saying that something is forbidden: will not
5.147 Will not is used to tell someone very firmly that they are not allowed to do a particular thing. Usually, the speaker has the power to prevent the hearer from doing this thing.
‘I’ll just go upstairs.’ – ‘You will not.’
Until we have cured you, you won’t be leaving here.
saying that something is forbidden: shall not
5.148 Shall not is used to say formally that a particular thing is not allowed. Shall not is often used in written rules, laws, and agreements.
Persons under 18 shall not be employed in nightwork.
Equality of rights under the law shall not be denied or abridged by the United States or by any State.
Shan’t is used in a similar way to will not and won’t.
You shan’t leave without my permission.
saying that something is forbidden: imperatives
5.149 You can also say that something is not allowed by using an imperative sentence. Imperative sentences are explained in paragraph 5.4 and in paragraphs 5.35 to 5.39.
undesirable actions: should not
5.150 Should not is used to tell someone that an action is unacceptable or undesirable.
You should not take her help for granted.
You shouldn’t do that.
You shouldn’t be so unfriendly.
undesirable actions: must not
5.151 Must not is used to say much more firmly that something is unacceptable or undesirable.
You must not accept it.
You mustn’t do that.
You mustn’t breathe a word of this to anyone.
Interacting with other people
5.152 You often say things in order to get someone to behave in a particular way. For example, you may want someone to take a particular action, to accept an offer, or to give their permission for something to be done.
In these situations, modals are often used. The modal you choose depends on several factors. The main ones are:
In particular situations, other factors can be important. For example, if you are making an offer or suggestion, the modal you choose may depend on how persuasive you want to be.
5.153 The following sections explain how to use modals in different situations.
Paragraphs 5.154 to 5.170 explain how to give instructions and make requests.
Paragraphs 5.171 to 5.179 explain how to make an offer or an invitation.
Paragraphs 5.180 to 5.187 explain how to make suggestions.
Paragraphs 5.188 to 5.193 explain how to state an intention.
Paragraphs 5.194 to 5.199 explain how to express unwillingness or a refusal to do something.
Paragraphs 5.200 to 5.208 explain how to express a wish.
Paragraphs 5.209 to 5.213 explain how to indicate the importance of doing something.
Paragraphs 5.214 to 5.220 explain various ways of introducing what you are going to say.
Giving instructions and making requests
5.154 When you give an instruction or make a request, you usually use a modal in an interrogative sentence.
You use will, would, can, or could with you to tell someone to do something, or to ask someone to do something.
You use can, could, may, or might with I or we or with other personal pronouns or noun phrases to ask someone’s permission to do something.
Instructions and requests are always made more polite by adding please. Please and other markers of politeness are explained in paragraph 5.170.
instructions and appeals for help
5.155 Will, would, and could are used with you in two ways:
instructions and appeals for help: will
5.156 Will is used to give an instruction or order in a fairly direct way. It is slightly less forceful than using the imperative.
Will you pick those toys up please?
Will you pack up and leave at once, please.
Will is used to ask for help in fairly informal situations.
Mummy, will you help me?
instructions and appeals for help: would
5.157 When would is used to give an instruction or order, it is more polite than will.
Would you tell her that Adrian phoned?
Would you ask them to leave, please?
When would is used to ask for help, it is less informal and more polite than will.
Would you do me a favour?
instructions and appeals for help: could
5.158 When could is used to give an instruction or order, it is more polite than would.
Could you follow me please?
Could you just switch the projector on behind you?
When could is used to ask for help, it is more polite than would.
Could you show me how to do this?
appeals for help: can
5.159 Can can be used with you to ask for help. You usually use can when you are not sure whether someone will be able to help you or not.
Oh hello. Can you help me? I’ve been trying this number for ten minutes and I can’t get through.
requests
5.160 Can, could, may, and might are used with I or we when you are asking for something, or are asking permission to do something.
These modals can also be used with he, she, or they, or with other noun phrases, when you are asking for something on behalf of someone else. For example, you can say Can she borrow your car? or Could my mother use your telephone?