg, command, decide, demand, desire, determine, direct, instruct, insist, intend, maintain, move, order, persuade, pray, propose, recommend, request, require, stipulate, suggest, tell, urge。例如：
I suggest that we (should) go camping tomorrow.
He insisted that our laboratory reports (should) be handed in the day after the experiment was done.
他堅(jiān)持要求我們將實(shí)驗(yàn)報(bào)告在做完實(shí)驗(yàn)后第二天交上來。
應(yīng)當(dāng)注意的是當(dāng)suggest、insist等詞不再表示“建議”或“堅(jiān)持要求”的含義時(shí)，其后的從句不再用虛擬語氣。例如：
His look suggested that he wasn’t telling the truth. 他的神色表明他沒講實(shí)話。
He insisted that he was right. 他堅(jiān)持認(rèn)為他是對的。