Need expresses necessity. It is mostly used in negative and interrogative sentences.
You needn’t be in such a fright. Take my arm. (Shaw)
NOTE: When need is used in the meaning of ‘to be in want of’ it is treated as a normal verb. e.g. He needs a new pair of shoes.
Need has only one tense form — the Present. In the same way as dare, need is used as a normal and as an anomalous verb; the latter is much more common in colloquial English.
One need to be careful. (Zandvoort)
He did not need to be told twice. (Zandvoort)
Why need he bother us? (Knuslnga)
I am here. You needn’t be afraid. (Greene)
I need hardly say I would do anything in the world to ensure Gwendolen’s happiness. (Wilde)
Need is used both with the Indefinite and with the Perfect Infinitive. I suppose I needn’t have made that observation. (Pinero)