WordReference Collins English Usage © 2019
Need has the negative forms need not and do not need. The contracted forms needn't and don't need are also used. However, you cannot use all these forms for all meanings of need. This is explained below.
used as a transitive verb
If you need something, it is necessary for you to have it.
These animals need food throughout the winter.
He desperately needed money.
For this meaning of need, the negative form is do not need.
You do not need special tools for this job.
I don't need any help, thank you.
I didn't need any further encouragement.
Be careful
Don't use a progressive form of ‘need’. Don't say, for example, ‘We are needing some milk’. Say ‘We need some milk’.
used as an intransitive verb or modal
If you need to do something, it is necessary for you to do it.
You'll need to work hard to pass this exam.
For an answer to these problems we need to look elsewhere.
You must use to in sentences like these. Don't say, for example, ‘You’ll need work hard to pass this exam'.
questions and negatives
In negative statements you usually use do not need to. You say, for example, ‘He doesn’t need to go'. You can also use need not as the negative form. For example, you can say ‘He needn’t go'. However, this is less common and more formal. Don't say ‘He doesn’t need go' or ‘He needn’t to go'.
You don't need to shout.
You needn't talk about it unless you want to.
In questions, you almost always use do and need to. You usually only use need on its own in a few set phrases, such as ‘Need I say more?’ and ‘Need I remind you?’
Do you need to go?
Need I remind you that you owe the company money?
‘must not’
If you tell someone that they don't need to or need not do something, you are saying that it is not necessary for them to do it. If you want to say that it is necessary for someone not to do something, don't use ‘need’. Instead you use must not or mustn't.
You must not accept it.
We mustn't forget the tickets.
➜ See must
talking about the past
If you want to say that it was not necessary for someone to do something at a time in the past, you say that they didn't need to do it or they didn't have to do it. Don't say that they ‘needn’t' do it.
I didn't need to say anything at all.
Fortunately, she didn't have to choose.
However, in a reporting structure you can use needn't.
They knew they needn't worry about me.
If someone has done something and you want to say that it was not necessary, you can say that they needn't have done it.
I was wondering whether you were eating properly, but I needn't have worried, need I?
‘need’ with -ing forms
You can use need with an -ing form to say that something should have something done to it. For example, you can say ‘The cooker needs cleaning’, rather than ‘The cooker needs to be cleaned’.
The plan needs improving.
We made a list of things that needed doing.
'need' also found in these entries:

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