虚拟语气是通过谓语动词的特殊形式来表达的。另外表示主观愿望或表达某种强烈的感情时，也用虚拟语气。其在主语从句、宾语从句、表语从句、同位语从句、状语从句中有不同的用法。
1.主语从句中虚拟语气的用法
主语从句中的虚拟语气由 "should+动词原形 "体现，should可以省略，通常由it作为正式主语使用。表达的意思有以下几种：
①表示请求、建议、要求、命令、警告等。
It is / was advised / decided / proposed / requested / ordered / suggested等+ that...
It is suggested that parents (should) spend more time with their children athome. 在家里父母应该花更多的时间和孩子们在一起。
②表示应该、重要、必须等。
It is / was appropriate / essential / important / right / vital等+ that...
It was right that you (should) take the responsibility for him. 你为他承担责任是对的。
③表示惊讶、难以置信等。
It is / was strange / dreadful / suprising / unnormal / unthinkable / asurprise等 + that...
It was a surprise that he won the contest. 他竟然赢了比赛，这真令人惊讶。
2.宾语从句中虚拟语气的用法
①当主句中的动词是请求、要求、命令、建议、忠告等，如advice, ask, command, decide, demand, desire, insist, propose, recommend, require, suggest, urge等，从句的谓语采用虚拟语气should+动词原形，should可以省略。
It is / was strange / dreadful / suprising / unnormal / unthinkable / asurprise等 + that...It was a surprise that he won the contest. 他竟然赢了比赛，这真令人惊讶。
②当主句谓语动词为wish时，从句谓语使用虚拟语气。
我希望我是一只鸟。(Iwish you had come to my wedding. (我希望你明天能/愿意来参加我的生日聚会。(虚拟为未来，表达一种愿望)
③当主谓动词是would rather时，从属谓语使用虚拟语气。
I wish I were a bird. 我要是一只鸟儿多好。(对现在的虚拟)
I wish you had come to my wedding. 你要是来参加我的婚礼就好了。(对过去的虚拟，表示一种愿望和遗憾)
I wish you could / would come to my birthday party tomorrow. 但愿你明天能来参加我的生日派对。(对将来的虚拟，表达愿望)
3.虚拟语气在表语从句中的用法
①当as if/though引导的表语从句用于表达一种与当时事实不相符的事态或现象或想法时，该从句应使用虚拟语气。
It looks as if / though he were drunk. 他看起来像喝醉了。(但实际并没有醉)
It seemed as if / though the man had lost his way in his own village. 这个男人好像在自己的村子里迷路了。(但实际并没有迷路)
比较：It seemed as if / though the man lost his way. 这男人好像迷路了。(可能真的迷路了)
②当被从句修饰的名词是请求、建议、断言、决定、命令等，如advice，suggestion，demand，proposal，requirement，order等，从句谓语要用虚拟语气。
My suggestion is that we (should) take a taxi instead of a bus. 我的建议是我们打车而不是坐公交。
