祈使句是用来表示请求、命令、劝告或建议的句子.
①祈使句的主语一般为第二人称you,但通常省略,谓语动词用动词原形.祈使句的否定形式为：Don't+动词原形+…….祈使句的句末通常用句点.为了加强语气,也可以用感叹号.在表示客气的请求时,常在句首或句末加上please.please用在句末,前面加逗号.祈使句中如果有称呼语,要用逗号隔开,放在句首或句末.eg.
Please peel three bananas for me.请给我剥三个香蕉.
Be quiet,please.请安静.
Don't talk loudly in the classroom.不要在教室里大声喧哗.
Dave,come here.大卫,过来.
②含有第一、第三人称主语的祈使句,其肯定形式为：Let+第一人称（me,us）+…… ; Let+第三人称（him/her/it/them）或名词+……,其否定形式为：Let + sb.+not+动词原形+……/ Don't let + sb.+动词原形…….eg.
Let me have a try.让我试试.
Let Tom go there himself.让汤姆自己去那儿.
Don't let them play with fire.别让他们玩火.
在肯定祈使句之前可用助动词do 以加强语气,但这种结构只用于第一人称祈使句和第二人称无主语的祈使句.eg.
Do be quiet a moment.一定要安静一会儿.
Do let me go.一定让我去吧.
③祈使句除用谓语动词表示外,还可用名词、副词等表示.eg.
Help!救命!Patience!要有耐心!
Quickly!快!Hands up!举起手来!
注祈使句与陈述句的改写
祈使句=You must...eg.
Come here.= You must come here.
过来.你必须过来.
Don't do that again.(别再那样做了.) = You mustn't do that again.(你一定不要再那样做了.)
Please+祈使句=Will you (please)…?eg.
Please help me.(请帮帮我.) = Will you (please) help me?(你愿意帮我的忙吗?)
Come here on time,please.(请准时到这儿.) =Will you (please) come here on time?(请你准时到好吗?)