The modal verb NEED should not be confused with the notional verb TO NEED. The latter is used with auxiliary verbs, has non-finite forms and takes direct objects: Do you need me today?
The modal verb NEED maybe used either as a defective or as a regular verb.
Needas a defective verb has only one form, wich is unchanged in reported speech. It’s followed by the infinitive without “to”: Need I repeat it?
As a regular verb NEED can have all the necessary forms, including the verbals. It’s followed by the infinitive with “to”: Did you need to do it?
The use of this NEED is less common than of the defective NEED.
MEANING
1. absence of necessity(=Have): We don’t have to buy books.
2. permission not to do smth: You needn’t wait for me.
Notes
1. Need is used in interrogative and negative sentences.
2. Need expresses absence of necessity in negative sentences. When reference is made to the present or future it is followed by the indefinite infinitive. We needn’t go into detail.
In combination with the perfect infinitive NEED shows that an unnecessary action was done. It implies a waste of time and effort: You needn’t have come. We managed to do everything without your help.
Didn’t need or did not have followed by the infinitive simply shows that there was no necessity for the action in the past without showing whether the action was performed or not: He didn’t need/have to buy the dictionary.
3. In interrogative sentences NEED is used to ask about the necessity of an action. Asking about necessity to do smth, we can use both MUST and NEED.
NEED is used when the speaker hopes to get a negative answer: Need I wait for her now?
MUST is used when the seaker doesn’t know what answer to expect: Must I wait for her now?
-Need he come too?
-No, he needn’t (=He may but it is not necessary: permission not to do smth)
-No, he mustn’t (=It is not allowed: prohibition)
