Need is used both as a principal verb and as an auxiliary:
When need is used as a principal verb, it means ‘require’.
- He needs my help.
- We need two more players for the team.
- We have got what we need.
- He needed some more time to decide the question.
When need is used as an auxiliary verb, its form remains the same whatever be the number or person of the subject. The auxiliary need is common in questions and negatives.
- He need not ask my permission.
- He need not wait any longer.
- They need not make such a fuss over it.
- You need not mention this to anyone else.
Sometimes it is used with hardly:
- I need hardly say that I am very grateful.
- We need hardly remind you of your promise to visit us.
- I need hardly add that you are always welcome.
It can be used with only:
- He need only say what he wants and it will be granted.
- You need only sign this form and I shall do the rest.
- I need only add that we shall always remain indebted to you for your help.
Need is usually used in questions without ‘not’.
- Need he wait any longer?
- Need I come again?
- He need not wait any longer, need he?
If the answer is in the negative, we will say:
- ‘No, he / you / they need not.’
But if the answer is in the positive, you should say:
- ‘Yes, he /she / you must.’
The opposite of need not in such a context is not need but must.
Need without not is also used in the following kinds of statements:
- You need pay only 20 dollars.
- I don’t think we need copy all these figures.
- There need be no further correspondence on this matter.
When referring to Past time, need is followed by the perfect infinitive:
- He need not have lost his temper.
- They need not have come all this way.
- We need not have waited for his approval.