1 形式
祈使句是动词的基本形式。以第二人称构成语法规则。当我说Come in时，我的意思是“你应该进来”。否定词是do not/don't 基本形，如果强调，则使用do 基本形。
肯定句: Come in.
Read the instructions carefully.
否定句: Do not remove this book from the library.
Don't make so much fuss.
强调句: Do be careful.
注意=>我们可使用其他带否定意义的词来构成祈使句
Never touch electrical equipment with wet hands. Leave no litter.
2 用法a 祈使句的基本用法是“给出命令”让人做某事，说话者希望听话者能够遵守
老师命令学生: Get out your books, please.
医生命令患者: Just keep still a moment.
老板命令员工: Don't tell anyone about this.
交通标识: Stop.
b 但祈使语气听上去粗鲁且突然，这些句子也可表达“命令”：
I want you to just keep still a moment.
You must hand the work in by the weekend.
You mustn't tell anyone about this.
不那么粗鲁的表达命令的方式（请求的疑问句）：
Can you get out your books, please?
Could you just keep still a moment?
用请求表达命令更“安全”，但在同级别和同龄人之间常用祈使句
Give me a hand with these bags.
Hurry up, or we're going to be late.
注意=>当祈使句用来让人保持安静或走开时，听上去很粗鲁且不礼貌
Shut up. Go away - I'm busy. Get lost.
c 涉及一连串动作，请求表达不需要每个动作都重复使用
Can you get out your books, please? Open them at page sixty and look at the photo. Then think about your reaction to it.
宣传标语和广告:
Save the rainforests. Visit historic Bath.
暗示和建议:
Why don't you spend a year working before you go to college? Take a year off from your studies and learn something about the real world.
警告和提醒:
Look out! There's a car coming.
Always switch off the electricity first. Don't forget your key.
指示和方向:
Select the programme you need by turning the dial to the correct number. Pull out the knob. The light will come on and the machine will start. Go along here and turn left at the lights.
非正式的书面通知和邀请:
Have a chocolate.
Come to lunch with us.
美好的祝愿:
Have a nice holiday. Enjoy yourselves.
注意
Have a chocolate. = Would you like a chocolate?
Have a nice holiday. = I hope you have a nice holiday.
4 祈使句 疑问词标签祈使句后面可用这些标签：: will you? won't you? would you? can you? can't you? could you?
a 肯定标签用在一个肯定祈使句后面.
老师: Get out your books, will/would/can/could you?意义等同于Will you get out your books?但“标签模式”不是很正式.
否定标签表达更强的感觉.
医生: Keep still, won't/can't you?（这里暗示医生很焦虑希望患者能够保持安静，或很生气）
b 在警告，提醒和祝愿中，标签用won't you? 在肯定祈使句后用will you? 这些标签能够使句子更具“强调性”.
Have a nice holiday, won't you? Don't forget your key, will you?
In offers and invitations the tag is will you? or won't you?
Have a chocolate, will/won't you?
5 祈使句 一个主语我们能提醒主语you当它和另一个人对比时
I'll wait here. You go round the back.
表达强调的命令或更具侵略性
You be careful what you're saying.
注意
a 一些短语也可以作主语： All of you sit down! Everyone stop what you're doing.
b 否定词don't要放在主语前：Don't you talk to me like that.
6 Let让a Let's (= let us) 动词基本型表达一个建议.
It's a lovely day. Let's sit outside.（意思是“我们”应该坐外面）
Let's have some coffee (,shall we?).
Let's 暗示一个动作由说话者和听话者执行.
否定形是let's not 或 don't let's, 如强调用do let's.
否定: Let's not waste any time./Don't let's waste any time.
强调: Do let's get started. We've wasted enough time already.
注意
a 美式用法一般就用Let's not否定，而不用“Don't let's或Do Let's
b 完整形Let us更正式和古老.
Let us give thanks to God.
b Let me 意思是说话者正在告诉ta自己做什么
Let me think. Where did I put the letter?
Let me see what's in my diary. Let me explain.
Let me think 意思是 '我将去思考/给我点时间想一下.'
注意
Let 也有“允许”的含义.
Oh, you've got some photos. Let me see./May I see?
c let 后面可以跟一个名词短语.
Let the person who made this mess clean it up.
Let the voters choose the government they want. Let them decide. （Let them decide 意思是 '他们应该决定'.）
注意
还有2种特殊的句式可表祈使，比如“虚拟语气”和“may表愿望”（这2种表达更正式，且受语境的限制）
God save the Queen.（虚拟）
May your dreams come true.（may表愿望）
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